Onset of cellular instabilities in spherically propagating hydrogen-air premixed laminar flames

Using high-speed Schlieren and Shadow photography, the instabilities of outwardly propagating spherical hydrogen-air flames have been studied in a constant volume combustion bomb. Combustion under different equivalence ratios (0.2 w 1.0), temperatures (298 K w 423 K) and pressures (1.0 bar w 10.0 bar) is visualized. The results show that flames experience both unequal diffusion and/or hydrodynamic instabilities at different stages of propagation. The critical flame radius for such instabilities is measured and correlated to the variations of equivalence ratio, temperature and pressure. Analysis revealed that equivalence ratio affects unequal diffusion instability via varying the Lewis number, Le; increased temperature can delay both types of instabilities in the majority of tests by promoting combustion rate and changing density ratio; pressure variation has minor effect on unequal diffusion instability but is responsible for enhancing hydrodynamic instability, particularly for stoichiometric and near-stoichiometric flames

Acupotomy Therapy for Chronic Nonspecific Neck Pain: A Systematic Review and Meta-Analysis

Objective. This review is to assess the efficacy and safety of acupotomy therapy in chronic nonspecific neck pain. Methods. We searched six computerised databases. Randomized controlled trials incorporating acupotomy therapy alone or combined with other conventional treatments for chronic nonspecific neck pain were included. Two reviewers screened each literature and extracted data independently according to Cochrane Reviews’ Handbook (5.1). The Cochrane Collaboration’s RevMan 5.3 software was applied for meta-analysis. Results. A total of ten trials involving 433 patients were enrolled. The pooled analysis indicated that acupotomy therapy showed a significant improving short-term and long-term effect on effective rate and cure rate. Meta-analysis demonstrated that acupotomy therapy group was superior to control group in restoring cervical lordosis and debasing VAS score. The result of continuous data did not support statistical significance of acupotomy therapy in adjusting clinical symptom score. For adverse events, acupotomy group did not reveal obvious superiority compared to control group. Conclusions. Acupotomy therapy may be beneficial to chronic nonspecific neck pain patients. To strengthen supportive evidence, future, more rigorously designed clinical trials, adequate adverse events, and follow-up project are recommended

Study of laminar combustion characteristics of gasoline surrogate fuel-hydrogen-air premixed flames

This paper investigated the effects of hydrogen addition to gasoline surrogates fuel-air mixture on the premixed spherical flame laminar combustion characteristics. The experiments were carried out by high speed Schlieren photography on a constant-volume combustion vessel. Combining with nonlinear fitting technique, the variation of flame propagation speed, laminar burning velocity, Markstein length, flame thickness, thermal expansion coefficient and mass burning flux were studied at various equivalence ratios (0.8–1.4) and hydrogen mixing ratios (0%–50%). The results suggested that the nonlinear fitting method had a better agreement with the experimental data in this paper and the flame propagation was strongly effected by stretch at low equivalence ratios. The stretched propagation speed increased with the increase of hydrogen fraction at the same equivalence ratio. For a given hydrogen fraction, Markstein length decreased with the increase of equivalence ratio; flame propagation speed and laminar burning velocity first increased and then decreased with the increase of equivalence ratio while the peaks of the burning velocity shifted toward the richer side with the increase of hydrogen fraction

Association of Depression/Anxiety Symptoms with Neck Pain: A Systematic Review and Meta-Analysis of Literature in China

Background. Due to its high morbidity and prevalence, the potential relationships of depression/anxiety symptoms in neck pain (NP) are not well demonstrated. Objectives. This study aimed to conduct a comprehensive estimation of controlled trials of psychological problems and to test hypotheses concerning whether NP was statistically relative to anxiety/depression symptoms. Methods. Chinese literature databases such as the China National Knowledge Infrastructure (CNKI), VIP Information (VIP), Chinese Biomedicine (CBM), and Wanfang Data (WANFANG) were scientifically searched for reports published until February 5, 2018. Controlled trials incorporating NP patients with anxiety/depression versus healthy people were contained. Two researchers screened each article and extracted data, respectively, and blinded to the findings of each other. Meta-analysis was conducted by the Cochrane Collaboration’s RevMan 5.3 and Stata 14.0 (Stata Corp LP, USA) software. Results. We identified 13 eligible studies involving 2339 patients and 3290 healthy people. Compared with healthy control participants, the findings indicated that depression/anxiety symptoms were more common or severe in NP patients (respectively, SMD = 0.89; 95% CI = (0.58, 1.20); P<0.01 and SMD = 0.92; 95% CI = (0.65, 1.20); and P<0.01), results from the pooled data demonstrated no statistical significance between depression/anxiety symptoms and gender in NP patients (resp., SMD = 0.16; 95% CI = (−0.18, 0.51); P=0.35 and SMD = −0.08; 95% CI = (−0.42, 0.27); and P=0.67), and the combined data of the incidence of depression or anxiety symptoms revealed significant difference between NP patients and healthy persons (resp., RR = 4.81; 95% CI = (3.30, 7.01); P<0.01 and RR = 3.29; 95% CI = (2.16, 5.00); and P<0.01). In addition, we did not find articles that met the inclusion criteria, which compared NP patients with other physical illnesses in terms of anxiety/depression symptoms. Conclusions. This meta-analysis suggests that anxiety/depression symptoms are associated with high morbidity in NP patients. We consider these reports support the viewpoint that nonspecific mechanisms mediate mental disturbances in NP. This study may have clinical value for NP, offering an underlying target for the prevention and treatment of anxiety/depression