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1.
JAMA Otolaryngol Head Neck Surg ; 149(12): 1147-1148, 2023 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-37733354

RESUMEN

A 13-month-old male presents with a firm left anterior tongue mass noted since birth that has increased proportionally with the child's growth. What is your diagnosis?


Asunto(s)
Úlceras Bucales , Enfermedades de la Lengua , Humanos , Lengua , Enfermedades de la Lengua/diagnóstico , Enfermedades de la Lengua/cirugía
2.
Opt Express ; 30(6): 10087-10095, 2022 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-35299419

RESUMEN

A compact, ultra-broadband and high-performance silicon TE-pass polarizer is proposed and demonstrated experimentally. It is based on partially-etched (ridge) waveguide adiabatic S-bends, input/output tapers and side gratings on a silicon-on-insulator (SOI) platform. A compact footprint and weak back reflections are obtained due to the bent waveguide and the tapers, respectively. An extremely high extinction ratio is achieved by scattering the undesired light in the slab section using the side gratings. The 3D FDTD simulations show a TE loss less than 0.3 dB and an extinction ratio greater than 30 dB over a 500 nm wavelength range (1200 nm to 1700 nm). Measured results show a high TM loss (> 35 dB) and a low TE insertion loss (< 1.5 dB), over a 200 nm wavelength range (1450 nm to 1650 nm). The measured TE loss is < 0.6 dB at a communication wavelength of 1550 nm. The footprint of the optimized design is 65 µm × 20 µm.

3.
Otol Neurotol ; 42(4): e459-e463, 2021 04 01.
Artículo en Inglés | MEDLINE | ID: mdl-33347050

RESUMEN

OBJECTIVE: Chronic ear disease presents a unique challenge to otolaryngologists in both rural and urban settings. Cholesteatoma remains a difficult disease to treat in rural populations due to limited healthcare access and high risk of recurrence. The purpose of this study was to determine if there are differences in surgical outcomes among patients with acquired cholesteatoma residing in rural versus urban settings. STUDY DESIGN: Single-surgeon retrospective case series with chart review. SETTING: Tertiary care private otolaryngology practice. PATIENTS: One hundred twenty-two patients presenting to the Kentuckiana ENT otology and neurotology practice from January 2011 to May 2017. MAIN OUTCOME MEASURES: Surgical outcomes including recurrence, air-bone gap improvement, ossicular integrity, and complications were reviewed and compared between the rural and urban cohorts. RESULTS: Presence of postoperative residual cholesteatoma (OR = 8.667, 95% CI = 2.022-37.141, p = 0.008) and number of surgeries per patient (OR = 5.185, 95% CI = 1.086-24.763, p = 0.024) were significantly increased among patients in rural nonmetropolitan areas. No significant differences were found when comparing risk of recurrence, size of cholesteatoma, presence of complications, air-bone gap improvement, and ossicular chain integrity. There were significantly more second-look surgeries performed in privately insured patients (OR = 8.582, 95% CI = 1.937-38.017, p = 0.001). CONCLUSIONS: Patients in rural communities have an increased number of surgeries and postoperative risk for residual cholesteatoma compared to patients residing in urban settings. This study provides the basis for larger, multicenter, prospective examinations of outcomes among urban versus rural patients, which would enable a better understanding of difference in surgical outcomes between rural and urban cohorts.Level of Evidence: IV.


Asunto(s)
Colesteatoma del Oído Medio , Población Rural , Colesteatoma del Oído Medio/epidemiología , Colesteatoma del Oído Medio/cirugía , Humanos , Estudios Prospectivos , Estudios Retrospectivos , Resultado del Tratamiento , Población Urbana
4.
Otolaryngol Head Neck Surg ; 164(6): 1160-1165, 2021 06.
Artículo en Inglés | MEDLINE | ID: mdl-33138688

RESUMEN

OBJECTIVE: Ballistic injuries to the temporal bone are uncommon but devastating injuries that damage critical neurovascular structures. This review describes outcomes after ballistic injuries to the temporal bone and offers initiatives for standardized high-quality future research. DATA SOURCES: A systematic search of PubMed, Embase, and Cochrane. REVIEW METHODS: Studies in the review included adults who experienced temporal bone fractures due to gunshot wounds and survived longer than 48 hours. Individual case reports were excluded. The various searches returned 139 results, of which 6 met inclusion criteria. RESULTS: Most of the included studies are case series with low-level evidence that report a wide range of outcomes and follow-up. Outcomes include demographic patient information, audiologic outcomes, vascular injuries, intracranial complications, facial nerve function, and surgical indications. CONCLUSION: This review is the first to characterize the nature and progression of patients who experienced gunshot wounds to the temporal bone. Although all patients share an etiology of injury, they often have vastly different hospital courses and outcomes. This review provides a basis for future studies to guide care for these injuries, as most of the existing literature includes small dated case series.


Asunto(s)
Fracturas Óseas/etiología , Hueso Temporal/lesiones , Heridas por Arma de Fuego/complicaciones , Fracturas Óseas/complicaciones , Humanos
5.
J Manag Care Spec Pharm ; 23(12): 1221-1226, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-29172983

RESUMEN

BACKGROUND: Filgrastim-sndz, a granulocyte-colony stimulating factor (G-CSF), was introduced as a biosimilar to filgrastim in 2015, but real-world comparative effectiveness for filgrastim versus filgrastim-sndz has not been reported to date. OBJECTIVES: To (a) compare the incidence of febrile neutropenia for patients taking filgrastim versus those taking filgrastim-sndz and (b) compare the incidence of a potential serious adverse event for filgrastim versus filgrastim-sndz. METHODS: This retrospective cohort study identified patients receiving a G-CSF following chemotherapy, using administrative claims from the Humana Research Database. Patients enrolled in a Medicare Advantage Prescription Drug plan with a claim for a G-CSF from October 1, 2015, through September 30, 2016, were identified. G-CSF use had to occur within 6 days of exposure to chemotherapy and without any subsequent chemotherapy within 14 days after G-CSF use. Febrile neutropenia requiring hospitalization was defined as hospitalization within 14 days after G-CSF use with (a) diagnosis of infection and/or neutropenia (broad definition) or (b) infection and neutropenia diagnoses (narrow definition). Serious adverse drug events (spleen rupture, acute respiratory syndrome, serious allergic reactions, capillary leak syndrome, thrombocytopenia, leukocytosis, cutaneous vasculitis, or bones and muscle ache) were also identified within 14 days after G-CSF use. An incidence difference of < 1% with 90% CI crossing zero qualified as support for noninferiority. Two-tailed chi-square tests were also used to investigate differences. RESULTS: A total of 88 filgrastim and 101 filgrastim-sndz patients were identified. Filgrastim and filgrastim-sndz met the criteria for noninferiority based on an incidence difference of -0.6% (90% CI = -5.1%-4.0%; P = 0.84) for the broad definition of febrile neutropenia and a difference of -0.8% (90% CI = -3.8%-2.1%; P = 0.64) for the narrow definition. For the analysis of serious adverse events, an incidence difference of -2.5% (90% CI = -7.5%-2.5%; P = 0.42) for filgrastim compared with filgrastim-sndz was not sufficient to establish noninferiority. CONCLUSIONS: This study is one of the first analyses of real-world evidence regarding the noninferiority of filgrastim and filgrastim-sndz. The study results support noninferiority of filgrastim and filgrastim-sndz for prevention of febrile neutropenia requiring hospitalization. While noninferiority for serious adverse events was not supported, there was also no statistically significant difference between filgrastim and filgrastim-sndz. The study's small sample size could have limited the analysis of the relatively rare outcomes of febrile neutropenia requiring hospitalization and serious adverse events. A study including a larger numbers of patients taking filgrastim or filgrastim-sndz could provide additional insights. DISCLOSURES: This study received no outside funding. Douglas, Kennedy, and Slabaugh were employees of Humana Pharmacy Solutions at the time the study was conducted. Bowe, Schwab, and Lane were employees of Comprehensive Health Insights, a wholly owned subsidiary of Humana, at the time the study was conducted. Study concept and design were contributed by Douglas, Kennedy, Schwab, and Lane, along with Slabaugh and Bowe. Bowe took the lead in data collection, assisted by Schwab, and data interpretation was performed by Schwab, along with the other authors. The manuscript was written by Schwab, Lane, and Douglas and revised by Kennedy, Slabaugh, and Bowe, along with Schwab, Lane, and Douglas.


Asunto(s)
Biosimilares Farmacéuticos/administración & dosificación , Neutropenia Febril Inducida por Quimioterapia/prevención & control , Filgrastim/administración & dosificación , Fármacos Hematológicos/administración & dosificación , Adulto , Anciano , Anciano de 80 o más Años , Antineoplásicos/administración & dosificación , Antineoplásicos/efectos adversos , Biosimilares Farmacéuticos/efectos adversos , Neutropenia Febril Inducida por Quimioterapia/epidemiología , Estudios de Cohortes , Femenino , Filgrastim/efectos adversos , Fármacos Hematológicos/efectos adversos , Hospitalización/estadística & datos numéricos , Humanos , Incidencia , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Factores de Tiempo , Adulto Joven
6.
Otolaryngol Head Neck Surg ; 155(1): 155-9, 2016 07.
Artículo en Inglés | MEDLINE | ID: mdl-26932964

RESUMEN

OBJECTIVES: To review the management and outcomes of pediatric patients treated for descending mediastinitis at a single institution and contribute to an updated mortality rate. STUDY DESIGN: Case series with chart review. SETTING: Tertiary care pediatric hospital. SUBJECTS AND METHODS: This study is a 19-patient case series of all patients treated for descending mediastinitis at a tertiary pediatric hospital from 1997 to 2015, and it serves as an update to the case series published from this institution in 2008. Review of management included time to diagnosis, time to surgery, surgical procedures performed, and antibiotics administered. The primary outcomes measured were length of hospitalization and mortality. RESULTS: In addition to 8 previously reported patients, we identified 11 pediatric patients treated for descending mediastinitis in the period of review. All 19 patients were <18 months old, and all survived their hospitalization. Fourteen patients underwent surgical drainage at least twice. The median length of hospital stay was 15 days. Retropharyngeal abscess was the source of infection in 16 of 19 patients, and methicillin-resistant Staphylococcus aureus (MRSA) was the isolated organism in 14 of 15 positive cultures. CONCLUSION: This review represents the largest reported series of pediatric patients with descending mediastinitis. With 100% survival, our results suggest that pediatric descending mediastinitis can be safely managed by prompt surgical drainage. Broad-spectrum antibiotics covering MRSA and a low threshold for repeat surgical intervention have been an important part of our successful approach and may decrease length of stay.


Asunto(s)
Mediastinitis/terapia , Antibacterianos/uso terapéutico , Terapia Combinada , Drenaje , Femenino , Humanos , Lactante , Tiempo de Internación/estadística & datos numéricos , Masculino , Mediastinitis/diagnóstico por imagen , Mediastinitis/microbiología , Mediastinitis/mortalidad , Reoperación/estadística & datos numéricos , Estudios Retrospectivos , Tasa de Supervivencia , Tennessee/epidemiología , Tomografía Computarizada por Rayos X , Resultado del Tratamiento
7.
J Trauma Acute Care Surg ; 78(3): 573-9, 2015 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25710429

RESUMEN

BACKGROUND: Oxidative stress associated with hemorrhagic shock and reperfusion (HSR) results in the production of superoxide radicals and other reactive oxygen species, leading to cell damage and multiple-organ dysfunction. We sought to determine if MitoQ, a mitochondria-targeted antioxidant, reduces morbidity in a rat model of HSR by limiting oxidative stress. METHODS: HSR was achieved in male rats by arterial blood withdrawal to a mean arterial pressure of 25 ± 2 mm Hg for 1 hour before resuscitation. MitoQ (5 mg/kg), TPP (triphenylphosphonium, 5 mg/kg) or saline (0.9% vol./vol.) was administered intravenously 30 minutes before resuscitation, followed by an intraperitoneal administration (MitoQ, 20 mg/kg) immediately after resuscitation (n = 5 per group). Morbidity was assessed based on cumulative markers of animal distress (0-10 scale). Rats were sacrificed 2 hours after procedure completion, and liver tissue was collected and processed for histology or assayed for lipid peroxidation (thiobarbituric acid reactive substance [TBARS]) or endogenous antioxidant (catalase, glutathione peroxidase [GPx], and superoxide dismutase) activity. RESULTS: HSR significantly increased morbidity as well as TBARS and catalase activities versus sham. Conversely, no difference in GPx or superoxide dismutase activity was measured between sham, HSR, and TPP, MitoQ administration reduced morbidity versus HSR (5.8 ± 0.3 vs. 7.6 ± 0.3; p < 0.05), while TPP administration significantly reduced hepatic necrosis versus both HSR and HSR-MitoQ (1.2 ± 0.1 vs. 2.0 ± 0.2 vs. 1.9 ± 0.2; p < 0.05, n = 5). Analysis of oxidative stress demonstrated increased TBARS and GPx in HSR-MitoQ versus sham (12.0 ± 1.1 µM vs. 6.2 ± 0.5 µM and 37.9 ± 3.0 µmol/min/mL vs. 22.9 ± 2.7 µmol/min/mL, TBARS and GPx, respectively, n = 5; p < 0.05). Conversely, catalase activity in HSR-MitoQ was reduced versus HSR (1.96 ± 1.17 mol/min/mL vs. 2.58 ± 1.81 mol/min/mL; n = 5; p < 0.05). Finally, MitoQ treatment decreased tumor necrosis factor α (0.66 ± 0.07 pg/mL vs. 0.92 ± 0.08 pg/mL) and interleukin 6 (7.3 ± 0.8 pg/mL vs. 11 ± 0.9 pg/mL) versus HSR as did TPP alone (0.58 ± 0.05 pg/mL vs. 0.92 ± 0.08 pg/mL; 6.7 ± 0.6 pg/mL vs. 11 ± 0.9 pg/mL; n = 5; p < 0.05). CONCLUSION: Our data demonstrate that MitoQ treatment following hemorrhage significantly limits morbidity and decreases hepatic tumor necrosis factor α and interleukin 6. In addition, MitoQ differentially modulates oxidative stress and hepatic antioxidant activity.


Asunto(s)
Hemorragia/complicaciones , Compuestos Organofosforados/farmacología , Estrés Oxidativo/efectos de los fármacos , Ubiquinona/análogos & derivados , Animales , Antioxidantes/metabolismo , Catalasa/metabolismo , Ensayo de Inmunoadsorción Enzimática , Inmunohistoquímica , Inflamación/prevención & control , Peroxidación de Lípido , Hígado/metabolismo , Hígado/patología , Masculino , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Resucitación/métodos , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismo , Ubiquinona/farmacología
8.
J Trauma Acute Care Surg ; 76(2): 409-17, 2014 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-24458046

RESUMEN

BACKGROUND: Oxidative stress following hemorrhagic shock and resuscitation (HSR) is regulated, in part, by inflammatory and apoptotic mediators such as necrosis factor κB (NF-κB) and p53. Sirtuin 1 (Sirt-1) is a metabolic intermediary that regulates stress responses by suppressing NF-κB and p53 activity. Resveratrol is a naturally occurring polyphenolic antioxidant and Sirt-1 agonist. The aim of this study was to determine whether resveratrol protects hepatocytes following HSR or hypoxia. METHODS: In vivo, HSR was achieved in male rats by arterial blood withdrawal to 30 ± 2 mm Hg for 1 hour before resuscitation with or without resveratrol (Res, 30 mg/kg). Hepatic tissue was stained and scored for necrosis, interleukin 6, and Sirt-1 expression. In vitro, primary rat hepatocytes were subjected to 8 hours of hypoxia without or with Res (100 µM). Cells were analyzed immediately or after 6 hours of normoxia, for survival and markers of injury (lactate dehydrogenase assay, lipid peroxidation, and mitochondrial integrity). Cell lysates were collected for cytochrome c analysis and immunoprecipitated using antibodies against NF-κB (p65) or p53. RESULTS: In vivo, animals subject to HSR exhibited increased expression of markers of hepatocyte damage compared with those sham operated, concomitant with lower Sirt-1 expression. In vitro, hypoxia followed by normoxia resulted in increased cell death, an effect that was blunted by Res. Analysis of cell and mitochondrial function demonstrated that Res inhibited the detrimental effects of hypoxia in isolated hepatocytes. CONCLUSION: Resveratrol prevents cell death in HSR and exerts a protective effect on the mitochondria in a hepatocyte model of hypoxic injury-reoxygenation possibly via Sirt-1 modulation of p53 and NF-κB activity.


Asunto(s)
Hepatocitos/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Resucitación/métodos , Choque Hemorrágico/terapia , Estilbenos/farmacología , Animales , Western Blotting , Muerte Celular/efectos de los fármacos , Hipoxia de la Célula/efectos de los fármacos , Supervivencia Celular , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática , Hepatocitos/metabolismo , Inmunohistoquímica , Técnicas In Vitro , Interleucina-6/análisis , Interleucina-6/metabolismo , Masculino , Mitocondrias Hepáticas/metabolismo , FN-kappa B/metabolismo , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Valores de Referencia , Resveratrol , Choque Hemorrágico/mortalidad , Choque Hemorrágico/fisiopatología , Sirtuina 1/efectos de los fármacos , Sirtuina 1/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo
9.
Opt Express ; 20(17): 18925-30, 2012 Aug 13.
Artículo en Inglés | MEDLINE | ID: mdl-23038531

RESUMEN

We report measurements which give direct insight into the origins of the transparency current for λ ~5 µm In0.6Ga0.4As/In0.42Al0.58As quantum cascade lasers in the temperature range of 80-280 K. The transparency current values have been found from broadband transmission measurements through the laser waveguides under sub-threshold operating conditions. Two active region designs were compared. The active region of the first laser is based on double-LO-phonon relaxation approach, while the second device has only one lower level, without specially designed resonant LO-phonon assisted depopulation. It is shown that transparency current contributes more than 70% to the magnitude of threshold current at high temperatures for both designs.


Asunto(s)
Rayos Láser , Espectrofotometría Infrarroja/instrumentación , Resonancia por Plasmón de Superficie/instrumentación , Diseño Asistido por Computadora , Diseño de Equipo , Análisis de Falla de Equipo , Rayos Infrarrojos , Teoría Cuántica
10.
Orthopedics ; 34(12): 982-5, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-22147215

RESUMEN

Metastases to the bone are a frequent complication of advanced cancer. Bone metastases have been linked to skeletal-related events, which is the composite endpoint used in clinical trials evaluating therapy to minimize these complications. This article discusses bisphosphonates, which are the historical standard for the prevention of skeletal-related events in patients with metastases from solid tumors and multiple myeloma, and denosumab, which is the first Food and Drug Administration-approved receptor activator of nuclear factor kappa-ß ligand (RANKL) inhibitor.


Asunto(s)
Anticuerpos Monoclonales/uso terapéutico , Conservadores de la Densidad Ósea/uso terapéutico , Neoplasias Óseas/tratamiento farmacológico , Difosfonatos/uso terapéutico , Mieloma Múltiple/tratamiento farmacológico , Anticuerpos Monoclonales/economía , Anticuerpos Monoclonales Humanizados , Neoplasias Óseas/secundario , Denosumab , Difosfonatos/economía , Humanos , Mieloma Múltiple/secundario , Honorarios por Prescripción de Medicamentos , Ligando RANK/antagonistas & inhibidores
11.
Cardiovasc Hematol Agents Med Chem ; 9(4): 262-8, 2011 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21902659

RESUMEN

STUDY OBJECTIVE: To evaluate the effectiveness of our institutions heparin-induced thrombocytopenia (HIT) protocol in achieving a therapeutic activated partial thromboplastin time (aPTT) and to evaluate patient outcomes related to bleeding and thrombotic events before and after protocol implementation. DESIGN: Retrospective, single-center, pre- and post- assessment of a protocol previously approved at our institution. SETTING: 400-bed community hospital serving surrounding rural populations with emphasis in cardiothoracic surgery. PATIENTS: Retrospective chart review based on drug charge data identified 29 patients that received either argatroban or lepirudin for greater than 24 hours. Nineteen patients received either argatroban or lepirudin prior to HIT-protocol implementation, while the remaining ten received either drug after the HIT protocol was implemented. INTERVENTION: Implementation of HIT protocol occurred in March 2009. Patients were divided into pre-protocol and post-protocol groups. RESULTS: Primary outcome was to evaluate the number of therapeutic, subtherapeutic, and supratherapeutic aPTTs between two groups. In the pre-protocol group, aPTTs were therapeutic, subtherapeutic, and supratherapeutic 48.5% (164/338), 14.2% (48/338), and 37.2% (126/338) of the time, respectively. Meanwhile aPTTs in the post-protocol group were therapeutic, subtherapeutic, and supratherapeutic 46.6% (89/191), 22% (42/191), and 31.4% (60/191) of the time, respectively. The number of subtherapeutic aPTTs was statistically higher in the post-protocol group compared to the pre-protocol group. Secondary endpoints included the number of bleeding events and number of thrombotic events. None of the secondary endpoints reached statistical significance. Time to therapeutic aPTT was also evaluated: in the pre-protocol group median time (range) was 15 hours (2-108.6) compared to 8.1 hours (2.3-94.2) in the post-protocol group. CONCLUSIONS: Adoption and implementation of HIT protocol at our institution resulted in significantly more subtherapeutic aPTTs as compared to time prior to protocol. Although not statistically significant, the time required to obtain therapeutic aPTT was reduced by almost 50% after protocol implementation, which could be of clinical importance. Larger studies are needed to continue to assess if standardized protocols are effective in treatment of HIT.


Asunto(s)
Anticoagulantes/efectos adversos , Antitrombinas/uso terapéutico , Heparina/efectos adversos , Ácidos Pipecólicos/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Trombocitopenia/inducido químicamente , Trombocitopenia/tratamiento farmacológico , Anciano , Arginina/análogos & derivados , Femenino , Hirudinas , Humanos , Masculino , Persona de Mediana Edad , Tiempo de Tromboplastina Parcial , Proteínas Recombinantes/uso terapéutico , Sulfonamidas , Resultado del Tratamiento
12.
Am J Phys Anthropol ; 121(2): 112-6, 2003 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-12740954

RESUMEN

Recovery of ancient DNA has become an increasingly important tool in elucidating the origins of past populations and their relationships. Unfortunately, many human skeletal remains do not contain original DNA amplifiable by polymerase chain reaction (PCR). Amino-acid racemization has proven to be a useful predictor of ancient DNA results. We analyzed the relative levels of amino-acid preservation and racemization of human samples from two highland dry-cave sites in Sri Lanka, and found that amino-acid enantiomer ratios were inconsistent with successful authentic DNA recovery. A review of the literature reveals that these results are consistent with a global pattern of poor DNA preservation in the tropics.


Asunto(s)
Arqueología/métodos , ADN/análisis , ADN/historia , Microclima , Preservación Biológica , Aminoácidos/análisis , Historia Antigua , Humanos , Sri Lanka , Clima Tropical
13.
J Air Waste Manag Assoc ; 46(2): 148-158, 1996 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28081416

RESUMEN

The purpose of this study was to intercompare hydrocarbon (HC) measurements performed by a number of different instruments: a gas chromatograph (GC), a flame ionization detector (FID), a fourier transform infrared spectrometer (FTIR), a commercially produced non-dispersive infrared analyzer (NDIR), and two remote sensors. These instruments were used to measure total HC concentrations in a variety of samples, including (1) ten different individual HC species, (2) 12 different vehicle exhaust samples, and (3) three different volatilized fuel samples. The 12 exhaust samples were generated by operating two different vehicles on a dynamometer. Each vehicle was operated at different times with three different fuels. The vehicles were operated fuel rich, i.e., with low air/fuel ratios to encourage elevated exhaust HC levels. Some of the exhaust samples were obtained while operating each vehicle at a stoichiometric air/fuel ratio with one spark plug wire disconnected. To quantify the degree to which the various instruments agreed with the FID, a parameter called the response factor was used, where the response factor was defined as the HC/CO2 ratio measured by each instrument divided by the HC/CO2 ratio measured by the dynamometer bench. Of the various instruments, only the GC yielded response factors that were consistently at or close to one. The other instruments typically had values at or below one. For the ten individual HC species studied, the NDIR and remote sensors obtained response factors between 0.05 and 1.0, with the highest response factors being obtained for the alkanes and the lowest response factors obtained for toluene and ethylene. For the exhaust samples, the NDIR and remote sensors obtained response factors between 0.23 and 0.68. For raw fuel samples, the response factors were between 0.44 and 0.68. NDIR and remote sensor measurements correlated very poorly with total HC in exhaust.

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