Synthesis and structural characterization of inverse-coordination clusters from a two-electron superatomic copper nanocluster

We have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu13{S2CNR2}6{C[triple bond, length as m-dash]CR'}4](PF6), 1a-d (where a: R = n Bu, R' = CO2Me; b: R = n Bu, R' = CO2Et; c: R = iPr, R' = CO2Et; d: R = n Pr, R' = 3,5-(CF3)2C6H3); [Cu12(μ12-S){S2CNR2}6{C[triple bond, length as m-dash]CR'}4], 2a-c; [Cu12(μ12-Cl){S2CNR2}6{C[triple bond, length as m-dash]CR'}4](PF6), 3a-e (where e: R = n Bu, R' = Ph); [Cu12(μ12-Br){S2CN n Bu2}6{C[triple bond, length as m-dash]CPh}4](PF6), 4e; and [Cu12(μ12-Cl)(μ3-Cl){S2CN n Bu2}6{C[triple bond, length as m-dash]CCO2Me}3]+ 5a. Cluster 1a is the first structurally characterized copper cluster having a Cu13 centered cuboctahedral arrangement, a miniature of the bulk copper fcc structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms 1 was confirmed by XANES. Inverse coordination clusters 2-5 are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu1-) in nanoclusters 1 can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters 2-5 which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br ≈ Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS, 1H, 13C NMR, IR, UV-visible, emission spectroscopy, and the structures 2a-b, 3d-e, 4e and 5a were established by X-ray diffraction analysis.

Role of Soluble ST2 Levels and Beta-Blockers Dosage on Cardiovascular Events of Patients with Unselected ST-Segment Elevation Myocardial Infarction

Background:

Serum soluble ST2 (sST2) levels are elevated early after acute myocardial infarction and are related to adverse left ventricular (LV) remodeling and cardiovascular outcomes in ST-segment elevation myocardial infarction (STEMI). Beta-blockers (BB) have been shown to improve LV remodeling and survival. However, the relationship between sST2, final therapeutic BB dose, and cardiovascular outcomes in STEMI patients remains unknown.

Methods:

A total of 186 STEMI patients were enrolled at the Wuhan Asia Heart Hospital between January 2015 and June 2015. All patients received standard treatment and were followed up for 1 year. Serum sST2 was measured at baseline. Patients were divided into four groups according to their baseline sST2 values (high >56 ng/ml vs. low ≤56 ng/ml) and final therapeutic BB dose (high ≥47.5 mg/d vs. low <47.5 mg/d). Cox regression analyses were performed to determine whether sST2 and BB were independent risk factors for cardiovascular events in STEMI.

Results:

Baseline sST2 levels were positively correlated with heart rate (r = 0.327, P = 0.002), Killip class (r = 0.408, P = 0.000), lg N-terminal prohormone B-type natriuretic peptide (r = 0.467, P = 0.000), lg troponin I (r = 0.331, P = 0.000), and lg C-reactive protein (r = 0.307, P = 0.000) and negatively correlated to systolic blood pressure (r = −0.243, P = 0.009) and LV ejection fraction (r = −0.402, P = 0.000). Patients with higher baseline sST2 concentrations who were not titrated to high-dose BB therapy (P < 0.0001) had worse outcomes. Baseline high sST2 (hazard ratio [HR]: 2.653; 95% confidence interval [CI]: 1.201–8.929; P = 0.041) and final low BB dosage (HR: 1.904; 95% CI, 1.084–3.053; P = 0.035) were independent predictors of cardiovascular events in STEMI.

Conclusions:

High baseline sST2 levels and final low BB dosage predicted cardiovascular events in STEMI. Hence, sST2 may be a useful biomarker in cardiac pathophysiology.

[Clinical application of Acutegastrointestinal injury grading system assocaited with clinical severity outcome in critically ill patients: a multi-center prospective, observational study]

Objective: To investigate the feasibility of utilizing the current acute gastrointestinal injury(AGI) grading system, and explore the association of severity of AGI grade with clinical outcome in critically ill patients. Methods: The adult patients from 14 general ICUs in Zhejiang Province with an expected admission to ICU for at least 24 h were recruited, and all clinical, laboratory, and survival data were prospectively collected. The AGI grade was daily assessed based on GIsymptoms, feeding details and organ dysfunctionon the first week of admission to ICU.The intra-abdominal pressures(IAP) was measured using AbViser device. Results: Of 550 patients enrolled, mean values for age and APACHE Ⅱ score were (64.9±17.2) years and (19.5±7.4), respectively. 456 patients(82.9%) took mechanical ventilation, and 470 patients were identified for AGI. The distribution of AGI grade on the frist day of ICU admission were 50.6%(Ⅰ grade, n=238), 34.2%(Ⅱ grade, n=161), 12.4%(Ⅲ grade, n=58) and 2.8%(Ⅳ, n=13), respectively, while the distribution of the global AGI grade based on the 7-day AGI assessment of ICU admission were 24.5%(Ⅰ grade, n=115), 49.4%(Ⅱ grade, n=232), 20.6%(Ⅲ grade, n=97) and 5.5%(Ⅳ, n=26), respectively. 28- and 60-day mortality rate was 29.3%(n=161) and 32.5%(n=179), respectively. The patients with AGI had a higher 28-(31.1% vs 18.8%, P=0.025) and 60-day survival rate(34.7% vs 20.0%, P=0.01) than those with non-AGI, and also there were positive correlations between AGI grade and 28- and 60-day mortality(P<0.001). Univariate Cox regression analysis showed that age, the source of medicial admission, diabetes mellitus, coronary heart disease, the use of vasoactive drugs, serum creatinine and lactate, mechanical ventilation, APACHE Ⅱ score, the AGI grade in the first day of ICU admission and feeding intolerance within the first week of ICU stay were significantly(P≤0.02) associated with mortality. In multivariate analysis including all these variables, the source of medical admission(χ(2)=4.34, P=0.04), diabete mellitus(χ(2)=3.96, P=0.05), the use of vasoactive drugs(χ(2)=6.55, P=0.01), serum lactate(χ(2)=4.73, P=0.03), the global AGI grade in the 7-day of ICU admission(χ(2)=7.10, P=0.008), and APACHE Ⅱ score(χ(2)=12.1, P<0.001) remained independent predictors for 60-day mortality.In the further subgroup analysis including 402 patients with 7-day survival, the feeding intolerance within the first week of ICU stay could provide independent and incremental prognostic value of 60-day mortality wtih increased χ(2)value of Cox regression model(χ(2)=52.2 vs 41.9, P=0.007) . Conclusion: The AGI grading system is useful for identifying the severity of gastrointestinal dysfunction, and could be used as a strong predictor of impaired outcome. The results provide evidence to support that feeding intolerance within 7 days of admission to ICU was an independent determinant of mortality.

Synthesis, structural characterization and transformation of an eight-electron superatomic alloy, [Au@Ag19{S2P(OPr)2}12]

Controlling the metal nanoclusters with atomic precision is highly difficult and further studies on their transformation reactions are even more challenging. Herein we report the controlled formation of a silver alloy nanocluster [AuAg19{S2P(OnPr)2}12] (1) from an Ag20 template via a galvanic exchange route. X-ray structural analysis reveals that the alloy structure comprises of a gold-centered Ag12 icosahedron, Au@Ag12, capped by seven silver atoms. Interestingly upon reacting with one equiv. of silver(i) salt, (1) can transform into a higher nuclearity nanocluster, [Au@Ag20{S2P(OnPr)2}12]+ (2). The conversion process is studied via ESI mass spectrometry and 31P NMR spectroscopy. This kind of size-structural transformation at the single atom level is quite remarkable. Furthermore, the compositions of all the doped nanoclusters (1, 2) were fully characterized with ESI-MS and EDS. The blue shift depicted in the UV-visible and emission spectra of the doped nanoclusters (1, 2) compared with the precursor, Ag20, demonstrates that the doping atoms have significant effects on the electronic structures.

[Strategies for the prevention and control of bleeding due to vascular injury in thoracoscopic lung surgery]

The technique of thoracoscopic lung surgery has gradually matured. Nowadays, thoracoscope is recommended as the most preferred approach for surgical treatment of early stage non-small cell lung cancer in different guidelines. However, there are still some cases of accidential major bleeding due to vascular injury during thoracoscopic lung surgery. The wall of the hilum vessels is relatively thin. These vessels often involve a great portion of the cardiac output blood flow. Once the injury happened, the emergent condition may be life-threatening due to massive blood loss. Therefore, this became an important factor which hindered the development of thoracoscopic lung surgery. In this review, details of the vascular injury in thoracoscopic lung surgery were summarized, including the incidence of vascular injury, commonly injured sites and reasons of the injuries. Among all the cases of thoracoscopic major pulmonary resection, 2.9% to 9.2% may suffer from vascular injury during the operation. The most commonly injuried sites are pulmonary artery and the branches, and this is also the most critical situation during thoracoscopic lung surgery. Hilum adhesion is the most important risk factor for vascular injury. On the one hand, the suction-compressing angiorrhaphy technique was developed for bleeding control and angioplasty. On the other hand, the strategies like pre-control of the pulmonary, cut the bronchus in advance, and fire the bronchus and pulmonary artery together may decrease the incidence of vascular injury in patients with risk factors.

Indication of band flattening at the Fermi level in a strongly correlated electron system

Using ultra-high quality SiGe/Si/SiGe quantum wells at millikelvin temperatures, we experimentally compare the energy-averaged effective mass, m, with that at the Fermi level, m_F, and verify that the behaviours of these measured values are qualitatively different. With decreasing electron density (or increasing interaction strength), the mass at the Fermi level monotonically increases in the entire range of electron densities, while the energy-averaged mass saturates at low densities. The qualitatively different behaviour reveals a precursor to the interaction-induced single-particle spectrum flattening at the Fermi level in this electron system.

SYNTAX Score of Infarct-Related Artery Other Than the Number of Coronary Balloon Inflations and Deflations as an Independent Predictor of Contrast-Induced Acute Kidney Injury in Patients with ST-Segment Elevation Myocardial Infarction

BACKGROUND

Although remote ischemic post-conditioning (RIPC) has been shown to prevent contrast-induced acute kidney injury (CIAKI) in patients with acute coronary syndrome, its efficacy in patients with ST-segment elevation myocardial infarction (STEMI) remains unclear. We examined the relationship among balloon inflations and deflations (BID) times, SYNTAX score of infarction-related artery (SI), periprocedural complications, and CIAKI in STEMI patients undergoing primary percutaneous coronary intervention (pPCI).

METHODS

Patients with STEMI undergoing pPCI with Mehran risk score (MRS) ≥ 5 were enrolled between February 2007 and September 2012. The study end point was the development of CIAKI.

RESULTS

Of 206 patients, the median age was 65 years [interquartile range (IQR): 55-77] with 72.8% male and Mehran risk score (MRS) 8 (IQR: 6-12). Receiver operating characteristic curve showed that BID times > 9 times or SI > 10 was the best cut-off associated with CIAKI. In univariate analysis, significant association with CIAKI existed in BID > 9 times [odds ratio (OR): 3.106, 95% confidence interval (CI): 1.284-7.513, p = 0.012] and SI > 10 (OR: 3.909, 95% CI: 1.570-9.735, p = 0.003). Other variables associated with CIAKI included creatinine, hemoglobin, angiotensin converting enzyme inhibitor or angiotensin receptor blocker use at discharge. In multivariate analysis, SI > 10 remained an independent predictor of CIAKI in different adjustment model, even on top of MRS (adjusted OR: 3.498, 95% CI: 1.086-11.268, p = 0.036).

CONCLUSIONS

Vascular complexity of infarct-related artery rather than higher BID times (> 9) was the major determinant of the development of CIAKI after pPCI in STEMI patients.

Longitudinal evaluation of myocardial glucose metabolism and contractile function in obese type 2 diabetic db/db mice using small-animal dynamic 18F-FDG PET and echocardiography

The aim was to evaluate sequential changes of myocardial glucose utilization and LV systolic function in db/db mice.

Eight db/db and eight wild-type mice underwent plasma substrate analysis and dynamic ¹⁸F-FDG PET at week 8 (W8), W10, W12, W14, and W16. ¹⁸F-FDG uptake constant Ki and the rate of myocardial glucose uptake (MRGlu) were derived via Patlak graphic analysis. Another 8 db/db and 8 wild-type mice received echocardiography at W8, W12, and W16 and LV structure and function were measured.

The db/db mice showed increased weights and glucose levels as they aged. The index of homeostasis model assessment-estimated insulin resistance, insulin, and free fatty acid concentrations were higher in db/db mice compared with wild-type. MRGlu of db/db mice across all time points was markedly higher than that of wild-type. An age-dependent elevation of MRGlu was observed in db/db mice. Ki and MRGlu of db/db mice showed negative correlation with triglyceride levels. When two groups were pooled together, Ki and MRGlu were significantly proportional to glucose levels. No significant difference in LV structure and function was noted between db/db and control mice.

In conclusion, we demonstrated altered myocardial glucose utilization preceding the onset of LV systolic dysfunction in db/db mice.

Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system

Quantum Hall ferromagnetic transitions are typically achieved by increasing the Zeeman energy through in-situ sample rotation, while transitions in systems with pseudo-spin indices can be induced by gate control. We report here a gate-controlled quantum Hall ferromagnetic transition between two real spin states in a conventional two-dimensional system without any in-plane magnetic field. We show that the ratio of the Zeeman splitting to the cyclotron gap in a Ge two-dimensional hole system increases with decreasing density owing to inter-carrier interactions. Below a critical density of ~2.4 × 10¹⁰ cm⁻², this ratio grows greater than 1, resulting in a ferromagnetic ground state at filling factor ν = 2. At the critical density, a resistance peak due to the formation of microscopic domains of opposite spin orientations is observed. Such gate-controlled spin-polarizations in the quantum Hall regime opens the door to realizing Majorana modes using two-dimensional systems in conventional, low-spin-orbit-coupling semiconductors.

Dunaliella salina alga extract inhibits the production of interleukin-6, nitric oxide, and reactive oxygen species by regulating nuclear factor-κB/Janus kinase/signal transducer and activator of transcription in virus-infected RAW264.7 cells

Recent investigations have demonstrated that carotenoid extract of Dunaliella salina alga (Alga) contains abundant β-carotene and has good anti-inflammatory activities. Murine macrophage (RAW264.7 cells) was used to establish as an in vitro model of pseudorabies virus-induced reactive oxygen species (ROS) response. In this study, antioxidant activities of Alga were measured based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, trolox equivalent antioxidant capacity assays, reducing power, and virus-induced ROS formation in RAW264.7 cells. Anti-inflammatory activities of Alga were assessed by its ability to inhibit the production of interleukin-6 and nitric oxide (NO) using enzyme-linked immunosorbent assay, then the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway was investigated by measuring the inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nuclear factor-κB (p50 and p65), JAK, STAT-1/3, and suppressor of cytokine signaling 3 (SOCS3) by Western blotting. In addition, Alga inhibited virus replication by plaque assay. Our results showed that the Alga had high antioxidant activity, significantly reduced the virus-induced accumulation of ROS, and inhibited the levels of nitric oxide and interleukin-6. Further studies revealed that Alga also downregulated the gene and protein expressions of iNOS, COX-2, nuclear factor-κB (p50 and p65), and the JAK/STAT pathway. The inhibitory effects of Alga were similar to pre-treatment with specific inhibitors of JAK and STAT-3 in pseudorabies virus-infected RAW264.7 cells. Alga enhanced the expression of SOCS3 to suppress the activity of the JAK/ STAT signaling pathway in pseudorabies virus-infected RAW264.7 cells. In addition, Alga has decreased viral replication (p < 0.005) at an early stage. Therefore, our results demonstrate that Alga inhibits ROS, interleukin6, and nitric oxide production via suppression of the JAK/STAT pathways and enhanced the expression of SOCS3 in virus-infected RAW264.7 cells.

Rapid and sensitive detection of Salmonella enteritidis by a pre-concentrated immunochromatographic assay in a large-volume sample system

A pre-concentrated immunochromatographic assay for Salmonella enteritidis (S. enteritidis) detection was developed based on the unique optical and magnetic properties of magnetic nanoparticles (MNPs).

[Risk factors for long-term result of endovascular treatment for auto-immune disease related abdominal aorta pseudo-aneurysm]

Objective: To summarize results of endovascular treatment for auto-immune disease related abdominal aorta pseudo-aneurysm(AIPA), and to analysis clinical predictors of long term major adverse clinical events(MACE). Methods: Retrospectively collected endovascular treatment for AIPA cases in Peking Union Medical College Hospital within 2000 to 2015. Twenty-nine cases with AIPA treated by endovascular therapy were enrolled in this study. Twenty five cases were male, range from 23 to 67 years old, mean age was (39.3±11.4) years old.Demographic characters, locations of aneurysms, type to auto-immune disease, immuno medical therapy, operation strategy and long term follow-up data were reported. Statistical analysis was made to verify clinical predictors of long-term MACE. Results: Among the 29 cases, 22 cases with bechet's disease, 4 cases with Takayasu's arteritis, 2 cases with systemic lupus erythematosus, 1 cases with polyarteritis nodosa. Eight cases had ruptured or pending ruptured pesudo-aneurysms, the rest 21 cases had dull pain or no overt symptome. Twenty-four cases had infra-renal artery aneurysms, two were para-and supra-renal artery, two were supra-celiac artery, and the rest one had multiple aneurysms involved thoracic and abdominal aorta.All the cases received regular immune medical therapy except the three emergency cases. All the operations were under general anaesthesia. Nineteen cases underwent classical Endovascular aortic aneurysm repair (EVAR), 5 cases underwent fenestration EVAR, the rest 5 cases underwent hybrid procedure. All the 29 operations were successful, without conversion to open surgery. Major peri-operation complication included 3 incision infection, 3 pulmonary infection. No death occurred. All the cases received regular follow-up from 1 to 120 months. There were five recurrence of pseudo-aneurysm, 1 case suffered from iliac limb occlusion. 5 cases received re-intervention procedure. No occlusion of revascularizal visceral artery was found during follow-up. There were 3 deaths during follow-up, with 1 aneurysm related death, the rest died due to other reasons. Single factors logical regressions analysis showed discontinuing immune medicine therapy and age no less than 40 years significantly related long-term MACE(P<0.05). Meanwhile, type of original auto-immune disease, none classical EVAR were not significant related to MACE. Conclusions: Endovascular therapy is safe and effective for AIPA. Regular peri-operation and long-term immunotherapy is key to success.

Baseline Hemoglobin Levels Associated with One-Year Mortality in ST-Segment Elevation Myocardial Infarction Patients

BACKGROUND

The association between hemoglobin (Hb) levels and mortality in patients with ST-segment elevation myocardial infarction (STEMI) remains controversial. The purpose of this study was to examine the mortality among STEMI patients with anemia or erythrocytosis, and further establish the relationship between mortality and the increment of Hb level.

METHODS

Between 2006 and 2012, 951 consecutive patients with STEMI undergoing primary percutaneous coronary intervention in a medical center in Northern Taiwan were enrolled in our study, including 535 patients with normal Hb level, 148 with anemia (male Hb ≤ 13 g/dl, female ≤ 12) and 268 with erythrocytosis (male Hb ≥ 16, female ≥ 15).

RESULTS

Patients in the anemia group were the oldest, and had higher morbidity than the normal Hb group, followed by the erythrocytosis group. In regression analyses, neither anemia nor erythrocytosis was associated with 30-day and 1-year mortality. Each 1-g/dl increment of Hb level was not associated with 30-day mortality both in patients with anemia or erythrocytosis. However, it was associated with a decreased risk of 1-year mortality in anemic patients [hazard ratio (HR): 0.756, 95% confidence interval (CI): 0.608-0.938, p = 0.011] and an increased risk of 1-year mortality in those with erythrocytosis (HR: 2.086, 95%CI: 1.106-3.937, p = 0.023). In multivariate analysis, each 1-g/dl increment of Hb level was associated with 1-year mortality both in anemic patients and those with erythrocytosis (HR: 0.788, 95%CI: 0.621-0.999, p = 0.049; HR: 2.302, 95%CI: 1.051-5.04, p = 0.037).

CONCLUSIONS

Higher hemoglobin levels in STEMI patients with anemia were associated with decreased risks of 1-year mortality, whereas higher hemoglobin levels in those with erythrocytosis were associated with increased risks of one-year mortality.

Carbon Nanodots with Sub-Nanosecond Spontaneous Emission Lifetime

Compared with most mature cadmium-containing quantum dots (QDs), carbon nanodots (CNDs) are a new class of colloidal nanomaterials that exhibit unique photoluminescence (PL) properties while being nontoxic and easily manufactured using low-cost precursor materials. However, solid-state CNDs exhibit poor PL quantum yields (PL-QYs) and inefficient radiative transition, which significantly hinders their practical use in optoelectronic devices. To address this issue, plasmonic nanoantennas consisting of Au nanorods (Au-NRs) deposited on a flat Au film with inserted dielectric layers were used to enhance the spontaneous emission of solid-state CNDs with broad spectral linewidth. Using steady-state, time-resolved, and spatial-resolved PL measurements, we found that after coupling to plasmonic nanogaps (PNGs), the PL emission was significantly enhanced, accompanied by a PL lifetime shortening to the sub-nanosecond range (≈140 ps). According to the experimental data, the radiative transition is strongly accelerated and can thus overcome the metal loss, leading to a large PL enhancement. Our demonstration can pave the way to the design of eco-friendly nanoemitters with sub-nanosecond PL lifetime for promising applications in light-emitting devices.

Relationship of serum uric acid and Killip class on mortality after acute ST-segment elevation myocardial infarction and primary percutaneous coronary intervention

BACKGROUND

There is conflicting information regarding the association between hyperuricemia and survival in STEMI patients. Our study examined the interaction between hyperuricemia and Killip class on mortality of STEMI patients.

METHODS

We analyzed 951 consecutive STEMI patients between February 2006 and September 2012. Hyperuricemia was defined as SUA of at least 7mg/dL in males and 6mg/dL in females. Killip class I patients were divided into hyperuricemia and normouricemia groups.

RESULTS

The Killip class I hyperuricemia and normouricemia groups had similar baseline and procedural characteristics, but the hyperuricemia group had significantly greater BMI, serum creatinine, and SUA, and a lower TIMI risk score (2, IQR: 1-4 vs. 3, IQR: 2-4, p=0.019). The hyperuricemia group also had greater 30-day and 1-year mortality rates (2.9% vs. 0.3%, p=0.022; 6.5% vs. 1.1%, p=0.002, respectively). However, hyperuricemia was not associated with mortality of patients in Killip classes II-IV or in the overall study population. Hyperuricemia was associated with increased mortality in subgroups of patients who were at least 65years-old, male, had BMI of 25kg/m² or less, were in Killip class I, without diabetes, and who did not receive intra-aortic balloon pump support. Hyperuricemia interacted with Killip class I in increasing the risk for 1-year mortality (p for interaction=0.038).

CONCLUSIONS

Hyperuricemia increased the 1-year mortality of STEMI patients in Killip class I, but not of patients in Killip classes II-IV. An interaction of hyperuricemia and Killip class significantly affects the mortality of STEMI patients.

Fluid mechanical dispersion of airborne pollutants inside urban street canyons subjecting to multi-component ventilation and unstable thermal stratifications

The pedestrian level pollutant transport in street canyons with multiple aspect ratios (H/W) is numerically investigated in the present work, regarding of various unstable thermal stratification scenarios and plain surrounding. Non-isothermal turbulent wind flow, temperature field and pollutant spread within and above the street canyons are solved by the realizable k-ε turbulence model along with the enhanced wall treatment. One-vortex flow regime is observed for shallow canyons with H/W=0.5, whereas multi-vortex flow regime is observed for deep canyons with H/W=2.0. Both one-vortex and multi-vortex regimes could be observed for the street canyons with H/W=1.0, where the secondary vortex could be initiated by the flow separation and intensified by unstable thermal stratification. Air exchange rate (AER) and pollutant retention time are adopted to respectively evaluate the street canyon ventilation and pollutant removal performance. A second-order polynomial functional relationship is established between AER and Richardson number (Ri). Similar functional relationship could be established between retention time and Ri, and it is only valid for canyons with one-vortex flow regime. In addition, retention time could be prolonged abruptly for canyons with multi-vortex flow regime. Very weak secondary vortex is presented at the ground level of deep canyons with mild stratification, where pollutants are highly accumulated. However, with the decrease of Ri, pollutant concentration adjacent to the ground reduces accordingly. Present research could be applied to guide the urban design and city planning for enhancing pedestrian environment.