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1.
Bioresour Technol ; 342: 125918, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34555748

RESUMO

Bacterial nanocellulose (BNC), which has tunable properties, is a precursor of nanostructured energy storage materials; however, the cost of BNC production is challenging. This study uses crude glycerol from the biodiesel industry as a carbon nutrient and first-time carbonised BNC from K. sucrofermentans that is applied in energy storage. From crude glycerol in static cultivation, 6.4 g L-1 BNC was produced with a high crystallinity index (85%) and tensile properties in comparison to conventionally used pure carbon substrates. Carbon materials were derived from the BNC retained fibrous and crystalline features with disordered porous structures. The electrochemical properties of the carbon materials have a specific capacitance of 140 F g-1. This study highlights the valorisation of waste glycerol from the biodiesel industry as a substrate for efficient BNC production and the energy storage potential of carbon derived from BNC as renewable energy materials.


Assuntos
Acetobacteraceae , Glicerol , Carbono , Celulose
2.
Nat Commun ; 12(1): 2714, 2021 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33976126

RESUMO

Durability of high-energy throughput batteries is a prerequisite for electric vehicles to penetrate the market. Despite remarkable progresses in silicon anodes with high energy densities, rapid capacity fading of full cells with silicon-graphite anodes limits their use. In this work, we unveil degradation mechanisms such as Li+ crosstalk between silicon and graphite, consequent Li+ accumulation in silicon, and capacity depression of graphite due to silicon expansion. The active material properties, i.e. silicon particle size and graphite hardness, are then modified based on these results to reduce Li+ accumulation in silicon and the subsequent degradation of the active materials in the anode. Finally, the cycling performance is tailored by designing electrodes to regulate Li+ crosstalk. The resultant full cell with an areal capacity of 6 mAh cm-2 has a cycle life of >750 cycles the volumetric energy density of 800 Wh L-1 in a commercial cell format.

4.
ACS Appl Mater Interfaces ; 12(1): 518-526, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31808675

RESUMO

Eutectic mixture (EM)-promoted MgO sorbents exhibit high CO2 sorption capacities but  experience a significant decrease in uptake after multiple sorption-regeneration cycles due to EM movement and redistribution at high temperatures. Encapsulation of a pseudoliquid, phase-changing EM promoter with MgO may thus prevent the loss of active interface by confining the EM within a fixed area inside a MgO shell. In this work, we successfully embedded an EM composed of KNO3 and LiNO3 in a MgO fiber matrix via core-shell electrospinning. The synthesized sorbent achieved relatively high and steady sorption capacities, maintaining a stable uptake of ∼20 wt % after 25 sorption-regeneration cycles. The sorbent was also characterized using various techniques including in situ transmission electron microscopy (TEM) to describe its morphology, from which it was confirmed that the eutectic salt existed in distributed hollow pockets within the MgO fiber matrix and stayed confined within these fixed areas, favorably limiting its movement and redistribution when exposed to high temperatures where it exists in the liquid form. The EM may also be described as a glue that holds the fiber together, while MgO acts as a protective shell that prevents structural changes and rearrangement caused by EM movement, allowing the sorbent to retain its cyclic stability after multiple cycles and demonstrating its potential for industrial use after further improvement. Thus, the microencapsulation of a phase-changing EM material with pure MgO metal oxide was successfully achieved and might be explored for various material applications.

5.
Ann Plast Surg ; 83(4S Suppl 1): S74-S76, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31513071

RESUMO

Care provided to the Asian rhinoplasty patient may be multidisciplinary at times, including not only plastic surgeons, but also other health care professionals. It is crucial that all physicians caring for these patients practice complete awareness of the patient's prior operations and details of materials used in order to optimize results and avoid potentially devastating complications. These complications include but are not limited to implant infection and extrusion. Here the authors describe one such case report, discussing dermatologic biopsy of a silicone implant of the nasal tip and dorsum and subsequent revision rhinoplasty with implant removal and costochondral graft placement.


Assuntos
Povo Asiático , Próteses e Implantes/efeitos adversos , Rinoplastia/métodos , Adulto , Biópsia , Feminino , Humanos , Reoperação , Costelas/transplante , Silicones
6.
ACS Omega ; 4(2): 4129-4137, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-31459621

RESUMO

To address the instability and repulsive interaction of carbon nanotubes (CNTs) in Li-ion batteries, mixed polymers (polyacrylonitrile and polyvinylpyrrolidone) were employed as matrix support to ensure that CNT particles remain in place during charge/discharge process and prevent particle migration. Various CNT-based anodes have been reported, but these require metal support that could result in contact resistance. Hence, free-standing CNT electrodes are an attractive option. A simple method of electrospinning polymers and calcination at 800 °C is presented with CNT loading as high as 50 wt % can be obtained without binder and acts as main active material rather than an additive as described in previous studies. The anode [pyrolyzed polymer (PP)-CNT] showed excellent performance with a high discharge specific capacity of 960 mA h/g at a current density of 200 mA/g. The capacity at a higher current density (1600 mA/g) remained greater than graphite (372 mA h/g) at 521 mA h/g and showed a high stability for 675 cycles without exhibiting any significant capacity loss with a Coulombic efficiency of >95%. A rate capability experiment showed the reversibility of PP-CNTs after subjecting them to an increasing current density and regaining >95% of the initial capacity at a low current density (200 mA/g). The high capacitive performance of the material is attributed to the high loading of CNTs and their containment within the bulk of the polymer matrix to prevent particle migration and agglomeration as well as the capacity of the nanofibers to preserve a tight proximity of the electrolyte-electrode interface.

7.
Ann Plast Surg ; 81(6S Suppl 1): S30-S34, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30247189

RESUMO

The nose, with its conspicuous location, intricate convexities, and delicate 3-dimensional structure, continues to challenge the reconstructive surgeon. Today, there are a myriad of options available for reconstruction. The practitioner must take into account the location of the defect as well as the components needed to be restored. This article addresses the current practices in nasal reconstruction, including the different strategies for skin coverage, nasal lining, and structural support. We discuss both the newest techniques as well as basic principles of this long-standing procedure.


Assuntos
Rinoplastia/métodos , Humanos , Transplante de Pele , Retalhos Cirúrgicos
8.
Ann Plast Surg ; 81(6S Suppl 1): S35-S38, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-29846213

RESUMO

Condylar fractures account for one third of all mandibular fractures. Despite being highly prevalent, treatment of these fractures remains controversial because of the sequelae of inadequate closed reduction and the risks associated with open repair. Multiple studies attempt to compare closed reduction with maxillomandibular fixation (MMF), open reduction with internal fixation, and endoscopic reduction with internal fixation. In our practice, we favor closed reduction with MMF except in cases of significantly displaced subcondylar fractures. To decrease operative MMF time, we moved away from traditional arch bars in favor of intermaxillary fixation screws (IMF screws). However, since the advent of the Stryker SMARTLock Hybrid Maxillomandibular Fixation System (Hybrid), we now use this system to maximize the advantages of having an arch bar, with its flexibility of elastic placement and ability to serve as tension band, in addition to the speed and simplicity of application similarly afforded by the IMF screws. The Hybrid system is shown to be cost effective compared with arch bars in a previous study. This is attributed to decreased operating room time. There are no studies comparing its outcomes and cost with IMF screws. In this article, we examine a series of patients treated with closed reduction using either IMF screws or the Stryker SMARTLock Hybrid Maxillomandibular Fixation System. We found similar result in patient outcomes and operative time, but increase cost with the Hybrid system.


Assuntos
Parafusos Ósseos , Redução Fechada/instrumentação , Técnicas de Fixação da Arcada Osseodentária/instrumentação , Côndilo Mandibular/lesões , Côndilo Mandibular/cirurgia , Fraturas Mandibulares/cirurgia , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Duração da Cirurgia , Estudos Retrospectivos , Adulto Jovem
9.
Dalton Trans ; 47(3): 852-858, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29251306

RESUMO

A new innovative electrode material (Fe-P800) consisting of a metal complex anchored on carbon via the utilization of iron-porphyrin conjugated microporous polymer (Fe-CMP) was prepared after pyrolyzing at 800 °C. The usage of the polymer with iron-porphyrin repeating units maximized the possible formation of Fe-Nx coordination within the bulk of the sample while the thermal treatment rendered the carbon framework to form a distinct arrangement between metal, nitrogen and carbon with a high surface area of 450 m2 g-1. The formation of the M-N-C bond, confirmed through XPS analysis, established a direct interaction between metal and carbon material. Thus, an indisputable synergistic effect was observed leading to a high capacitance of 182 F g-1 at a current density of 1 A g-1 despite its low metal loading of ∼1%. It also exhibited a highly robust cycling stability of ∼100% capacitance retention even after 5000 cycles (10 A g-1). In this study, a new mechanism was proposed wherein the metal (iron) center features an electron access point via its highly reversible redox reactivity, providing a shuttle effect for charge transfer to the conductive graphitic carbon matrix.

10.
J Craniofac Surg ; 26(4): 1097-101, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26010104

RESUMO

BACKGROUND: Military pediatric plastic surgery humanitarian missions in the Western Hemisphere have been initiated and developed since the early 1990 s using the Medical Readiness Education and Training Exercise (MEDRETE) concept. Despite its initial training mission status, the MEDRETE has developed into the most common and advanced low level medical mission platform currently in use. The objective of this study is to report cleft- and craniofacial-related patient outcomes after initiation and evolution of a standardized treatment protocol highlighting lessons learned which apply to civilian plastic surgery missions. METHODS: A review of the MEDRETE database for pediatric plastic surgery/cleft and craniofacial missions to the Dominican Republic from 2005 to 2009 was performed. A multidisciplinary team including a craniofacial surgeon evaluated all patients with a cleft/craniofacial and/or pediatric plastic condition. A standardized mission time line included predeployment site survey and predeployment checklist, operational brief, and postdeployment after action report. Deployment data collection, remote patient follow-up, and coordination with larger land/amphibious military operations was used to increase patient follow-up data. Data collected included sex, age, diagnosis, date and type of procedure, surgical outcomes including speech scores, surgical morbidity, and mortality. RESULTS: Five hundred ninety-four patients with cleft/craniofacial abnormalities were screened by a multidisciplinary team including craniofacial surgeons over 4 years. Two hundred twenty-three patients underwent 330 surgical procedures (cleft lip, 53; cleft palate, 73; revision cleft lip/nose, 73; rhinoplasty, 15; speech surgery, 24; orthognathic/distraction, 21; general pediatric plastic surgery, 58; fistula repair, 12). Average follow-up was 30 months (range, 1-60). The complication rate was 6% (n = 13) (palate fistula, lip revision, dental/alveolar loss, revision speech surgery rate). The average pre-surgical (Pittsburgh Weighted Speech Score) speech score was 12 (range, 6-24). The average postsurgical speech score was 6 (range, 0-21). Average hospital stay was 3 days for cleft surgery. There were no major complications or mortality, 1 reoperation for bleeding or infection, and 12 patients required secondary operations for palatal fistula, unsatisfactory aesthetic result, malocclusion, or velopharygeal dysfunction. CONCLUSIONS: Military pediatric plastic surgery humanitarian missions can be executed with similar home institution results after the initiation and evolution of a standardized approach to humanitarian missions. The incorporation of a dedicated logistics support unit, a dedicated operational specialist (senior noncommissioned officer), a speech language pathologist, remote internet follow up, an liaison officer (host nation liaison physician participation), host nation surgical resident participation, and support from the embassy, Military Advisory Attachment Group, and United States Aid and International Development facilitated patient accurate patient evaluation and posttreatment follow-up. Movement of the mission site from a remote more austere environment to a centralized better equipped facility with host nation support to transport patients to the site facilitated improved patient safety and outcomes despite increasing the complexity of surgery performed.


Assuntos
Fenda Labial/cirurgia , Fissura Palatina/cirurgia , Missões Médicas/organização & administração , Militares , Procedimentos de Cirurgia Plástica/métodos , Cirurgia Plástica/organização & administração , Adolescente , Criança , Pré-Escolar , República Dominicana , Feminino , Humanos , Lactente , Masculino , Estados Unidos
11.
J Plast Reconstr Aesthet Surg ; 67(8): 1055-62, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24933239

RESUMO

The Tessier number 3 cleft is one of the most intricate and destructive of all facial clefts, presenting surgeons with a difficult task for reconstruction. We present a series of 10 patients with this rare cleft all treated by a single surgeon over 30 years. All patients with Tessier number 3 clefts treated between 1978 and 2008 by the senior surgeon were reviewed. Demographic data and all associated clinical findings including cranial and extracranial anomalies were recorded. Methods used to reconstruct each patient were also noted. Seven males and three females were identified and age at initial treatment ranged from 12 months to 12 years. Mean follow-up was 6.3 years. Multiple craniofacial anomalies were appreciated including other rare facial clefts, hypertelorbitism, lacrimal obstruction, anophthalmia, choanal atresia, and hemifacial microsomia. Amniotic banding was the most prominent extracranial finding noted in these patients. Tessier number 3 clefts can be associated with multiple other craniofacial anomalies making reconstruction challenging. Soft tissue and bony reconstruction must be considered separately, and a variety of tools may be employed to accomplish each goal. As the presentation can be highly variable, an individualized treatment plan must be made to meet each patient's specific needs.


Assuntos
Anormalidades Craniofaciais/classificação , Anormalidades Craniofaciais/cirurgia , Face/anormalidades , Face/cirurgia , Procedimentos de Cirurgia Plástica/métodos , Anormalidades Múltiplas/classificação , Anormalidades Múltiplas/cirurgia , Adolescente , Síndrome de Bandas Amnióticas/complicações , Transplante Ósseo , Criança , Pré-Escolar , Feminino , Seguimentos , Humanos , Lactente , Masculino , Anormalidades da Boca/complicações , Anormalidades da Boca/cirurgia , Estudos Retrospectivos , Retalhos Cirúrgicos , Adulto Jovem
12.
J Plast Reconstr Aesthet Surg ; 66(8): 1088-95, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23680116

RESUMO

Little is written about the spectrum of late radiation-induced craniofacial abnormalities and the guidelines for treating these abnormalities. The clinical records of 13 patients (eight males and five females) who received childhood craniofacial radiation between birth and 11 years of age and who subsequently had reconstructive surgery were reviewed. Eleven patients had their irradiation at the age from 1 to 5 years. The other two patients received their treatment at a relatively older age (9 and 11 years). Their deformities ranged from isolated soft-tissue deficiency with no or minimal bony deficiency to cases having osseous deformities with or without soft-tissue deficiency but still the normal or near-normal craniofacial form can be obtained with surgical intervention and the outermost extreme of the deformity is the patients whose normal or near-normal craniofacial form and function cannot be regained even with much sophisticated surgeries. Our new classification is based on two factors: the tissue component of the deformity and the possibility of regaining a normal or near-normal craniofacial form and function with the planned surgical intervention. Based on this classification, a new treatment algorithm was created.


Assuntos
Algoritmos , Assimetria Facial/classificação , Neoplasias de Cabeça e Pescoço/terapia , Procedimentos de Cirurgia Plástica , Lesões por Radiação/classificação , Tecido Adiposo/transplante , Adolescente , Adulto , Transplante Ósseo , Criança , Pré-Escolar , Assimetria Facial/etiologia , Assimetria Facial/cirurgia , Ossos Faciais/efeitos da radiação , Ossos Faciais/cirurgia , Músculos Faciais/efeitos da radiação , Músculos Faciais/cirurgia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Lesões por Radiação/etiologia , Lesões por Radiação/cirurgia , Radioterapia/efeitos adversos , Pele/efeitos da radiação , Transplante de Pele , Crânio/efeitos da radiação , Crânio/cirurgia , Retalhos Cirúrgicos , Adulto Jovem
13.
Ann Plast Surg ; 70(3): 296-300, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23038138

RESUMO

BACKGROUND: The philtrum and the Cupid's bow are the most prominent features of the upper lip and are crucial for normal appearance. Unfortunately, projection of the philtral column is a common deficiency of the repaired cleft lip. Although a multitude of methods for constructing the philtral dimple and ridge have been described, no single procedure has achieved complete satisfactory results. The authors describe their technique for construction of the philtral column using palmaris longus tendon. METHODS: Between 1998 and 2009, a retrospective study was performed for identifying patients with depression of the philtral scar following cleft lip repair. Pre- and postoperative photographs were taken with at least 6 months follow-up. Postoperative patient satisfaction and occurrence of complications are reported. RESULTS: In all, 17 patients who developed depression of the philtral ridge following cleft lip repair underwent philtral reconstruction utilizing palmaris longus tendon grafts by the senior author (H.K.K.). At the time of surgery, average age for 11 females and 6 males was 18.5 years. The follow-up period ranged from 6 to 126 months, with an average of 42.3 months. In the early postoperative period, 2 complications in the form of graft exposure occurred. However, both cases were successfully managed with preservation of the graft. All patients were satisfied with their long-term results, and none required further surgery. CONCLUSIONS: The use of palmaris longus tendon graft is an effective, reproducible, and safe method by which to construct the philtral column in the secondary cleft lip deformity.


Assuntos
Fenda Labial/cirurgia , Lábio/cirurgia , Procedimentos de Cirurgia Plástica/métodos , Tendões/transplante , Adolescente , Adulto , Feminino , Seguimentos , Humanos , Masculino , Satisfação do Paciente , Estudos Retrospectivos , Retalhos Cirúrgicos , Adulto Jovem
14.
J Craniofac Surg ; 23(7 Suppl 1): 1950-3, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23154375

RESUMO

The primary mission of the US Navy (USN) is to maintain superior naval forces capable of winning wars, deterring aggression, and maintaining freedom of the seas. However, a major core capability of the present-day USN includes the ability to effectively and rapidly provide humanitarian assistance and disaster response whenever the need arises. Occurring annually since 2006, Pacific Partnership is an ongoing USN operation that aims to strengthen regional alliances and improve delivery of humanitarian assistance and disaster relief. A major focus of Pacific Partnership 2010 was the delivery of medical care to underserved communities in the region. A significant portion of the medical mission was specifically directed toward the treatment of patients with cleft lip and palate. As the main operational platform, the USN Ship Mercy provided an unparalleled environment in which to provide state-of-the-art multidisciplinary treatment to patients with cleft lip and palate. With the cooperation of host nations and locally active nongovernmental organizations, a sustainable model for providing treatment for cleft lip and palate can be developed.


Assuntos
Altruísmo , Fenda Labial/cirurgia , Fissura Palatina/cirurgia , Missões Médicas , Adolescente , Adulto , Sudeste Asiático , Criança , Pré-Escolar , Comportamento Cooperativo , Procedimentos Clínicos , Tempestades Ciclônicas , Atenção à Saúde , Desastres , Terremotos , Feminino , Humanos , Lactente , Masculino , Programas de Rastreamento , Área Carente de Assistência Médica , Ciência Militar , Organizações , Parcerias Público-Privadas , Socorro em Desastres , Navios , Estados Unidos , Adulto Jovem
15.
J Cutan Aesthet Surg ; 5(3): 193-6, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23112516

RESUMO

Injected liquid silicone continues to be employed by unscrupulous practitioners in many parts of the world for the purpose of breast augmentation. Complications vary; however, inflammation, foreign body reaction, and granuloma formation often lead to painful and disfigured breasts. Furthermore, migrations of silicone to remote tissues cause additional problems. We present a review of cases and propose an updated algorithm for the diagnosis and management silicone mastitis. We describe two representative cases of mastitis cause by injected liquid silicone. Patients uniformly developed inflammation and granuloma formation causing painful and disfigured breasts. Each patient required bilateral mastectomy and breast reconstruction. Although injection of liquid silicone has been condemned by the legitimate medical community for the purpose of breast augmentation, it continues to be illicitly performed and there exists a sizable patient population suffering from the complications of this procedure. Accurate identification requires a high index of suspicion in patients presenting with firm and painful breasts. An aggressive management strategy is recommended in the setting of silicone mastitis due to the risk of obscuring malignancy.

16.
J Craniofac Surg ; 23(4): 1061-6, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22777454

RESUMO

Patients with congenital craniofacial malformations present with complex challenges for reconstruction. Successful management requires individualized treatment often involving rebuilding the facial skeleton de novo, as well as correcting the overlying soft-tissue deficiencies in the final stages. At the University of California, Los Angeles (UCLA) Craniofacial Clinic, serial autologous fat transplantation performed during staged reconstruction is the preferred method.A total of 27 patients with a diagnosis of either craniofacial microsomia/Goldenhar (CM) (n = 19) or Treacher Collins syndrome (TC) (n = 8) were treated at the UCLA Craniofacial Clinic by autologous fat transfer between July 1999 and February 2009. Two-dimensional analysis was conducted on standardized preoperative and postoperative photographs to determine facial symmetry for every patient. Results was grouped based on pathology and analyzed by comparing adipocyte donor site (abdomen vs other).The mean ages at the time of first fat transfer were 17 years for the CM group and 15 years for the TC group. The average numbers of fat transfers per patient were 2.05 (CM) and 2.12 (TC). A mean of 3.74 procedures other than fat grafting was performed in each CM patient, whereas 4.38 other procedures were performed in each TC patient. In CM patients, less than 10.5 months between procedures resulted in improved symmetry. There was an average 6.63% improvement in facial symmetry in the CM group, and a 7.67% improvement in the TC group.Based on the UCLA experience, the durability of facial asymmetry and contour correction with fat transplantation is attainable in the craniofacial patient but may also require concomitant skeletal correction in the most severe cases.


Assuntos
Tecido Adiposo/transplante , Síndrome de Goldenhar/cirurgia , Disostose Mandibulofacial/cirurgia , Procedimentos de Cirurgia Plástica/métodos , Adolescente , California , Feminino , Humanos , Masculino , Fotografação , Estatísticas não Paramétricas , Transplante Autólogo , Resultado do Tratamento
18.
Appl Opt ; 50(4): A90-9, 2011 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21283225

RESUMO

We describe the implementation of a mid-infrared laser-based trace gas sensor with a photoreaction chamber, used for reproducing chemical transformations of benzene, toluene, and p-xylene (BTX) gases that may occur in the atmosphere. The system performance was assessed in the presence of photoreaction products including aerosol particles. A mid-infrared external cavity quantum cascade laser (EC-QCL)-tunable from 9.41-9.88 µm (1012-1063 cm(-1))-was used to monitor gas phase concentrations of BTX simultaneously and in real time during chemical processing of these compounds with hydroxyl radicals in a photoreaction chamber. Results are compared to concurrent measurements using ultraviolet differential optical absorption spectroscopy (UV DOAS). The EC-QCL based system provides quantitation limits of approximately 200, 200, and 600 parts in 10(9) (ppb) for benzene, toluene, and p-xylene, respectively, which represents a significant improvement over our previous work with this laser system. Correspondingly, we observe the best agreement between the EC-QCL measurements and the UV DOAS measurements with benzene, followed by toluene, then p-xylene. Although BTX gas-detection limits are not as low for the EC-QCL system as for UV DOAS, an unidentified by-product of the photoreactions was observed with the EC-QCL, but not with the UV DOAS system.


Assuntos
Atmosfera/análise , Benzeno/análise , Monitoramento Ambiental/instrumentação , Lasers , Análise Espectral/instrumentação , Tolueno/análise , Xilenos/análise , Benzeno/efeitos da radiação , Sistemas Computacionais , Desenho de Equipamento , Análise de Falha de Equipamento , Raios Infravermelhos , Fotoquímica/instrumentação , Tolueno/efeitos da radiação , Xilenos/efeitos da radiação
19.
Appl Opt ; 49(28): 5302-8, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20885466

RESUMO

A pulsed, distributed feedback (DFB) quantum cascade (QC) laser centered at 970 cm(-1) was used in combination with an off-axis cavity enhanced absorption (CEA) spectroscopic technique for the detection of ammonia and ethylene. Here, the laser is coupled into a high-finesse cavity with an optical path length of ∼76 m. The cavity is installed into a 53 cm long sample cell with a volume of 0.12 L. The laser is excited with short current pulses (5-10 ns), and the pulse amplitude is modulated with an external current ramp, resulting in a ∼0.3 cm(-1) frequency scan. A demodulation approach followed by numerical filtering was utilized to improve the signal-to-noise ratio. We demonstrated detection limits of ~15 ppb and ∼20 ppb for ammonia and ethylene, respectively, with less than 5 s averaging time.

20.
Appl Opt ; 49(6): 945-9, 2010 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-20174162

RESUMO

We demonstrate the application of a commercially available widely tunable continuous-wave external cavity quantum cascade laser as a spectroscopic source for the simultaneous detection of multiple gases. We measured broad absorption features of benzene and toluene between 1012 and 1063 cm(-1) (9.88 and 9.41 microm) at atmospheric pressure using an astigmatic Herriott multipass cell. Our results show experimental detection limits of 0.26 and 0.41 ppm for benzene and toluene, respectively, with a 100 m path length for these two gases.

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