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1.
Molecules ; 29(11)2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38893555

RESUMO

In recent years, various kinds of civil explosive detonation accidents have occurred frequently around the world, resulting in substantial human casualties and significant property losses. It is generally believed that thermal stimulation plays a critical role in triggering the detonation of explosives; consequently, the study of the thermal hazards of explosives is of great significance to many aspects of safety emergency management practices in the production, transportation, storage, and use of explosives. It is known that the thermal stability of the ammonium perchlorate-aluminium system and the ammonium nitrate-aluminium system has been extensively investigated previously in the literature. However, there is a paucity of research on the thermal hazard characteristics of non-ideal explosives under varying oxygen balance conditions within the academic sphere. Therefore, this research focused on the study of the thermal hazards of non-ideal explosives based on thermokinetic analysis. The thermal hazards of non-ideal explosive mixtures of ammonium perchlorate and aluminium and of ammonium nitrate and aluminium were studied by thermal analysis kinetics. The thermokinetic parameters were meticulously studied through differential scanning calorimetry (DSC) analysis. The results showed that the peak reaction temperature and activation energy of the ammonium perchlorate-aluminium system were significantly higher than those of the ammonium nitrate-aluminium system. Under the condition of zero oxygen balance, the peak reaction temperature of the ammonium nitrate-aluminium system was 259 °C (heating rate 5 °C/min), and the activation energy was 84.7 kJ/mol. Under the same conditions, the peak reaction temperature and activation energy of the ammonium perchlorate-aluminium system were 292 °C (heating rate 5 °C/min) and 94.9 kJ/mol, respectively. These results indicate that the ammonium perchlorate-aluminium system has higher safety under the same thermal stimulation conditions. Furthermore, research on both non-ideal explosive systems reveals that the activation energy is at its peak under negative oxygen balance conditions, recorded at 104.2 kJ/mol (ammonium perchlorate-aluminium) and 86.2 kJ/mol (ammonium nitrate-aluminium), which indicates a higher degree of safety. Therefore, the investigation into the thermal hazards of non-ideal explosive systems under different oxygen balance conditions is of utmost importance for the enhancement and improvement of safety emergency management practices.

2.
Artigo em Inglês | MEDLINE | ID: mdl-38449345

RESUMO

OBJECTIVE: We aim to examine the association between long-term cumulative health status and subsequent mortality among patients with acute heart failure (HF). METHODS: Based on a national prospective cohort study of patients hospitalized for HF, we measured health status by Kansas City Cardiomyopathy Questionnaire (KCCQ)-12 at 4 time points, i.e. admission, 1-,6- and 12-month after discharge. Cumulative health status was interpreted by cumulative KCCQ-12 score and cumulative times of good health status. Outcomes included subsequent all-cause and cardiovascular mortality. Multivariable Cox proportional hazard models were performed to examine the association between cumulative health status and subsequent mortality. RESULTS: Totally, 2328 patients (36.7% women and median age 66 [IQR: 56-75] years) were included, the median follow-up was 4.34 (IQR: 3.93-4.96) years. Compared with Quartile 4, the lowest Quartile 1 had the highest HR for all-cause mortality (2.96; 95% CI: 2.26-3.87), followed by Quartile 2 (1.79; 95% CI: 1.37-2.34) and Quartile 3 (1.62; 95% CI: 1.23-2.12). Patients with 0-time of good health status had the highest risk of all-cause mortality (HR: 2.41, 95% CI: 1.69-3.46) compared with patients with 4-times of good health status. Similar associations persisted for cardiovascular mortality. CONCLUSIONS: A greater burden of cumulative health status indicated worse survival among patients hospitalized for HF. Repeated KCCQ measurements could be helpful to monitor long-term health status and identify patients vulnerable to death. Clinical Trial Registration: www.clinicaltrials.gov (NCT02878811).

3.
Obesity (Silver Spring) ; 32(4): 822-833, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38374722

RESUMO

OBJECTIVE: This study examined the association between physical activity patterns and abdominal and general adiposity. METHODS: Data were extracted among 20- to 59-year-old participants in the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018. Abdominal and general adiposity was assessed by dual-energy x-ray absorptiometry (DXA) and anthropometric measures. DXA-measured indicators were further normalized into z scores. Physical activity levels were collected by questionnaire and classified as inactive, "weekend warrior" (WW), and regularly active (RA). Survey linear regression models were used to assess associations between physical activity patterns and adiposity indicators. RESULTS: Among 9629 participants, 772 (8.2%) reported the WW pattern and 3277 (36.9%) reported the RA pattern. Compared with inactive, both WW and RA had lower DXA-measured abdominal adiposity (WW: ß: -0.24, 95% CI: -0.38 to -0.10; RA: -0.18, 95% CI: -0.29 to -0.07), waist circumference (WW: ß: -1.94, 95% CI: -3.16 to -0.73; RA: -1.31, 95% CI: -2.32 to -0.29), whole-body fat mass (WW: ß: -0.16, 95% CI: -0.25 to -0.08; RA: -0.11, 95% CI: -0.18 to -0.04), and BMI (WW: ß: -0.78, 95% CI: -1.27 to -0.28; RA: -0.47, 95% CI: -0.89 to -0.04). CONCLUSIONS: The WW pattern was associated with similarly lower abdominal and general adiposity to the RA pattern versus the inactive pattern.


Assuntos
Adiposidade , Obesidade , Adulto , Humanos , Adulto Jovem , Pessoa de Meia-Idade , Inquéritos Nutricionais , Índice de Massa Corporal , Obesidade/diagnóstico , Circunferência da Cintura , Exercício Físico , Absorciometria de Fóton
4.
Artigo em Inglês | MEDLINE | ID: mdl-38170569

RESUMO

BACKGROUND: To examine the association between cumulative cognitive function and subsequent mortality among patients hospitalized for acute heart failure (AHF). METHODS: Based on a prospective cohort of patients hospitalized for AHF, cognitive function was measured using Mini-Cog test at admission, 1- and 12-month following discharge. Cumulative cognitive function was interpreted by cumulative Mini-Cog score and cumulative times of cognitive impairment. Outcomes included subsequent all-cause and cardiovascular mortality. RESULTS: 1 454 patients hospitalized for AHF with median follow-up of 4.76 (interquartile range [IQR]: 4.18-5.07) years were included. Tertile 1 of cumulative Mini-Cog score had the highest risk of all-cause (hazard ratio [HR]: 1.52, 95% confidence interval [CI]: 1.14-2.03) and cardiovascular mortality (HR: 1.40, 95% CI: 1.02-1.93) compared with Tertile 3; patients with ≥2 times of cognitive impairment had the highest risk of all-cause (HR: 1.34, 95% CI: 1.03-1.73) and cardiovascular mortality (HR: 1.25, 95% CI: 0.93-1.67) compared with patients without any cognitive impairment. Cumulative Mini-Cog score provided the highest incremental prognostic ability in predicting all-cause (C-statistics: 0.64, 95% CI: 0.61-0.66) and cardiovascular mortality (C-statistics: 0.63, 95% CI: 0.60-0.67) risk on the basis of Get With The Guidelines-Heart Failure score. CONCLUSIONS: Poor cumulative cognitive function was associated with increased risk of subsequent mortality and provided incremental prognostic ability for the outcomes among patients with AHF. Longitudinal assessment and monitoring of cognitive function among patients with AHF would be of great importance in identifying patients at greater risk of self-care absence for optimizing personal disease management in clinical practice.


Assuntos
Disfunção Cognitiva , Insuficiência Cardíaca , Alta do Paciente , Humanos , Insuficiência Cardíaca/mortalidade , Masculino , Feminino , Idoso , Estudos Prospectivos , Alta do Paciente/estatística & dados numéricos , Disfunção Cognitiva/mortalidade , Doença Aguda , Cognição/fisiologia , Hospitalização/estatística & dados numéricos , Pessoa de Meia-Idade , Idoso de 80 Anos ou mais , Fatores de Risco
5.
J Affect Disord ; 351: 299-308, 2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38290578

RESUMO

BACKGROUND: To examine the associations between cumulative depressive symptoms and subsequent mortality among patients hospitalized for acute hear failure (AHF). METHODS: By using data from a prospective cohort study of patients with HF, depressive symptoms were measured by using Patient Health Questionnaire-2 (PHQ-2) at admission, 1-and 12-month after discharge. Cumulative depressive symptoms were interpreted by cumulative PHQ-2 score and cumulative times of depressive symptoms. Outcomes included subsequent 3-year all-cause and cardiovascular mortality. RESULTS: We included 2347 patients with the median follow-up of 4.4 (interquartile range [IQR]: 4.0-5.0) years. Tertile 3 of cumulative PHQ-2 score had the highest risk of all-cause (hazard ratio [HR]: 1.47, 95 % confidence interval [CI]: 1.21-1.78) and cardiovascular mortality (HR: 1.51, 95 % CI: 1.21-1.89) compared with Tertile 1; patients with≥2 times of depressive symptoms had the highest risk of all-cause (HR: 1.62, 95 % CI: 1.31-2.00) and cardiovascular mortality (HR: 1.60, 95 % CI: 1.25-2.05) compared with patients without any depressive symptom. Cumulative PHQ-2 score provided the highest level of incremental prognostic ability in predicting the risk of all-cause (C-statistics: 0.64, 95 % CI: 0.62-0.66) and cardiovascular mortality (C-statistics: 0.65, 95 % CI: 0.62-0.67) on the basis of Get With The Guidelines-Heart Failure score. CONCLUSION: Cumulative depressive symptoms were associated with the increased risk of subsequent mortality and provided incremental prognostic ability for the outcomes among patients with HF. Repeated depressive symptom measurements could be helpful to monitor long-term depressive symptoms, identify targeted patients and perform psychological interventions and social support to improve clinical outcomes among patients with AHF.


Assuntos
Insuficiência Cardíaca , Alta do Paciente , Humanos , Estudos Prospectivos , Depressão/epidemiologia , Depressão/diagnóstico , Hospitalização , Prognóstico
6.
Front Pharmacol ; 13: 811372, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35645808

RESUMO

This study explored the role of metformin (MET) in regulating the polarization of alveolar macrophages to protect against acute lung injury (ALI) in rats caused by paraquat (PQ) poisoning. The in vivo studies showed that the 35 mg/kg dose of MET increased the survival rate of rats, alleviated pathological damages to the lungs and their systemic inflammation, promoted the reduction of the pro-inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels, and increased the anti-inflammatory factor IL-10 levels in the rat serum. At the same time, the MET intervention decreased the expression of M1 macrophage marker iNOS in the lungs of the PQ-poisoned rats while increasing the M2 macrophage marker, Arg1, expression. In vitro, the concentration of MET > 10 mmol/L affected NR8383 viability adversely and was concentration-dependent; however, no adverse impact on NR8383 viability was observed at MET ≤ 10 mmol/L concentration, resisting the reducing effect of PQ on NR8383 vitality. The PQ-induced NR8383 model with MET intervention showed significantly reduced secretions of IL-6 and TNF-α in NR8383, and lowered expressions of M1 macrophage markers iNOS and CD86. Additionally, MET increased IL-10 secretion and the M2 macrophage markers, Arg1 and Mrcl, expressions. Therefore, we speculate that MET could regulate alveolar macrophage polarization to protect against PQ-poisoning caused ALI.

8.
Resuscitation ; 169: 124-135, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34699924

RESUMO

AIM: Summarise the evidence regarding the safety of mechanical and manual chest compressions for cardiac arrest patients. METHODS: Two investigators separately screened the articles of EMBASE, PubMed, and Cochrane Central databases. Cohort studies and randomized clinical trials (RCTs) that evaluated the safety of mechanical (LUCAS or AutoPulse) and manual chest compressions in cardiac arrest patients were included. A meta-analysis was performed using a random effects model to calculate the pooled odds ratios (ORs) and their 95% confidence intervals (CIs). The primary outcome was the rate of overall compression-induced injuries. The secondary outcomes included the incidence of life-threatening injuries, skeletal fractures, visceral injuries, and other soft tissue injuries. RESULTS: The meta-analysis included 11 trials involving 2,818 patients. A significantly higher rate of overall compression-induced injuries was found for mechanical compressions than manual compressions (OR, 1.29; 95% CI, 1.19-1.41), while there was no significant difference between the two groups in respect of the rate of life-threatening injuries. Furthermore, both modalities shared similar incidences of sternal fractures, vertebral fractures, lung, spleen, and kidney injuries. However, compared to mechanical compressions, manual compressions were shown to present a reduced risk of posterior rib fractures, and heart and liver lesions. CONCLUSIONS: The findings suggested that manual compressions could decrease the risk of compression-induced injuries compared to mechanical compressions in cardiac arrest patients. Interestingly, mechanical compressions have not increased the risk of life-threatening injuries, whereas additional high-quality RCTs are needed to further verify the safety of mechanical chest devices. TRIAL REGISTRY: INPLASY; Registration number: INPLASY2020110111; URL: https://inplasy.com/.


Assuntos
Reanimação Cardiopulmonar , Parada Cardíaca , Parada Cardíaca Extra-Hospitalar , Traumatismos Torácicos , Parada Cardíaca/etiologia , Parada Cardíaca/terapia , Massagem Cardíaca , Humanos , Pressão , Ensaios Clínicos Controlados Aleatórios como Assunto , Tórax
9.
Ecotoxicol Environ Saf ; 223: 112571, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34352584

RESUMO

The present study investigates whether paraquat (PQ) regulates polarization of alveolar macrophages through glycolysis and promotes the occurrence of acute lung injury in rats. In vivo, the PQ intraperitoneal injection was used to construct a model of acute lung injury in rats. In vitro, the study measured the effect of different concentrations of PQ on the viability of the alveolar macrophages, and explored the polarization and glycolysis metabolism of alveolar macrophages at different time points after PQ intervention. Compared with the normal control (NC) group, the lung pathological damage in rats increased gradually after PQ poisoning, reaching a significant degree at 48 h after poisoning. The PQ-poisoned rat serum showed increased expressions of interleukin-6 (IL-6), tumor necrosis factor- α (TNF-α), and M1 macrophage marker, iNOS, while the expression of interleukin-10 (IL-10) and M2 macrophage marker, Arg1, decreased. The toxic effect of PQ on alveolar macrophages was dose- and time-dependent. Compared with the NC group, IL-6 and TNF-α in the cell supernatant gradually increased after PQ intervention, while the IL-10 content gradually decreased. The PQ intervention in alveolar macrophages increased the expression of intracellular glycolysis rate-limiting enzyme pyruvate kinase isozymes M1/M2 (PKM1/M2), lactate, lactate/pyruvate ratio, and the polarization of alveolar macrophage towards M1. Inhibition of cellular glycolysis significantly reduced the PQ-induced alveolar macrophage polarization to M1 type. Thus, PQ induced increased polarization of lung macrophages toward M1 and decreased polarization toward M2, promoting acute lung injury. Therefore, it can be concluded that PQ regulates the polarization of alveolar macrophages through glycolysis.


Assuntos
Lesão Pulmonar Aguda , Paraquat , Lesão Pulmonar Aguda/induzido quimicamente , Animais , Glicólise , Pulmão/metabolismo , Macrófagos Alveolares/metabolismo , Paraquat/toxicidade , Ratos , Fator de Necrose Tumoral alfa/metabolismo
10.
R Soc Open Sci ; 6(11): 190728, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31827826

RESUMO

The solubility of dicarbohydrazide bis[3-(5-nitroimino-1,2,4-triazole)] (DCBNT) was first measured under the different pure solvents and binary solvents by the dynamic method over the temperature range of 290-360 K at atmospheric pressure. Results in all the solvents were positively correlated with temperature, namely increased with increasing temperature. The experiment data were correlated by the Apelblat equation, the Yaws equation and the polynomial equation. The conclusion showed that these three models all agreed well with the experimental data. Simultaneously, the dissolution enthalpy, dissolution entropy and Gibbs free energy of DCBNT in different solvents were calculated from the solubility data by using the Apelblat model. The results indicate that the dissolution process of DCBNT in these solvents is driven by entropy, which provides theoretical guidance for further research on the crystallization of DCBNT.

11.
Med Sci Monit ; 25: 7376-7382, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31574078

RESUMO

BACKGROUND Gut bacterial diversity is decreased in a proportion of patients with septic shock. We attempted to validate the hypothesis that low bacterial diversity increases the risk of mortality. MATERIAL AND METHODS All patients with septic shock seen at 2 medical center from 2016 through 2019 were included in this cohort study. Total DNA was isolated from stool, and high-throughput sequencing was performed. Clinical data were extracted from patient medical records and hospital databases. Patients were grouped by gut microbiota bacterial diversity (measured by Shannon diversity index) on presentation. We used logistic regression analysis to evaluate the risk of 28-day mortality in septic patients with low Shannon diversity index. RESULTS Of the 150 patients enrolled in this study, low bacterial diversity (Shannon index <3.0) was found in 80 patients and normal diversity (Shannon index ≥3.0) was found in 70 patients. Low diversity was associated with a higher unadjusted mortality risk, compared to those with normal diversity (odds ratio [OR] 2.04, 95% confidence interval [CI] 1.35-2.83). However, this result became non-significant after adjusting the confounding factors such as age, sex, severity of disease, comorbid status, usage of probiotics, enteral nutrition, and antimicrobial drugs (OR 1.93, 95% CI 0.55-2.69). CONCLUSIONS Our study does not support that low gut bacterial diversity is an independent risk factor for mortality in intensive care unit patients with septic shock.


Assuntos
Microbioma Gastrointestinal/fisiologia , Trato Gastrointestinal/microbiologia , Choque Séptico/microbiologia , Idoso , Bactérias/genética , China , Estudos de Coortes , Fezes/microbiologia , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Estimativa de Kaplan-Meier , Masculino , Microbiota/genética , Pessoa de Meia-Idade , Razão de Chances , Estudos Retrospectivos , Fatores de Risco , Choque Séptico/mortalidade
12.
Exp Cell Res ; 383(1): 111465, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31201811

RESUMO

Sepsis is characterized as exceed inflammation response and multiple organs dysfunction. Many articles suggested that mesenchymal stem cells can alleviate the inflammation and improve the survival rate of inflammatory animal models, however, the mechanism is still unclear. This study aimed to test the hypothesis that rat adipose-derived mesenchymal stem cells (ADMSCs) produce a amount of soluble tumour necrosis factor receptor 1 (sTNFR1), which ameliorated liver injury and inflammation and increased the survival rate of septic rat model.120 adult male Sprague-Dawley rats were randomly divided into 4 groups: sham-operated (Sham), sepsis-induced by cecal ligation and puncture (CLP), shNC (injected 1 × 106 ADMSCs with transfected with scramble shRNA 1 h after CLP), and shsTNFR1 (injected 1 × 106 ADMSCs with transfected with sTNFR1 1 h after CLP). The serum sTNFR1 levels were the lowest in Sham and highest in shNC group. ADMSCs could decrease the levels of pro-inflammatory cytokines such as TNF-α, IL-6, AP-1 c-jun and NF-κB p56 after CLP administration, whereas this result was weaken by shsTNFR1 administration. Moreover, shNC had an increased levels of the anti-inflammatory factor IL-10 compared with CLP, and this change could be weakened in shsTNFR1 administration. More importantly, ADMSCs could improve the survival rate of CLP-induced septic rats. Therapeutically administered ADMSCs secrete sTNFR1, which alleviated the liver injury and inflammatory response. Additionally, ADMSCs also ameliorated the systematic inflammation and increased the survival rate of septic rats.


Assuntos
Lesão Pulmonar Aguda/prevenção & controle , Inflamação/prevenção & controle , Transplante de Células-Tronco Mesenquimais , Células-Tronco Mesenquimais/citologia , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Sepse/complicações , Lesão Pulmonar Aguda/etiologia , Lesão Pulmonar Aguda/metabolismo , Lesão Pulmonar Aguda/patologia , Animais , Ceco/cirurgia , Inflamação/etiologia , Inflamação/metabolismo , Inflamação/patologia , Ligadura , Masculino , Ratos , Ratos Sprague-Dawley , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Sepse/patologia , Sepse/cirurgia
13.
Am J Hypertens ; 30(12): 1211-1219, 2017 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-28992100

RESUMO

BACKGROUND: Prenatal lipopolysaccharide (LPS) exposure causes hypertension in rat offspring through an unknown mechanism. Here, we investigated the role of the intrarenal renin-angiotensin system (RAS) in hypertension induced by prenatal LPS exposure and also explored whether adipose tissue-derived mesenchymal stem cells (ADSCs) can ameliorate the effects of prenatal LPS exposure in rat offspring. METHODS: Sixty-four pregnant rats were randomly divided into 4 groups (n = 16 in each), namely, a control group and an LPS group, which were intraperitoneally injected with vehicle and 0.79 mg/kg LPS, respectively, on the 8th, 10th, and 12th days of gestation; an ADSCs group, which was intravenously injected with 1.8 × 107 ADSCs on the 8th, 10th, and 12th days of gestation; and an LPS + ADSCs group, which received a combination of the treatments administered to the LPS and ADSCs groups. RESULTS: Prenatal LPS exposure increased blood pressure, Ang II expression, Ang II-positive, monocyte and lymphocyte, apoptotic cells in the kidney, and induced renal histological changes in offspring; however, the LPS and control groups did not differ significantly with respect to plasma renin activity levels, Ang II levels, or renal function. ADSCs treatment attenuated the blood pressure and also ameliorated the other effects of LPS-treated adult offspring. CONCLUSIONS: Prenatal exposure to LPS activates the intrarenal RAS but not the circulating RAS and thus induces increases in blood pressure in adult offspring; however, ADSCs treatment attenuates the blood pressure increases resulting from LPS exposure and also ameliorates the other phenotypic changes induced by LPS treatment by inhibiting intrarenal RAS activation.


Assuntos
Tecido Adiposo/química , Rim/efeitos dos fármacos , Lipopolissacarídeos/toxicidade , Transplante de Células-Tronco Mesenquimais , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Sistema Renina-Angiotensina/efeitos dos fármacos , Angiotensina II/biossíntese , Angiotensina II/sangue , Animais , Apoptose/efeitos dos fármacos , Pressão Sanguínea , Feminino , Rim/patologia , Testes de Função Renal , Células-Tronco Mesenquimais , Miocárdio/patologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Ratos , Ratos Sprague-Dawley
14.
Opt Express ; 23(25): 32728-35, 2015 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-26699062

RESUMO

A pump-probe shadowgraph imaging technique was used to reveal the femtosecond-picosecond-nanosecond multitimescale fundamentals of high-quality, high-aspect-ratio (up to 287:1) microhole drilling in poly-methyl-meth-acrylate (PMMA) by a single-shot femtosecond laser Bessel beam. The propagation of Bessel beam in PMMA (at 1.98 × 108 m/s) and it induced cylindrical pressure wave expansion (at 3000-3950 m/s in radius) were observed during drilling processes. Also, it was unexpectedly found that the expansion of the cylindrical pressure wave in PMMA showed a linear relation with time and was insensitive to the laser energy fluctuation, quite different from the case in air. It was assumed that the energy insensitivity was due to the anisotropy of wave expansion in PMMA and the ambient air.

15.
Appl Opt ; 53(31): 7290-5, 2014 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-25402890

RESUMO

We studied the micromachining of high-aspect-ratio holes in poly(methylmethacrylate) using a visible double-pulse femtosecond laser based on free-electron-density adjustments. Hole depth and aspect ratio increased simultaneously upon decreasing the wavelength in the visible-light zone. When the pulse energy reached a high level, the free-electron density was adjusted by using a double-pulse laser, which induced fewer free electrons, a lower reflectivity plasma plume, and more pulse energy deposition in the solid bottom. Thus, the aspect ratio of the hole was improved considerably. At a moderate pulse energy level, a 1.3-1.4 times enhancement of both the ablation depth and the aspect ratio was observed when the double-pulse delay was set between 100 and 300 fs, probably due to an enhanced photon-electron coupling effect through adjusting the free-electron density. At a lower pulse energy level, this effect also induced the generation of a submicrometer string. In addition, the ablation rate was improved significantly by using visible double pulses.


Assuntos
Lasers , Polimetil Metacrilato/química , Polimetil Metacrilato/efeitos da radiação , Teste de Materiais , Porosidade/efeitos da radiação , Doses de Radiação , Propriedades de Superfície/efeitos da radiação
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