Characteristic Evaluation of Gas Chromatography with Different Detectors for Accurate Determination of Sulfur Hexafluoride.

Sulfur hexafluoride (SF6), which survives in the atmosphere for an extremely long period of time, is the most potent greenhouse gas regulated under the Kyoto Protocol. So, the accurate monitoring of atmospheric SF6 plays an important role in the study of the control policies for reducing greenhouse gas emissions. The instruments for SF6 measurement are typically calibrated using certified reference materials. The concentrations of the commercially available SF6 reference materials usually have a broad range, from 1 µmol/mol to 6000 µmol/mol. Some characteristics including sensitivity, linear range, relative standard deviation, and accuracy are crucial for the determination of SF6 in such a broad concentration range. Therefore, the selection of a proper detector for the accurate determination of SF6 with such a broad range is extremely important to establish a gas chromatography (GC) method for developing SF6 reference materials. In this paper, several typical GC methods with different detectors, including a thermal conductivity detector (TCD), a pulsed discharge helium ionization detector (PDHID), and a flame photometric detector (FPD), were carefully established for the accurate determination of SF6 with different concentrations. The results show that an FPD detector has a relatively narrow linearity range, thus a quadratic equation should be established for building a calibration curve. The PDHID and TCD have good linearity with coefficients of 1.0000 in the concentration range of 10-100 µmol/mol (using a PDHID), and 100-1000 µmol/mol (using a TCD), respectively. Further considering the measurement errors of indication results, the PDHID is suitable for SF6 measurement when the concentrations are below 100 µmol/mol, whereas the TCD is suitable for SF6 measurement when the concentrations are over 100 µmol/mol. These results provide useful guidance in choosing an appropriate GC detector for the accurate determination of SF6, which are especially very helpful for developing SF6 reference materials.

Copper neurotoxicity: Induction of cognitive dysfunction: A review.

Cognitive dysfunction occurs mainly in certain diseases and in the pathological process of aging. In addition to this, it is also widespread in patients undergoing anesthesia, surgery, and cancer chemotherapy. Neuroinflammation, oxidative stress, mitochondrial dysfunction, impaired synaptic plasticity, and lack of neurotrophic support are involved in copper-induced cognitive dysfunction. In addition, recent studies have found that copper mediates cuproptosis and adversely affects cognitive function. Cuproptosis is a copper-dependent, lipoylated mitochondrial protein-driven, non-apoptotic mode of regulated cell death, which provides us with new avenues for identifying and treating related diseases. However, the exact mechanism by which cuproptosis induces cognitive decline is still unclear, and this has attracted the interest of many researchers. In this paper, we analyzed the pathological mechanisms and therapeutic targets of copper-associated cognitive decline, mainly in the context of neurodegenerative diseases, psychiatric and psychological disorders, and diabetes mellitus.

Study on the Collection Efficiency of Bioaerosol Nanoparticles by Andersen-Type Impactors.

Airborne transmission is much more common than previously thought. Based on our knowledge about SARS-COV-2 (COVID-19) infection, the aerosol transmission routes for all respiratory infections must be reassessed. Thus far, the COVID-19 outbreak has caused catastrophic public health and economic crises, posing a serious threat to the lives and health of people around the world and directing public attention toward the airborne transmission of pathogens. The novel coronavirus transmission in the form of nanoaerosols in a wider range hinders prevention and early warning efforts. As a classical bioaerosol sampler, the Andersen six-stage sampler is widely used in the collection and research of aerosol particles. In this study, the physical and biological collection efficiency of the six-stage sampler was explored by qPCR and colony counting method. Results showed that the physical collection efficiency reached more than 50% when the particle size was larger than 0.75 µm. However, the overall biological collection efficiency was only 0.25%. In addition, fluorescence microscopy and flow cytometry were used to detect the microbial state after sampling, and the results showed that the proportion of the collected live bacteria was less than 15% of the total. This result is of great significance not only for the application of the Andersen six-stage sampler in collecting nanosized bioaerosols, but also provides reference for the selection of subsequent detection technologies for effective collection.

Tunable Si Dangling Bond Pathway Induced Forming-Free Hydrogenated Silicon Carbide Resistive Switching Memory Device.

With the coming of the big data age, the resistive switching memory (RSM) of three-dimensional (3D) high density shows a significant application in information storage and processing due to its simple structure and size-scalable characteristic. However, an electrical initialization process makes the peripheral circuits of 3D integration too complicated to be realized. Here a new forming-free SiCx:H-based device can be obtained by tuning the Si dangling bond conductive channel. It is discovered that the forming-free behavior can be ascribed to the Si dangling bonds in the as-deposited SiCx:H films. By tuning the number of Si dangling bonds, the forming-free SiCx:H RSM exhibits a tunable memory window. The fracture and connection of the Si dangling bond conduction pathway induces the switching from the high-resistance state (HRS) to the low-resistance state (LRS). Our discovery of forming-free SiCx:H resistive switching memory with tunable pathway opens a way to the realization of 3D high-density memory.

The Value of Corpus Callosum Measurement in the Diagnosis of Cerebral Atrophy.

OBJECTIVE: The study aimed to investigate the relationship between the corpus callosum area (CCa) and the degree of cerebral atrophy in patients with cerebral atrophy. METHODS: 119 patients with brain atrophy were grouped according to the degree of brain atrophy. Median sagittal CCa and intracranial area (ICa) were measured, and the ratio of corpus callosum to the intracranial area (CCa-ICa ratio) was calculated. The data were analyzed using ANOVA. RESULTS: CCa significantly reduced in patients with cerebral atrophy, and the degree of cerebral atrophy was found to be positively correlated with the degree of reduction in the CCa. CONCLUSION: The reduction in the CCa and the CCa-ICa ratio in the median sagittal can be used as a reference indicator for the diagnosis and grading of brain atrophy in clinical practice.

Hybrid channel induced forming-free performance in nanocrystalline-Si:H/a-SiNx:H resistive switching memory.

The unique forming-free feature of Si-based resistive switching memory plays a key role in the industrialization of next generation memory in the nanoscale. Here we report on a new forming-free nanocrystalline-Si:H (nc-Si:H)/SiNx:H resistive switching memory that can be obtained by deposition of hydrogen diluted nc-Si on hydrogen plasma treated a-SiNx:H layer. It is found that nc-Si dots with areal density of 5.6 × 1012/cm2 exist in nc-Si:H sublayer. Si dangling bonds (DBs) of volume density of 4.13 × 1023 cm-3 are produced in the a-SiNx:H sublayer. Temperature dependent current characteristic and theoretical calculations further reveal that hybrid channel of nc-Si and Si dangling bonds are the origin of the forming-free performance of nc-Si:H/SiNx:H resistive switching memory, which obey the trap assisted tunneling model at the low resistance state and P-F model at the high resistance state. Our discovery of hybrid channel supplies a new way to make Si-based RRAM be used in high density memory in the future.

Presetting conductive pathway induced the switching uniformity evolution of a-SiNx:H resistive switching memory.

Si-based resistive random access memory (RRAM) devices at the nanoscale with high uniformity have great potential applications in the future. We demonstrate that the uniformity evolution of the a-SiNx:H RRAM at the low resistance state (LRS) and the high resistance state (HRS) can be clearly monitored by presetting a Si dangling bond (Si-DB) conductive pathway through thermal energy. It is found that the increased magnitude of uniformity for the LRS and the HRS are determined by the number of preset Si-DBs, which can be controlled by tuning thermal energy. As for LRS, the Si-DBs produced under the electric field along with the preset Si-DB conductive pathways form the main conductive pathway. Theoretical calculation of current-voltage (I-V) curves indicates that the Si-DB conductive pathways obey the trap-assisted tunneling model. In the HRS, the preset Si-DBs induced by thermal energy are the unique source of the conductive pathway. The transmission mechanism involves a trap-to-trap process by the hopping of electrons under a low electric field, Poole-Frenkel emission in the main region under the medium electric field and Fowler-Nordheim tunneling under the high electric field. Our discovery of the uniformity evolution for a-SiNx:H RRAM device through presetting the Si-DB conductive pathway provides new insight into the resistive switching mechanism of next generation Si-based RRAM devices.

Colorimetric detection of low dose gamma radiation based on the aggregation of gold nanoparticles and its application for the blood irradiation.

To develop a simple and sensitive sensor for gamma radiation is of great importance not only for public safety, but also for rational utilization of ionizing radiation. In this study, a simple and sensitive method for colorimetric detection of low dose gamma radiation has been developed based on the single-strand DNA modified AuNPs (ssDNA-AuNPs), which were synthesized by immobilizing the sulfhydryl ssDNA on the surface of AuNPs. After the gamma radiation, the colors of ssDNA-AuNPs changed from wine-red to blue-purple gradually, and this can be easily distinguished by the naked eyes. Over a range from 0 to 30 Gy, a good linear relationship between the ratio of absorbance at 625 nm to that at 521 nm (A625/A521) in the UV-vis spectrum and radiation dose was obtained. The detection limit was as low as 0.5 Gy. The colorimetric mechanism was ascribed to the generation of hydroxyl radical during the gamma radiation. As a result, ssDNA was cut off and released from the AuNPs. Then the salt effect caused the aggregation leading to the distinct color change. The capability of the method has also been demonstrated for anti-radiation efficiency comparison of different radioprotectors. In addition, lymphocytes irradiation expriment indicated that the ssDNA-AuNPs prepared in this work can be successfully used for an indicator during blood irradiation to avoid transfusion associated graft vs. host disease (TA-GVHD).

Forming-free performance of a-SiN x :H-based resistive switching memory obtained by oxygen plasma treatment.

An a-SiN x -based resistive random access memory (RRAM) device with a forming-free characteristic has significant potentials for the industrialization of the next-generation memories. We demonstrate that a forming-free a-SiN x O y RRAM device can be achieved by an oxygen plasma treatment of ultra-thin a-SiN x :H films. Electron spin resonance spectroscopy reveals that Si dangling bonds with a high density (1019 cm-3) are distributed in the initial state, which exist in the forms of Si2N≡Si·, SiO2≡Si·, O3≡Si·, and N3≡Si·. X-ray photoelectron spectroscopy and temperature-dependent current analyses reveal that the silicon dangling bonds induced by the oxygen plasma treatment and external electric field contribute to the low resistance state (LRS). For the high resistance state (HRS), the rupture of the silicon dangling bond pathway is attributed to the partial passivation of Si dangling bonds by H+ and O2-. Both LRS and HRS transmissions obey the hopping conduction model. The proposed oxygen plasma treatment, introduced to generate a high density of Si dangling bonds in the SiN x O y :H films, provides a new approach to forming-free RRAM devices.

Spinal Epidural Cavernous Hemangioma: A Clinical Series of 7 Patients.

OBJECTIVE: To investigate imaging characteristics of spinal epidural cavernous hemangiomas (ECHs) and improve understanding of this rare disease. METHODS: This retrospective study included 7 cases of ECH, confirmed with surgical pathology and imaging. All patients underwent computed tomography and conventional magnetic resonance imaging. One patient underwent diffusion-weighted imaging. RESULTS: ECH originated from vertebrae with coarsened trabeculae in 5 patients. Among these, 1 tumor was mainly in the intervertebral foramen and paravertebral space, 2 extended to the intraspinal and paravertebral spaces and appeared dumbbell-shaped, and 2 were located in the intraspinal space. Purely epidural hemangiomas were present in 2 patients; 1 of these patients had adjacent bony erosion. Epidural hemangiomas were isointense in 6 patients and hyperintense in 1 patient on T1-weighted images; lesions were hyperintense on T2-weighted images in all 7 patients. Peripheral fat was present in 4 ECHs; 2 were of vertebral origin, and 2 were of epidural space origin. In the patient who underwent diffusion-weighted imaging, the lesion showed restricted diffusion. The affected vertebra had coarsened trabeculae, which may be a critical finding for differentiating ECHs of vertebral origin from foraminal nerve sheath tumors. Peripheral fat around hemangiomas of vertebral origin and primary epidural space hemangiomas indicates chronicity. CONCLUSIONS: ECHs are classified either as epidural hemangiomas of vertebral origin or as primary epidural hemangiomas. Awareness of imaging characteristics of ECHs may facilitate diagnosis and treatment of these lesions.

Initial experience of anti-PD1 therapy with nivolumab in advanced hepatocellular carcinoma.

PURPOSE: To evaluate efficacy and safety of anti-PD1 therapy with nivolumab for treatment of advanced hepatocellular carcinoma (HCC). METHODS: From Jan 2016 to Jan 2017, eleven cases of HCC (average age of 51.8-year), 4 at stage B and 7 at stage C, according to Barcelona Clinic Liver Cancer staging, were treated with nivolumab. There were 4 patients with lung metastasis, 1 with portal vein tumor thrombus, 1 with abdominal metastasis and 1 with bone metastasis. The protocol was nivolumab, 3 mg/kg, on day 1, q3w. All patients were treated for more than 4 cycles. During anti-PD1 treatment period, 6 patients also received sorafenib and 1 patient received cytokine-induced killer cell therapy. Objective response and clinical adverse events were evaluated retrospectively. RESULTS: Patients underwent a total of 80 cycles of nivolumab therapy, ranging between 4 and 18 cycles per patient. Nivolumab was associated with a disease control rate of 81.8%, with an objective response of 63.6% (Modified Response Evaluation Criteria in Solid Tumors). No adverse effects related to nivolumab were noted. CONCLUSION: Our experience shows that nivolumab could achieve acceptable outcome in HCC patients and may serve as an optional treatment, especially for patients who failed to gain a benefit from routine treatments.

Quantitative assessment of the degree of differentiation in colon cancer with dual-energy spectral CT.

OBJECTIVE: To evaluate dual-energy spectral CT imaging in evaluating the degree of differentiation in colon cancer. METHODS: Forty-seven colon cancer patients underwent spectral CT during arterial phase (AP) and portal venous phase (PP), and were characterized pathologically differentiated to well-differentiated (A, n = 18) and poorly differentiated or undifferentiated carcinoma group (B, n = 29). Lesion iodine concentration (IC) was measured and normalized to that of aorta (NIC). CT numbers were measured and the slope (λ HU) of the spectral HU curve was calculated. These parameters were statistically compared between the two groups. ROC curves were used to evaluate their diagnostic efficacies. RESULTS: There were significant differences in IC (1.01 ± 0.20 vs. 1.59 ± 0.57 mg/ml), NIC (0.12 ± 0.03 vs. 0.19 ± 0.09), λ HU (1.41 ± 0.29 vs. 2.03 ± 0.85), and CT number at 70 keV (48.61 ± 9.03HU vs. 63.97 ± 15.86HU) between groups A and B in AP (p < 0.05), but no difference in PP. Using IC = 1.13 mg/ml in AP as the threshold, one obtained a sensitivity of 81.8% and a specificity of 71.4% for differentiating well-differentiated from poorly differentiated or undifferentiated carcinoma. These values were statistically higher than those (64.7% and 62.3%) using CT number at 70 keV. CONCLUSION: Spectral CT imaging parameters (IC, NIC, and λ HU) in AP provide improved accuracy for evaluating the degrees of differentiation in colon cancer than CT number at 70 keV.

A dual-functional lanthanide nanoprobe for both living cell imaging and ICP-MS quantification of active protease.

Real-time imaging and quantitative monitoring of dynamic changes in biomolecules in bioprocesses is in urgent need for biological and clinical studies. However, this goal is difficult to achieve due to the incompatibility between the commonly used imaging and quantification methods. To fulfill this need, we developed the first nanoprobe capable of both living cell imaging and ultrasensitive quantification of proteases in cancer cells by taking advantage of the characteristic luminescence and ICP-MS response of lanthanide metals. The nanoprobe is composed of a lanthanide metal-based luminescent donor/mass tag and a gold nanoparticle quencher linked by a specific peptide recognized by proteases. The protease activity in living cells is both visualized and quantified by monitoring the enzymatically released lanthanide metal using fluorescence imaging and ICP-MS. The low ppb level sensitivity of this method demonstrates its potential in the study of protease-dependent pathways and related diseases.

a-SiNx:H-based ultra-low power resistive random access memory with tunable Si dangling bond conduction paths.

The realization of ultra-low power Si-based resistive switching memory technology will be a milestone in the development of next generation non-volatile memory. Here we show that a high performance and ultra-low power resistive random access memory (RRAM) based on an Al/a-SiNx:H/p(+)-Si structure can be achieved by tuning the Si dangling bond conduction paths. We reveal the intrinsic relationship between the Si dangling bonds and the N/Si ratio x for the a-SiNx:H films, which ensures that the programming current can be reduced to less than 1 µA by increasing the value of x. Theoretically calculated current-voltage (I-V) curves combined with the temperature dependence of the I-V characteristics confirm that, for the low-resistance state (LRS), the Si dangling bond conduction paths obey the trap-assisted tunneling model. In the high-resistance state (HRS), conduction is dominated by either hopping or Poole-Frenkel (P-F) processes. Our introduction of hydrogen in the a-SiNx:H layer provides a new way to control the Si dangling bond conduction paths, and thus opens up a research field for ultra-low power Si-based RRAM.

Carcinosarcoma of parotid gland (malignant mixed tumor).

Salivary gland carcinosarcoma is a rare neoplasm; with a poor prognosis. The most common epithelial components are adenocarcinoma or squamous cell carcinoma, whereas the most common mesenchymal components are chondrosarcoma. It should not be confused with the most common carcinoma ex-pleomorphic adenoma, in which the epithelial component alone is malignant. This condition might exhibit with a wide variety of presentation and symptoms along with associated conditions. We present a case of an old patient who presented with a very unusual type clinically with confusing presentation which was eventually diagnosed as carsinosarcoma. In addition, the literature is reviewed, and the possible clinical signs and management of malignant mixed tumor of the salivary gland are briefly discussed.

Hexagonal Ag nanoarrays induced enhancement of blue light emission from amorphous oxidized silicon nitride via localized surface plasmon coupling.

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays.

Poly(m-phenylenediamine)-based fluorescent nanoprobe for ultrasensitive detection of matrix metalloproteinase 2.

A novel fluorescence nanoprobe for the detection of matrix metalloproteinase 2 (MMP2) has been developed by engineering the fluorescein isothiocyanate-labeled peptide onto the surface of poly(m-phenylenediamine) (PMPD) nanoparticles through covalent linkage. The nanoprobe itself displays a low background signal due to the effective fluorescence quenching by electron-rich PMPD, but its reaction with MMP2 causes 11-fold fluorescence enhancement. Compared with similar fluorescence nanosystems for MMP2 assembled through physical adsorption, the as-prepared nanoprobe is significantly more stable and displays a strikingly higher signal-to-background ratio, which leads to a high sensitivity for MMP2 assay, with a detection limit of 32 pM. Most notably, the nanoprobe has been successfully applied to determine MMP2 in human serum samples, demonstrating that the MMP2 level in serum from colorectal cancer (CRC) patients is 2 times higher than that from healthy people. Moreover, the nanoprobe has also been used to monitor MMP2 secreted by CRC cells that were grown under normoxic and hypoxic conditions, respectively, and the results show that the cells under hypoxic conditions produce higher level of MMP2 than those under normoxic conditions. Our method is simple and can offer a highly sensitive detection of MMP2 in relevant clinical samples.

Preparation of mixed lanthanides-immobilized magnetic nanoparticles for selective enrichment and identification of phosphopeptides by MS.

A new type of mixed lanthanides-immobilized (Tb(3+) , Tm(3+) , Ho(3+) , Lu(3+) ) magnetic nanoparticles, Fe3 O4 @TCPP-DOTA-M(3+) , was prepared with a particle size of approximately 30 nm. A model protein, α-casein, and a protein mixture of α-casein and BSA (1:100) were first used to test the phosphopeptide enrichment efficiency of the newly developed magnetic nanoparticles. For the model protein α-casein, 19 phosphopeptides were identified with the newly developed materials. Even in the tryptic digest of α-casein and BSA (1:100), 16 phosphopeptides were easily detected, suggesting that the novel materials possess high selectivity in phosphopeptide enrichment. To evaluate the phosphopeptide enrichment efficiency in a real biological sample, the materials were used to capture phosphopeptides in the tryptic digests of an extract of HeLa cells. In total, 9048 phosphopeptides corresponding to 2103 phosphoproteins were identified in a single mass spectrometric analysis, indicating the great potential of the new materials for practical applications. Compared with metal oxide-based enrichment methods, the newly developed materials are convenient to prepare and easy to handle, and they save time in the phosphopeptide enrichment procedure, making these materials a good choice for highly selective and sensitive phosphopeptide enrichment in future phosphoproteome analyses.

Parallel comparative studies on the toxic effects of unmodified CdTe quantum dots, gold nanoparticles, and carbon nanodots on live cells as well as green gram sprouts.

By using confocal fluorescence microscopy and direct visualization, a parallel comparative investigation has been systematically made on the relative toxicity of three common nanomaterials, such as unmodified CdTe quantum dots (QDs), Au nanoparticles (Au NPs) and carbon nanodots (C-dots), to live cells as well as green gram sprouts. Bare CdTe QDs exert the most toxic effect on a variety of cell lines (HeLa, MCF-7, NIH/3T3 cells) as well as live plants (green gram sprouts). For cells, this toxic effect leads to the partial death of cells, the decrease of cell metabolic activity, the shrinkage of cells, the breakage of chromatin, the damage of cell membrane integrity, and the fragmentation of mitochondria; for green gram sprouts, the presence of CdTe QDs markedly inhibits their growth. Moreover, the toxic behaviors of CdTe QDs are dose- and time-dependent. Under the same conditions, Au NPs only decrease the metabolic activity of cells to a small extent, and do not affect the appearance of cellular/subcellular structures and the plant growth; interestingly, C-dots exert no obvious toxicity to both live cells and the growth of green gram sprouts, showing good biocompatibility. These parallel comparative studies clearly reveal that the relative toxicity of the three nanomaterials in their native forms is bare CdTe QDs>>Au NPs>C-dots, whose IC50 values for normal NIH/3T3 cells are 0.98 µg/mL, 62 µg/mL, and >250 µg/mL, respectively. This quantitative information is of great importance for right choice of the nanomaterials in their practical applications.