Influence of wind direction on the ventilation and pollutant dispersion in different 3D street canyon configurations: numerical simulation and wind-tunnel experiment

Configuration of street canyon and the wind environment have a great influence on the self-ventilation capacity of the canyon, but the couple-effect of these two factors could not be considered in the previous study. The purpose of this study is to clarify the couple effect of street canyon configuration and wind environment on the ventilation and pollutant dispersion inside the street canyon. For this purpose, five wind directions of α = 90°, 60°, 45°, 30°, and 0° (α is the angle between the approaching wind and street canyon) and three canyon configurations (flat, step-up, and step-down canyons) were considered with numerical simulation and wind-tunnel experiment. Meanwhile, ACH (air exchange rate) and NEV (net escape velocity) were used to evaluate the ventilation capacity of the canyon. The results reveal that the wind direction has a vital influence on the ventilation in the different canyon configurations. Under the parallel wind direction (α = 0°), the airflow and ventilation capacity inside the three canyons are similar. Relative difference of ACH, named as RDA ((ACH_asymmetric-ACH_symmetric)/ACH_symmetric [Formula: see text] 100%), is 1.82%. However, under the oblique (α = 30°, 45°, and 60°) and perpendicular wind direction (α = 90°), the airflow of the step-down canyon is very different from the step-up and flat canyons. In step-down canyons, reverse flow occurs under the oblique and perpendicular wind direction, and the strength of the reverse flow increases as α increases. Due to this reverse flow, the ventilation capacity of the step-down canyon is lower than that of the step-up and flat canyons. As for the ventilation capacity in the pedestrian respiration domain, the ventilation capacity of the leeward pedestrian domain (leeward NEV) is higher in the step-down canyon than in the step-up canyon and the flat canyon (when α = 90°, leeward NEV of step-down canyon is 2.47 times the flat canyon). Conversely, the ventilation capacity of the windward pedestrian domain is lower in step-down canyons than in step-up or flat canyon (when α = 90°, windward NEV of step-down canyon is 0.1 times that of step-up canyon). The aforementioned findings are helpful to understand the effects of canyon configurations together with wind directions on the airflow as well as pollutant concentration inside the canyon. Although further researches are still required to provide practical guidelines, this study present effective methodologies to quantify the influences of street configurations and wind directions on street canyon ventilation for urban design purpose.

Effect of Stepping Up to High-Dose Inhaled Corticosteroids in Patients With Asthma: UK Database Study

BACKGROUND

It is unclear whether patients with asthma benefit from stepping up to high-dose inhaled corticosteroids (ICSs).

OBJECTIVE

To determine the effectiveness of stepping up to high-dose ICSs.

METHODS

A historic cohort study of patients with asthma (≥13 years old), identified from 2 large UK electronic medical record databases, was conducted. Patients who remained on medium-dose ICSs were compared with those who stepped up from medium- to high-dose ICSs, whereas patients who stepped up from low- to medium-dose ICSs were compared with those who stepped up from low- to high-dose ICSs. Time to first severe exacerbation (primary outcome) between treatment groups was compared using multivariable Cox proportional hazards models, and the number of exacerbations and antibiotics courses was analyzed using negative binomial regression. Inverse probability of treatment weighting was used to handle confounding.

RESULTS

The mean follow-up time to first exacerbation was 2.7 ± 2.7 years for those who remained on stable medium-dose ICSs and 2.0 ± 2.2 years for those who stepped up from medium- to high-dose ICSs. A similar pattern was noted for those who stepped up from low- to medium-dose ICSs (2.6 ± 2.5 years) and from low- to high-dose ICSs (2.3 ± 2.5 years). Patients who stepped up from medium- to high-dose ICSs (n = 6879) had a higher risk of exacerbations during follow-up compared with those who remained on medium-dose ICSs (n = 51,737; hazard ratio, 1.17; 95% CI, 1.12-1.22). This was similar in patients stepping up from low- to high-dose (n = 3232) compared with low- to medium-dose (n = 12,659) ICSs (hazard ratio, 1.10; 95% CI, 1.04-1.17). A step-up to high-dose ICSs was also associated with a higher number of asthma exacerbations and antibiotics courses. No significant difference in associations was found across subgroups of patients with different blood eosinophil counts.

CONCLUSIONS

We found no evidence that a step-up to high-dose ICSs is effective in preventing future asthma exacerbations.

Interpositional vein grafting for significant size discrepancy: The important role for short, sequential grafts in step-up and step-down microvascular anastomoses

INTRODUCTION

Anastomotic vessel size discrepancy may be addressed by numerous techniques, including the end-to-side. Most of these conventional methods are less suited with larger flap vessels relative to recipients, such as the vessel-depleted oncological neck with prior radiotherapy or in supermicrosurgical techniques with perforator recipients. We describe how short segment (single or double) interpositional vein grafts can be used to safely graduate this discrepancy in a 'step-up' or 'step-down' manner.

METHODS

We conducted a retrospective review of all cases where interpositional vein grafts had been utilised. Furthermore, the technique for harvest, vessel preparation and anastomotic sequence is described.

RESULTS

Over fifteen years, 116 short segment interpositional vein grafts (in 83 patients) were employed to address vessel discrepancy. Concerning patient demographics, there were 81 male:2 female, mean age 51 years (range 27-68 years), and aetiology was oral cancer (75), trauma(7) and congenital(1). Single (50) and double (33) grafts were used for 65 arterial anastomoses (8 step-down: 57 step-up) and 18 for venous anastomoses (12 step-down: 6 step-up). Flaps employed were osteocutaneous fibula (28), anterolateral thigh (24), free ileocolon (11), radial forearm (11), SCIP (7) and others (2). Six flaps (of 83) were lost (5 arterial and 1 venous thrombosis).

CONCLUSION

Short segment interpositional vein grafts may be safely utilised for 'step-up' and 'step-down' anastomoses. Planned use in the primary case, minimum required length and meticulous preparation are fundamental for success and to dispel traditional concerns over poorer outcomes when vein grafts are used.

Small differences in tibial contact locations following kinematically aligned TKA from the native contralateral knee

PURPOSE

Kinematically aligned (KA) TKA strives to restore native limb and knee alignments without ligament release with the premise that knee function likewise will be closely restored to native to the extent enabled by the components used. This study determined differences in anterior-posterior (AP) tibial contact locations of a KA TKA performed with asymmetric, fixed bearing, posterior cruciate-retaining (PCR) components from those of the native contralateral knee and also determined the incidence of posterior rim contact of the tibial insert during a deep knee bend and a step-up.

METHODS

Both knees were imaged using single-plane fluoroscopy for 25 patients with a calipered KA TKA and a native knee in the contralateral limb. AP tibial contact locations in each compartment were determined following 3D model-to-2D image registration. Differences in mean AP tibial contact locations in each compartment between the KA TKA knees and the native contralateral knees were analysed. Contact locations either on or beyond the most posterior point of the tibial insert determined the occurrence of posterior rim contact.

RESULTS

Mean AP tibial contact locations for both native and KA TKA knees remained relatively centred in the medial compartment but moved posterior in the lateral compartment during flexion. In both the medial and lateral compartments, differences in mean AP tibial contact locations between the KA TKA knees and the native contralateral knees were more posterior and greatest at 0° flexion for both activities (4 mm, p = 0.0009 and 7 mm, p < 0.0001 for deep knee bend and 6 mm, p < 0.0001 and 8 mm, p < 0.0001 for step-up in the medial and lateral compartments, respectively). The incidence of posterior rim contact of the tibial insert was 16% (4 of 25 patients) but the lowest Oxford Knee Score was 43 for these patients. The median Oxford Knee Score for all patients was 46 (out of 48).

CONCLUSIONS

Calipered KA TKA with asymmetric, fixed bearing, PCR components resulted in mean AP tibial contact locations which were relatively centred in the compartments and differed at most from those of the native contralateral knee by approximately 15% of the AP dimension of a mid-sized tibial baseplate. Although posterior rim contact occurred in some patients, all such patients had high patient-reported outcome scores.

LEVEL OF EVIDENCE

Therapeutic, Level III.

Comparative Study of Two Cohorts of Newly Diagnosed Crohn's Disease Demonstrates Change in Therapeutic Strategies

BACKGROUND

There has been a paradigm shift in the treatment of Crohn's disease (CD) involving the rapid introduction of biologics and/or immunomodulators after diagnosis. We wished to assess whether this was applied to patients with newly diagnosed CD in a tertiary inflammatory bowel disease referral centre in Israel.

METHODS

Newly diagnosed CD patients were stratified into 2 groups: the early group was diagnosed between 2005 and 2007 and the late group was diagnosed between 2010 and 2012. Baseline demographics, medical and surgical treatments, disease course and complications during those 2 periods were analyzed.

RESULTS

Each group included 60 patients. Significantly higher rates of immunomodulators and biologics were administered to patients in the late group compared to the early group (81.7 and 36.7% compared to 56.7 and 18.3%, p = 0.004 and p = 0.021, respectively). On the other hand, steroid therapy was less prevalent in the late (36.7%) group compared to that of the early group (56.7%), p = 0.059. Medical and surgical CD outcomes, including exacerbations/hospitalizations and surgeries, were comparable for both groups.

CONCLUSIONS

There was a change in treatment strategy between 2005-2007 and 2010-2012, as reflected in higher proportions of biologics/immunomodulators for patients with newly diagnosed CD. This was associated with a steroid-sparing effect.

COPD: A stepwise or a hit hard approach?

Current guidelines differ slightly on the recommendations for treatment of Chronic Obstructive Pulmonary Disease (COPD) patients, and although there are some undisputed recommendations, there is still debate regarding the management of COPD. One of the hindrances to deciding which therapeutic approach to choose is late diagnosis or misdiagnosis of COPD. After a proper diagnosis is achieved and severity assessed, the choice between a stepwise or "hit hard" approach has to be made. For GOLD A patients the stepwise approach is recommended, whilst for B, C and D patients this remains debatable. Moreover, in patients for whom inhaled corticosteroids (ICS) are recommended, a step-up or "hit hard" approach with triple therapy will depend on the patient's characteristics and, for patients who are being over-treated with ICS, ICS withdrawal should be performed, in order to optimize therapy and reduce excessive medications. This paper discusses and proposes stepwise, "hit hard", step-up and ICS withdrawal therapeutic approaches for COPD patients based on their GOLD group. We conclude that all approaches have benefits, and only a careful patient selection will determine which approach is better, and which patients will benefit the most from each approach.

Treatment algorithms in Crohn's - up, down or something else?

Crohn's disease is a chronic, progressive and disabling condition. New therapeutic goals have emerged in Crohn's disease such as the need to look beyond symptoms by achieving mucosal healing that is known to be associated with better outcomes. Anti-TNF (Tumour Necrosis Factor) therapy is the most potent drug class to induce and maintain mucosal healing in Crohn's disease. Recent evidence indicates that the efficacy profile of thiopurines has been overestimated while the increased risk of malignancies (lymphoma, non-melanoma skin cancers, myeloid disorders) has been underestimated. Methotrexate is well-tolerated, but its potential for disease modification is unknown. Achieving mucosal healing in patients with early Crohn's disease might be the best way to change disease course and patients' life. In 2014, anti-TNF treatment should be the first-line therapy in patients with Crohn's disease who suffer from severe and/or complicated disease and in those with poor prognostic factors. In the remaining patients, a rapid step-up approach based on a tight monitoring is recommended.

Controversies in the treatment of Crohn’s disease: The case for an accelerated step-up treatment approach

The ideal treatment strategy for Crohn’s disease (CD) remains uncertain, as does the optimal endpoint of therapy. Top-down versus step-up describes two different approaches: early use of immunomodulators and biological agents in the former versus initial treatment with steroids in the latter, with escalation to immunomodulators or biological drugs in patients proven to be steroid refractory or steroid dependent. Top-down therapy has been associated with higher rates of mucosal healing. If mucosal healing proves to be associated with better long-term outcomes, such as a decreased need for hospitalization and surgery, top-down therapy may be the better approach for many patients. The main concern with the top-down approach is the toxicity of the immunomodulators and biological agents, which have been linked with infectious complications as well as an increased risk of lymphoma. It is unlikely that one strategy will be best for all patients given the underlying heterogeneity of CD presentation and severity. Ultimately, we must weigh the safety and efficacy of the therapies with the risks of the disease itself. Unfortunately our ability to risk stratify patients at diagnosis remains rudimentary. The purpose of this paper is to review the data that supports or refutes the differing treatment paradigms in CD, and to provide a rationale for an approach, termed the “accelerated step-up” approach, which attempts to balance the risks and benefits of our currently available therapies with the risk of disease related complications as we understand them in 2008.