Monoaxial Screws Versus Polyaxial Screws Osteosynthesis for Unstable Atlas Fractures: A Retrospective, Comparative Study With a Minimum Follow-Up of 3 years.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The study aimed to compare the radiological parameters, clinical outcomes, and long-term effects of the posterior osteosynthesis with polyaxial screw-rod system and the monoaxial screw-rod system in the treatment of unstable atlas fractures. METHODS: We retrospectively analyzed the clinical data of 33 patients with posterior ORIF for unstable atlas fractures in our hospital from August 2013 to June 2020, with a minimum of 3 years of follow-up. Polyaxial screws (group A) were used in 12 patients and monoaxial screws (group B) in 21 patients. Perioperative data, radiological parameters, and clinical outcomes were collected and compared between the 2 surgical approaches. RESULTS: The operative time, blood loss, time of screw-rod system placement, and hospital stay were significantly lower in group A than in group B. At the last follow-up, the visual analog scale (VAS) score and anterior arch reduction rate of the atlas in group A were lower than those in group B, while the lateral mass displacement (LMD) in group A was higher than that in group B. There was no significant difference between Group A and Group B in terms of the anterior atlantodental interval (AADI), posterior arch reduction rate of the atlas, range of motion (ROM), and neck disability index (NDI). CONCLUSIONS: Monoaxial screws can achieve better reduction results for unstable atlas fractures, especially for the anterior arch of atlas. However, the surgical operation of monoaxial screws is more complicated than that of polyaxial screws and has more complications. Appropriate implants should be selected for the treatment of unstable atlas fractures based on the type of atlas fracture, the experience of surgeons, and the demands of patients.

Design of a novel lateral mass screw-plate system for the treatment of unstable atlas fractures: a finite element analysis.

BACKGROUND: Osteosynthesis of unstable atlas fractures preserves joint motion and therefore has a distinct advantage over a range of treatment procedures. To prevent the potential disadvantages associated with osteosynthesis, a new atlas lateral mass screw-plate (LMSP) system has been designed. However, the biomechanical role of using the LMSP system in atlas internal fixation is not known. The aim of this study was to compare the biomechanical stability of a new LMSP with traditional posterior screw and rod (PSR) fixation techniques on the occipitocervical junction (C0-C2) through finite element analysis. METHODS: A nonlinear C0-C2 finite element model of the intact upper cervical spine was developed and validated. The unstable model using the PSR system was then compared with the model using the LMSP system for fixation. A vertical load of 40 N was applied to the C0 to simulate head weight, while a torque of 1.5 Nm was applied to the C0 to simulate flexion, extension, lateral bending, and axial rotation. RESULTS: The range of motion of both systems was close to the intact model. Compared with the LMSP system model, the PSR system model increased flexion, extension, lateral bending, and axial rotation by 4.9%, 3.0%, 5.0%, and 29.5% in the C0-C1 segments, and 4.9%, 2.7%, 2.4%, and 22.6% in the C1-C2, respectively. In flexion, extension, and lateral bending motion, the LMSP system model exhibited similar stress to the PSR system model, while in axial rotation, the PSR system model exhibited higher stress. CONCLUSIONS: The findings of our study indicate that the two tested system models provide comparable stability. However, better stability was achieved during axial rotation with the LMSP system, and in this system, the maximum von Mises stress was less than that of the PSR one. As the atlantoaxial joint functions primarily as a rotational joint, the use of the LMSP system may provide a more stable environment for the joint that has become unstable due to fracture.

Direct osteosynthesis in the treatment of atlas burst fractures: a systematic review.

PURPOSE: The treatment of unstable atlas fractures remains a controversial topic. The study aims at assessing the prognosis and efficacy of osteosynthesis for unstable atlas fractures through a review of the current literature and additionally aims to compare outcomes between the transoral and posterior approaches. METHODS: A systematic review of databases including PubMed, EMBASE, Cochrane, Web of Science, CNKI, and Wanfang was conducted. Titles and abstracts were screened by two reviewers to identify studies meeting pre-defined inclusion criteria for comprehensive analysis. RESULTS: The systematic review included 28 articles, 19 employing the posterior approach and 9 utilizing the transoral approach. It covered osteosynthesis in 297 patients with unstable atlas fractures, comprising 169 treated via the posterior approach and 128 via the transoral approach. Analysis revealed high healing rates and clinical improvement in both approaches, evidenced by improvements in the visual analog scale, range of motion, atlantodens interval, and lateral displacement distance post-surgery. CONCLUSION: Osteosynthesis offers effective treatment for unstable atlas fractures. Both transoral and posterior approaches can achieve good clinical outcomes for fracture, and biomechanical studies have confirmed that osteosynthesis can maintain the stability of the occipitocervical region, preserve the motor function of the atlantoaxial and occipito-atlantoaxial joints, and greatly improve the quality of life of patients. However, variations exist in the indications and surgical risks associated with each method, necessitating their selection based on a thorough clinical evaluation of the patient's condition.

C1 anatomy and dimensions relative to pedicle screw placement.

The recent C1 pedicle screw technique for upper cervical vertebral stabilization allows longer screws to be implanted by setting the screw entry point through the posterior arch of C1, which could provide better biomechanics. However, there is controversy regarding the placement of C1 pedicle screws at different angles. We retrospectively reviewed the computed tomography (CT) scans of 300 patients. The trajectories of medial inclination of 0°, 5°, 10°, and 15° and trajectory of the maximum medial inclination angle were designed for each C1 pedicle on CT images. Screw track length at each angle, the angle of maximum medial inclination, pedicle height, distance from the screw entry point to the midpoint of the C1 posterior tubercle, and screw perforation rate at each angle were measured. The average maximum inclination angle was 17.01°, the maximum inclination angle screw track length was 31.05 mm, and the distance from the screw entry point to the midpoint of the C1 posterior nodule was 21.65 mm. The screw perforation rate was 46.73% at 15° of medial inclination, but only 5.61% at 10°, and no screw perforation at 5°. 26.47% C1 pedicle height < 4 mm. There was no significant difference between the measured data on the left and right sides(P > 0.05), and the measurement of female patients was usually smaller and significantly different from that of male patients(p < 0.05). Our data indicate that a reasonable screw inclination angle of 10° and the safety zone of screw angle can provide safety and avoid screw perforation. However, personalized measurement before surgery is essential.

Posterior osteosynthesis with a new self-designed lateral mass screw-plate system for unstable atlas burst fractures.

BACKGROUND: In the treatment of unstable atlas fractures using the combined anterior-posterior approach or the posterior monoaxial screw-rod system, factors such as severe trauma or complex surgical procedures still need to be improved despite the favourable reduction effect. This research described and evaluated a new technique for the treatment of unstable atlas fracture using a self-designed lateral mass screw-plate system. METHODS: A total of 10 patients with unstable atlas fractures using this new screw-plate system from January 2019 to December 2021 were retrospectively reviewed. All patients underwent posterior open reduction and internal fixation (ORIF) with a self-designed screw-plate system. The medical records and radiographs before and after surgery were noted. Preoperative and postoperative CT scans were used to determine the type of fracture and evaluate the reduction of fracture. RESULTS: All 10 patients were successfully operated with this new system, with an average follow-up of 16.7 ± 9.6 months. A total of 10 plates were placed, and all 20 screws were inserted into the atlas lateral masses. The mean operating time was 108.7 ± 20.1 min and the average estimated blood loss was 98.0 ± 41.3 ml. The lateral mass displacement (LMD) averaged 7.1 ± 1.9 mm before surgery and almost achieved satisfactory reduction after surgery. All the fractures achieved bony healing without reduction loss or implant failure. No complications (vertebral artery injury, neurologic deficit, or wound infection) occurred in these 10 patients. At the final follow-up, the anterior atlantodens interval (AADI) was 2.3 ± 0.8 mm and the visual analog scale (VAS) was 0.6 ± 0.7 on average. All patients preserved almost full range of motion of the upper cervical spine and achieved a good clinical outcome at the last follow-up. CONCLUSIONS: Posterior osteosynthesis with this new screw-plate system can provide a new therapeutic strategy for unstable atlas fractures with simple and almost satisfactory reduction.

[Clinical application of special fluoroscopy method in the treatment of distal radius fractures with volar locking plate].

OBJECTIVE: The relationship between the distal screws and the wrist articular surface was assessed by the additional lateral oblique fluoroscopic view during the operation, and the dorsal tangential view of the wrist was used to observe whether the distal screw penetrated the dorsal cortex, so as to evaluate the clinical efficacy of the volar locking plate in the treatment of distal radius fractures. METHODS: From January 2020 to June 2021, 45 cases of fresh distal radius fractures were treated using the volar Henry's approach, including 20 males and 25 females, aged from 32 to 75 years old with an average of (52.4±8.1) years old. During the operation, they were divided into 2 groups according to the different intraoperative fluoroscopic views:the control group of 20 cases, treated with standard anteroposterior and lateral fluoroscopic view;25 cases in the observation group, additional lateral oblique fluoroscopic view and dorsal tangential view of the wrist were taken. The wrist joint function score and postoperative complications were evaluated at 6 weeks, 3 and 6 months after operation between two groups. RESULTS: All 45 patients were followed up and the duration ranged from 6 to 14 months, with an average of (10.8±1.7) months, all patients achieved bone union and the incision healed well. The incidence of postoperative complications in the observation group was lower than that in the control group, and the difference was statistically significant (P<0.05). In terms of Gartland-Werley score of wrist joint function, the score of wrist function in the observation group was (4.58±1.31) at 6 weeks, (2.98±0.63) at 3 months and (1.95±0.65) at 6 months post-operatively, which were better than those in the control group (6.32±1.96) at 6 weeks, (3.63±0.76) at 3 months and (2.43±0.73) at 6 months. The difference was statistically significant (P<0.05). In the observation group, 7/25 cases(28%) were found to have screw penetration during the operation by additional lateral oblique and dorsal tangential radiograph fluoroscopic views of wrist. CONCLUSION: The addition of lateral oblique and dorsal tangential during the operation could improve the accuracy of distal screw placement, reduce postoperative complications, and achieve early functional exercise.

Robot-Assisted Percutaneous Lag Screw Osteosynthesis for C1 Lateral Mass Fractures: Case Series and Technical Note.

BACKGROUND: C1 lateral mass fractures (LMF) cause abnormal alignment of the upper cervical joints. Conservatively treated cases can develop into late cock-robin junction, requiring a reconstructive surgical procedure of the occipitocervical junction. Partial coronal C1 LMF could be effectively fixed with lag screws. Navigation and robot-assisted techniques have made percutaneous fixation possible and are gradually being used in the upper cervical spine. METHODS: Five consecutive patients with C1 LMF who underwent percutaneous lag screw osteosynthesis under the guidance of a new robotic system were reviewed retrospectively. Preoperative and postoperative computed tomography scans were used to specify the fracture types and to assess the efficacy of fracture reduction. The medical records were reviewed. RESULTS: Among the 5 patients, 4 underwent percutaneous lag screw reduction and fixation with the assistance of the robotic system through a posterior approach and 1 patient underwent a transoral approach. No intraoperative complications, such as screw malposition, neurologic deficit, and vertebral artery injury, occurred. Satisfactory fracture reduction and bone healing were achieved at postoperative follow-up. CONCLUSIONS: Robot-assisted percutaneous lag screw osteosynthesis is a viable option for C1 LMF. Different approaches can be selected according to the distribution of the fracture lines. With the posterior approach, the guidewire tends to deviate from the entry point because of skiving, and the technical problems need to be further solved. Screw implant by a transoral approach is comparatively easy to achieve, but the possibly of infection exists and should be monitored.

Novel invagination procedure for pancreaticojejunostomy using double purse string sutures: A technical note.

BACKGROUND: Postoperative pancreatic fistula (POPF) is one of the most serious complications after pancreaticoduodenectomy (PD), and the choice of pancreaticojejunostomy (PJ) is considered a key factor affecting the occurrence of POPF. Numerous anastomotic methods and their modifications have been proposed, and there is no method that can completely avoid the occurrence of POPF. Based on our team's experience in pancreatic surgery and a review of relevant literature, we describe a novel invagination procedure for PJ using double purse string sutures, which has resulted in favourable outcomes. AIM: To describe the precise procedural steps, technical details and clinical efficacy of the novel invagination procedure for PJ. METHODS: This study adopted a single-arm retrospective cohort study methodology, involving a total of 65 consecutive patients who underwent PD with the novel invagination procedure for PJ, including the placement of a pancreatic stent, closure of the residual pancreatic end, and two layers of purse-string suturing. Baseline data included age, sex, body mass index (BMI), pancreatic texture, pancreatic duct diameter, operation time, and blood loss. Clinical outcomes included the operation time, blood loss, and incidence of POPF, postoperative haemorrhage, delayed gastric emptying, postoperative pulmonary infection, postoperative abdominal infection, and postoperative pulmonary infection. RESULTS: The mean age of the patients was 59.12 (± 8.08) years. Forty males and 25 females were included, and the mean BMI was 21.61 kg/m2 (± 2.74). A total of 41.53% of patients had a pancreatic duct diameter of 3 mm or less. The mean operation time was 263.83 min (± 59.46), and the mean blood loss volume was 318.4 mL (± 163.50). Following the surgical intervention, only three patients showed grade B POPF (4.62%), while no patients showed grade C POPF. Five patients (5/65, 7.69%) were diagnosed with postoperative haemorrhage. Six patients (6/65, 9.23%) experienced delayed gastric emptying. Four patients (4/65, 6.15%) developed postoperative pulmonary infection, while an equivalent number (4/65, 6.15%) exhibited postoperative abdominal infection. Additionally, two patients (2/65, 3.08%) experienced postoperative pulmonary infection. CONCLUSION: The novel invagination technique for PJ is straightforward, yields significant outcomes, and has proven to be safe and feasible for clinical application.

Nanostructured and Advanced Designs from Biomass and Mineral Residues: Multifunctional Biopolymer Hydrogels and Hybrid Films Reinforced with Exfoliated Mica Nanosheets.

Transforming potential waste materials into high-value-added sustainable materials with advanced properties is one of the key targets of the emerging green circular economy. Natural mica (muscovite) is abundant in the mining industry, which is commonly regarded as a byproduct and gangue mineral flowing to waste rock and mine tailings. Similarly, chitin is the second-most abundant biomass resource on Earth after cellulose, extracted as a byproduct from the exoskeleton of crustaceans, fungal mycelia, and mushroom wastes. In this study, exfoliated mica nanosheets were individualized using a mechanochemical process and incorporated into regenerated chitin matrix through an alkali dissolution system (KOH/urea) to result in a multifunctional, hybrid hydrogel, and film design. The hydrogels displayed a hierarchical and open nanoporous structure comprising an enhanced, load-bearing double-cross-linked polymeric chitin network strengthened by mica nanosheets possessing high stiffness after high-temperature curing, while the hybrid films (HFs) exhibited favorable UV-shielding properties, optical transparency, and dielectric properties. These hybrid designs derived from industrial residues pave the way toward sustainable applications for many future purposes, such as wearable devices and tissue engineering/drug delivery.

Inhibition of Nav1.7 channel by a novel blocker QLS-81 for alleviation of neuropathic pain.

Voltage-gated sodium channel Nav1.7 robustly expressed in peripheral nociceptive neurons has been considered as a therapeutic target for chronic pain, but there is no selective Nav1.7 inhibitor available for therapy of chronic pain. Ralfinamide has shown anti-nociceptive activity in animal models of inflammatory and neuropathic pain and is currently under phase III clinical trial for neuropathic pain. Based on ralfinamide, a novel small molecule (S)-2-((3-(4-((2-fluorobenzyl) oxy) phenyl) propyl) amino) propanamide (QLS-81) was synthesized. Here, we report the electrophysiological and pharmacodynamic characterization of QLS-81 as a Nav1.7 channel inhibitor with promising anti-nociceptive activity. In whole-cell recordings of HEK293 cells stably expressing Nav1.7, QLS-81 (IC50 at 3.5 ± 1.5 µM) was ten-fold more potent than its parent compound ralfinamide (37.1 ± 2.9 µM) in inhibiting Nav1.7 current. QLS-81 inhibition on Nav1.7 current was use-dependent. Application of QLS-81 (10 µM) caused a hyperpolarizing shift of the fast and slow inactivation of Nav1.7 channel about 7.9 mV and 26.6 mV, respectively, and also slowed down the channel fast and slow inactivation recovery. In dissociated mouse DRG neurons, QLS-81 (10 µM) inhibited native Nav current and suppressed depolarizing current pulse-elicited neuronal firing. Administration of QLS-81 (2, 5, 10 mg· kg-1· d-1, i.p.) in mice for 10 days dose-dependently alleviated spinal nerve injury-induced neuropathic pain and formalin-induced inflammatory pain. In addition, QLS-81 (10 µM) did not significantly affect ECG in guinea pig heart ex vivo; and administration of QLS-81 (10, 20 mg/kg, i.p.) in mice had no significant effect on spontaneous locomotor activity. Taken together, our results demonstrate that QLS-81, as a novel Nav1.7 inhibitor, is efficacious on chronic pain in mice, and it may hold developmental potential for pain therapy.

Electrochemiluminescence immunoassay for the prostate-specific antigen by using a CdS/chitosan/g-C3N4 nanocomposite.

An electrochemiluminescence (ECL) biosensor was fabricated for the evaluation of prostate specific antigen (PSA). The sensor was developed by successively modifying glassy carbon electrode (GCE) electrodes with CdS/Chito/g-C3N4 nanocomposites and DNA1 was labeled at the 5' end with thiol. The aptamer DNA was labeled at the 3' end with a quencher ferrocene (Fc) was ligated to DNA1 by the principle of complementary base pairing. In the absence of PSA, the ECL intensity signal is effectively quenches through the energy transfer and photoexcitation electron transfer between CdS/Chito/g-C3N4 emitter and quencher Fc. After incubation with target PSA, the aptamer DNA interacts with PSA and then moved away from the electrode surface together, which will recover the ECL intensity. Under the optimal conditions, the ECL intensity increases linearly with the logarithm of PSA concentration in the range of 1 pg·mL-1 to 100 ng·mL-1, and the detection limit is 0.14 pg·mL-1 (S/N = 3). The biosensor has been successfully applied to the determination of PSA in serum sample. Graphical abstractSchematic representation of the electrochemiluminescence sensor based on a CdS/chitosan/g-C3N4 nanocomposite, which can be applied to the determination of prostate specific antigen in serum.

A separation-free and pizza-structure PAM/GCN/PAA composite hydrogel (PCH) in wastewater treatment at visible light or solar light.

During wastewater treatment, the separation of powder nano-photocatalyst from treated water is a limiting factor for the commercial application of the powder photocatalysts. In this study, a photocatalyst, i.e. graphitic carbon nitride (GCN) was immobilized in network of polyacrylic acid (PAA) hydrogel to solve this issue. To further immobilizing GCN and strengthening hydrogel, polyacrylamide (PAM) was introduced to form interpenetrating network with PAA. In this structure, PAM acted the role of cheese in a pizza, tightly covering and immobilizing GCN into the interpenetrating network. During the cyclic tests, PCH with 20 mg (PCH20) can be successively reused 5 times compared 3 times of GCN/PAA with the RhB photodegradation efficiency over 95% each time. Meanwhile, GCN retention rates of GCN/PAA and PCH20 are 71.2 ± 5.2% and 97.2 ± 1.9% respectively. Besides, GCN played initiator role in the polymerization of PAM. PCH20 was more stable comparing with GCN/PAA hydrogel at both mechanical and thermal characterization. Furthermore, PCH20 showed excellent photocatalysis capability to RhB dyed wastewater at both visible and solar light. During 5 time's continuously cyclic tests, the photodegradation efficiency of PCH20 over RhB solution (10 mgL-1) was over 95% within 2 h under visible light (100 mWcm-2) each time. By changing pH values of solution from 3 to 9, the degree of swelling ratio (Dsw) of PCH20 could achieve from 307 ± 39% to 2361 ± 135%. PCH20 was feasible to obtain large surface area through swelling and it was beneficial for GCN to harvest the light. Hence, the photodegradation performance of PCH20 in RhB solution of pH 7, 9 was better than its in the original (pH 5.7) or the pH 3 RhB solution. The preparation of PCH20 was environmental friendly and cost-efficient without using any photoinitiators and crosslinking agents except GCN.

Electrochemiluminescent biosensor with DNA link for selective detection of human IgG based on steric hindrance.

A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

Synthesis of ultrathin WSe2 nanosheets and their high-performance catalysis for conversion of amines to imines.

Tungsten diselenide (WSe2) is the material with the lowest thermal conductivity in the world. Most physical methods are used for the synthesis of tungsten diselenide. Here, a simple colloidal method is reported for the synthesis of WSe2 nanosheets. The composition, valence, size, morphology and properties of the samples were characterized and measured. Results showed that the obtained WSe2 nanosheets with a thickness of 0.7 nm had strong blue fluorescence. Significantly, the synthesized WSe2 nanosheets exhibited excellent catalytic activity for the aerobic coupling of amines to imines, with 100% yield under visible light irradiation and air atmosphere. As a photocatalyst, it exhibited excellent recyclability, and maintained a high yield after 5 cycles. It was found that this reaction could also happen in the presence of natural light by slightly extending the reaction time. Moreover, H2O was used as a solvent in the catalytic process, avoiding expensive and toxic organic solvents. This work provides an efficient, economical and sustainable process for the synthesis of imines and shows the great potential of WSe2 nanosheets as photocatalysts for organic synthesis.

Enhanced photoelectrochemical DNA sensor based on TiO2/Au hybrid structure.

A novel enhanced photoelectrochemical DNA sensor, based on a TiO2/Au hybrid electrode structure, was developed to detect target DNA. The sensor was developed by successively modifying fluorine-tin oxide (FTO) electrodes with TiO2 nanoparticles, gold (Au) nanoparticles, hairpin DNA (DNA1), and CdSe-COOH quantum dots (QDs), which acted as signal amplification factors. In the absence of target DNA, the incubated DNA1 hairpin and the CdSe-COOH QDs were in close contact with the TiO2/Au electrode surface, leading to an enhanced photocurrent intensity due to the sensitization effect. After incubation of the modified electrode with the target DNA, the hairpin DNA changed into a double helix structure, and the CdSe QDs moved away from the TiO2/Au electrode surface, leading to a decreased sensitization effect and photoelectrochemical signal intensity. This novel DNA sensor exhibited stable, sensitive and reproducible detection of DNA from 0.1 µM to 10 fM, with a lower detection limit of 3 fM. It provided good specificity, reproducibility, stability and is a promising strategy for the detection of a variety of other DNA targets, for early clinical diagnosis of various diseases.

A label-free photoelectrochemical biosensor for urokinase-type plasminogen activator detection based on a g-C3N4/CdS nanocomposite.

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C3N4/CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C3N4/CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL-1, ranging from 1 µg mL-1-0.1 pg mL-1. The proposed strategy should provide a promising method for detection of other biomarkers.

Potential of secondary aerosol formation from Chinese gasoline engine exhaust.

Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds (VOCs). However, little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4-5hr simulation, which was estimated to represent more than 10days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol (SOA) production was 426±85mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.

Highly sensitive electrochemical biosensor for streptavidin detection based on CdSe quantum dots.

An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.

Colloidal Synthesis and Thermoelectric Properties of CuFeSe2 Nanocrystals.

Copper-based chalcogenides that contain abundant, low-cost and environmentally-friendly elements, are excellent materials for numerous energy conversion applications, such as photocatalysis, photovoltaics, photoelectricity and thermoelectrics (TE). Here, we present a high-yield and upscalable colloidal synthesis route for the production of monodisperse ternary I-III-VI2 chalcogenides nanocrystals (NCs), particularly stannite CuFeSe2, with uniform shape and narrow size distributions by using selenium powder as the anion precursor and CuCl2·2H2O and FeCl3 as the cationic precursors. The composition, the state of valence, size and morphology of the CuFeSe2 materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), respectively. Furthermore, the TE properties characterization of these dense nanomaterials compacted from monodisperse CuFeSe2 NCs by hot press at 623 K were preliminarily studied after ligand removal by means of hydrazine and hexane solution. The TE performances of the sintered CuFeSe2 pellets were characterized in the temperature range from room temperature to 653 K. Finally, the dimensionless TE figure of merit (ZT) of this Earth-abundant and intrinsic p-type CuFeSe2 NCs is significantly increased to 0.22 at 653 K in this work, which is demonstrated to show a promising TE materialand makes it a possible p-type candidate for medium-temperature TE applications.

Characterization of non-methane hydrocarbons and their sources in an industrialized coastal city, Yangtze River Delta, China.

Ningbo is a highly industrialized city in the coastal area of the Yangtze River Delta (YRD), China. Large emissions and transport of non-methane hydrocarbons (NMHCs) may contribute to regional ozone (O3) and particulate matter (PM) pollution; however, the concentrations and sources of ambient NMHCs have not yet been investigated in Ningbo. In this study, ambient NMHCs were measured at two residential (SZ and CX) and two industrial (ZH and BL) sites and one suburban (XS) site over ten consecutive days in each season (10-20 December 2012 in winter, 14-23 April 2013 in spring, 15-24 July 2013 in summer, 22-31 October 2013, in autumn). A positive matrix factorization (PMF) model using multiple site data was deployed to explore the source contributions and their spatial and seasonal characteristics. The measurement results showed obvious seasonal variations in ambient NMHC concentrations (ranging from 17.89-28.48ppbv); chemical compositions were similar among the five sampling sites. PMF analysis showed that the petrochemical industry was the largest contributor (an average of 35.64%) to ambient NMHCs, while contributions of smaller sources (i.e., chemical and paint industries [14.34%], fuel and tank evaporation [16.02%], and residential solvent usage [7.24%]) showed spatial variations. Liquefied petroleum gas and fuel and tank evaporation contributed more in summer and autumn, while the contribution of the chemical and paint industries was greater in spring and winter. An evaluation of the ozone formation potential and secondary organic aerosol potential suggested that petrochemical and solvent-related sources were key parameters in mitigation of secondary pollutant formation. Seasonal variations in source contributions should be considered when formulating an effective NMHC abatement strategy.