Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 51
Filtrar
Más filtros

Bases de datos
Tipo del documento
Intervalo de año de publicación
1.
Nature ; 561(7722): 206-210, 2018 09.
Artículo en Inglés | MEDLINE | ID: mdl-30209369

RESUMEN

Earth and its magnetosphere are immersed in the supersonic flow of the solar-wind plasma that fills interplanetary space. As the solar wind slows and deflects to flow around Earth, or any other obstacle, a 'bow shock' forms within the flow. Under almost all solar-wind conditions, planetary bow shocks such as Earth's are collisionless, supercritical shocks, meaning that they reflect and accelerate a fraction of the incident solar-wind ions as an energy dissipation mechanism1,2, which results in the formation of a region called the ion foreshock3. In the foreshock, large-scale, transient phenomena can develop, such as 'hot flow anomalies'4-9, which are concentrations of shock-reflected, suprathermal ions that are channelled and accumulated along certain structures in the upstream magnetic field. Hot flow anomalies evolve explosively, often resulting in the formation of new shocks along their upstream edges5,10, and potentially contribute to particle acceleration11-13, but there have hitherto been no observations to constrain this acceleration or to confirm the underlying mechanism. Here we report observations of a hot flow anomaly accelerating solar-wind ions from roughly 1-10 kiloelectronvolts up to almost 1,000 kiloelectronvolts. The acceleration mechanism depends on the mass and charge state of the ions and is consistent with first-order Fermi acceleration14,15. The acceleration that we observe results from only the interaction of Earth's bow shock with the solar wind, but produces a much, much larger number of energetic particles compared to what would typically be produced in the foreshock from acceleration at the bow shock. Such autogenous and efficient acceleration at quasi-parallel bow shocks (the normal direction of which are within about 45 degrees of the interplanetary magnetic field direction) provides a potential solution to Fermi's 'injection problem', which requires an as-yet-unexplained seed population of energetic particles, and implies that foreshock transients may be important in the generation of cosmic rays at astrophysical shocks throughout the cosmos.

2.
Subst Use Misuse ; 59(7): 1031-1038, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38403989

RESUMEN

INTRODUCTION: Although Indian Americans constitute the second-largest immigrant group in the United States, there is a paucity of information about Indian American youth, particularly with respect to substance use risk. We examined the relationship of social factors to permissive substance use beliefs (a proxy for substance use risk since they can lead to adulthood substance use and misuse) and family functioning. METHODS: The study used structural equation modeling to examine the prevalence of permissive substance use beliefs in a sample of Indian American youth ages 12-17 (N = 223) and examined the degree to which discrimination, bicultural identity integration, and endorsement of the model minority stereotype were associated with permissive substance use beliefs. RESULTS: Findings suggest that bicultural identity integration (B = 0.267 [SE = 0.112], p = 0.01) and discrimination (B = 0.294 [SE = 0.087], p = 0.001) are positively associated with permissive substance use beliefs. Bicultural identity integration (B = 0.415 [SE = 0.090], p = 0.0001) was positively associated with family support (B= -0.329 [SE = 0.108], p = 0.002) which, in turn, was associated with less permissive substance use beliefs. In contrast, endorsement of the model minority stereotype (B = 0.351 [SE = 0.090], p = 0.001) was positively associated with family closeness (B = 0.232 [SE = 0.927], p = 0.01) which, in turn, was associated with family support and then with less permissive substance use beliefs. CONCLUSIONS: Discrimination and bicultural identity integration emerged as key constructs related to substance use risk among Indian American youth. These youth could benefit from culturally appropriate prevention programming that addresses the negative impact of discrimination and its effect on permissive substance use beliefs and highlights protective factors.


Asunto(s)
Conducta del Adolescente , Trastornos Relacionados con Sustancias , Adolescente , Humanos , Grupos Minoritarios , Factores de Riesgo , Trastornos Relacionados con Sustancias/prevención & control , Estados Unidos/epidemiología , Asiático , Cultura , Niño , Apoyo Familiar
3.
Soc Psychiatry Psychiatr Epidemiol ; 58(7): 1075-1085, 2023 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-36564584

RESUMEN

PURPOSE: Rooted in a trans-territorial framework, the present study was designed to provide new evidence regarding the patterns of communication among Hurricane Maria survivors who migrated to the U.S. in the aftermath of the storm. METHODS: A total of 319 Hurricane Maria survivor adults ages 18 and older were recruited into the Adelante Boricua study between August 2020 and October 2021. Most participants had relocated to the U.S. between 2017 and 2018. We used latent profile analysis and multinomial regression to examine the relationship of technology-based communication with depressive symptoms, well-being, cultural connection, and migration stress. RESULTS: We identified a five-class solution, consisting of (1) moderate communication (32%), (2) disengaged (24%), (3) no social media (18%), (4) daily with family in Puerto Rico (6%), and (5) daily trans-territorial (13%) typologies. Participants in the disengaged class were more likely to report elevated depressive symptoms and limited English proficiency, lower prosocial behaviors, lower levels of religiosity, lower attendance at religious services in the U.S., and less engagement in social activities, compared to participants in the Moderate Communication class. CONCLUSION: Roughly one in four individuals in our sample reported very limited technology-based communication with friends/family in their sending and new-receiving communities. As technology and smartphones continue to become integrated into 21st-century life, it is vital that researchers explore how the tremendous potential for connectedness relates to trans-territorial crisis migrants' well-being and adaptation.


Asunto(s)
Tormentas Ciclónicas , Migrantes , Adulto , Estados Unidos , Humanos , Puerto Rico
4.
Geophys Res Lett ; 45(10): 4569-4577, 2018 May 28.
Artículo en Inglés | MEDLINE | ID: mdl-31031447

RESUMEN

Magnetospheric Multiscale observations are used to probe the structure and temperature profile of a guide field reconnection exhaust ~100 ion inertial lengths downstream from the X-line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near 1 edge of the exhaust and containing electron flow toward the X-line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust, but within the cavity, electron cooling and enhanced parallel ion heating were found. This is explained in terms of the parallel electric field, which inhibits electron mixing within the cavity on newly reconnected field lines but accelerates ions. Consequently, guide field reconnection causes inhomogeneous changes in ion and electron temperature across the exhaust.

5.
Phys Rev Lett ; 117(16): 165101, 2016 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-27792387

RESUMEN

Collisionless shock nonstationarity arising from microscale physics influences shock structure and particle acceleration mechanisms. Nonstationarity has been difficult to quantify due to the small spatial and temporal scales. We use the closely spaced (subgyroscale), high-time-resolution measurements from one rapid crossing of Earth's quasiperpendicular bow shock by the Magnetospheric Multiscale (MMS) spacecraft to compare competing nonstationarity processes. Using MMS's high-cadence kinetic plasma measurements, we show that the shock exhibits nonstationarity in the form of ripples.

6.
Phys Rev Lett ; 117(1): 015001, 2016 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-27419573

RESUMEN

We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E_{∥}) that is larger than predicted by simulations. The high-speed (∼300 km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E_{∥} is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

7.
Phys Rev Lett ; 116(23): 235102, 2016 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-27341241

RESUMEN

We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E_{∥}) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E_{∥} events near the electron diffusion region have amplitudes on the order of 100 mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E_{∥} events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E_{∥} events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

8.
Georgian Med News ; (244-245): 45-55, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26177135

RESUMEN

In the present study we sought to clarify links between religious exclusivity, as form of intergroup favoritism, and indices of psychosocial functioning. The study of in group favoritism has generally been invoked within Social Identity Theory and related perspectives. However, there is a lack of literature regarding religious exclusivity from the standpoint of social identity. In particular, the ways in which religious exclusivity is linked with other dimensions of religious belief and practice, and with psychosocial functioning, among individuals from different religious backgrounds are not well understood. A sample of 8545 emerging-adult students from 30 U.S. universities completed special measures. Measure of religious exclusivity was developed and validated for this group. The results suggest that exclusivity appears as predictor for impaired psychosocial functioning, low self-esteem and low psychosocial well-being for individuals from organized faiths, as well as for those identifying as agnostic, atheist, or spiritual/nonreligious. These findings are discussed in terms of Social Identity Theory and Terror Management Theory (TMT).


Asunto(s)
Cristianismo/psicología , Religión y Psicología , Identificación Social , Adulto , Femenino , Humanos , Masculino , Estudiantes , Estados Unidos , Universidades
9.
Sleep Breath ; 17(1): 351-63, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-22528953

RESUMEN

PURPOSE: There are little existing data on continuous positive airway pressure (CPAP) adherence in US Hispanic veterans with obstructive sleep apnea (OSA). Our aim was to describe determinants of 1-month adherence in a sleep clinic cohort of South Florida Hispanic veterans. METHODS: Hispanic veterans referred to the Miami VA sleep clinic were recruited and completed questionnaires about sleep apnea risk, sleep quality, insomnia symptoms, sleepiness, depression/anxiety, acculturation, personality traits, and cognitions about OSA and CPAP. Individuals at risk for OSA were scheduled for baseline polysomnography (PSG), followed by in-lab CPAP titration or a trial of auto-CPAP. Participants with OSA accepting CPAP therapy were asked to return after 7 and 30 days of treatment for adherence verification and to repeat questionnaires. RESULTS: One hundred twenty-four participants (94 % men) were enrolled with 114 completing overnight PSG. Eighty-six out of 95 participants (91 %) with sleep apnea syndrome or moderate to severe OSA accepted CPAP treatment. Fifty-nine participants completed both follow-up visits with a mean CPAP use at 30 days of 3.6 ± 2.0 h. The only independent predictor of 7-day mean daily CPAP use was the baseline Insomnia Severity Index while the best predictor of 30-day mean daily CPAP use was the 7-day mean daily use. CONCLUSIONS: Our study suggests that South Florida Hispanic veterans with OSA evaluated in a sleep clinic show poor CPAP adherence. Insomnia and poor early use predicted poor adherence overall. Larger prospective studies with other race-ethnic groups are needed to determine the role of ethnicity and race in CPAP adherence among US veterans with OSA.


Asunto(s)
Presión de las Vías Aéreas Positiva Contínua/psicología , Hispánicos o Latinos/etnología , Hispánicos o Latinos/psicología , Apnea Obstructiva del Sueño/etnología , Apnea Obstructiva del Sueño/terapia , Veteranos/psicología , Aculturación , Adulto , Instituciones de Atención Ambulatoria , Estudios de Cohortes , Comorbilidad , Femenino , Florida , Humanos , Masculino , Persona de Mediana Edad , Polisomnografía/psicología , Apnea Obstructiva del Sueño/psicología
10.
Phys Rev Lett ; 108(2): 025002, 2012 Jan 13.
Artículo en Inglés | MEDLINE | ID: mdl-22324692

RESUMEN

Whistler wave trains are observed in the foot region of high Mach number quasiperpendicular shocks. The waves are oblique with respect to the ambient magnetic field as well as the shock normal. The Poynting flux of the waves is directed upstream in the shock normal frame starting from the ramp of the shock. This suggests that the waves are an integral part of the shock structure with the dispersive shock as the source of the waves. These observations lead to the conclusion that the shock ramp structure of supercritical high Mach number shocks is formed as a balance of dispersion and nonlinearity.

11.
Phys Rev Lett ; 103(16): 165003, 2009 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-19905703

RESUMEN

To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorov's law approximately k(-5/3) at MHD scales, a approximately k(-2.8) power law at ion scales, and an exponential approximately exp[-sqrt[k(rho)e]] at scales k(rho)e approximately [0.1,1], where rho(e) is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence.

12.
Food Chem ; 237: 685-692, 2017 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-28764053

RESUMEN

Food processing alters the physicochemical state of soy which can enhance chemical and enzymatic conversion of isoflavones to their aglycone forms. This study investigated the role of ß-glycosidase from processed soy-ingredient mixture (SIM) or almonds, and examined the impact of isoflavone composition in mediating conversion to aglycones. ß-Glycosidase activity was quantified using p-nitrophenol-ß-d-glucopyranoside and SIM isoflavone extracts. Almond ß-glycosidase activity was significantly (p<0.001) reduced after roasting (99% reduction) or steaming (97% reduction) compared to raw almonds. SIM ß-glycosidase activity, however, increased, with steaming by 66% (p<0.001) and with roasting by 52% (p=0.022), compared to raw SIM. After incubation with ß-glycosidase, percentage of aglycone (total aglycone/total isoflavones) in SIM isoflavone extracts increased significantly in raw (35%), fermented (48%), roasted (88%) and steamed (91%) SIM, compared to their initial (∼5%) compositions. Manipulation of ß-glycosidase activity and isoflavone composition can be used to modulate aglycone content in soy food products.


Asunto(s)
Glicósido Hidrolasas/metabolismo , Glicósidos/metabolismo , Prunus dulcis , Isoflavonas , Nitrofenoles
13.
Aliment Pharmacol Ther ; 46(3): 303-309, 2017 08.
Artículo en Inglés | MEDLINE | ID: mdl-28524546

RESUMEN

BACKGROUND: Despite a rising incidence of inflammatory bowel disease (IBD) in Hispanics in the United States, there are no studies examining the relationship between immigrant generation and IBD onset among Hispanics. AIMS: To determine whether age of IBD diagnosis, time from immigration to IBD diagnosis and IBD phenotype, differed across immigration periods in South Florida Cuban immigrants. METHODS: This was a cohort of consecutively identified Cuban-born adults who developed IBD in the United States and were followed in gastroenterology (GI) clinic. We divided time cohorts of immigration by historical relevance: before 1980, 1980-1994 and 1995-to-present. We examined differences across time cohorts in diagnosis age, time from immigration to IBD diagnosis, and IBD phenotype (ie, IBD type, disease location). RESULTS: A total of 130 Cuban patients with IBD were included. Age of IBD diagnosis was older in Cubans arriving before 1980 than in those arriving between 1980-1994 or after 1995 (44.7 vs 33.79 and 33.71, respectively, P<.0001). Time between immigration and diagnosis was shorter in patients arriving to the US after 1980 (31.77 years, Standard deviation (SD) 12.83 (<1980) vs 17.13 years, SD 8.55 (1980-1994) and 8.30 years, SD 4.72 (1995-to-present). IBD phenotype, including type of IBD, disease location and surgeries, did not differ significantly across time cohorts. CONCLUSIONS: Our study describes changing patterns of IBD onset following immigration in Cubans, suggesting that environmental changes either in the United States, Cuba or both are resulting in faster IBD onset in younger immigrant generations. These studies can inform the search for environmental triggers that may result in IBD.


Asunto(s)
Emigrantes e Inmigrantes/estadística & datos numéricos , Hispánicos o Latinos/estadística & datos numéricos , Enfermedades Inflamatorias del Intestino/epidemiología , Adulto , Anciano , Estudios de Cohortes , Cuba/etnología , Emigración e Inmigración , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Estados Unidos/epidemiología , Adulto Joven
14.
Cancer Epidemiol Biomarkers Prev ; 5(10): 823-33, 1996 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-8896894

RESUMEN

An evaluation of the Health Professionals Follow-Up Study has detected a lower prostate cancer risk associated with the greater consumption of tomatoes and related food products. Tomatoes are the primary dietary source of lycopene, a non-provitamin A carotenoid with potent antioxidant activity. Our goal was to define the concentrations of lycopene, other carotenoids, and retinol in paired benign and malignant prostate tissue from 25 men, ages 53 to 74, undergoing prostatectomy for localized prostate cancer. The concentrations of specific carotenoids in the benign and malignant prostate tissue from the same subject are highly correlated. Lycopene and all-trans beta-carotene are the predominant carotenoids observed, with means +/- SE of 0.80 +/- 0.08 nmol/g and 0.54 +/- 0.09, respectively. Lycopene concentrations range from 0 to 2.58 nmol/g, and all-trans beta-carotene concentrations range from 0.09 to 1.70 nmol/g. The 9-cis beta-carotene isomer, alpha-carotene, lutein, alpha-cryptoxanthin, zeaxanthin, and beta-cryptoxanthin are consistently detectable in prostate tissue. No significant correlations between the concentration of lycopene and the concentrations of any other carotenoid are observed. In contrast, strong correlations between prostate beta-carotene and alpha-carotene are noted (correlation coefficient, 0.88; P < 0.0001), as are correlations between several other carotenoid pairs, which reflects their similar dietary origins. Mean vitamin A concentration in the prostate is 1.52 nmol/g, with a range of 0.71 to 3.30 nmol/g. We further evaluated tomato-based food products, serum, and prostate tissue for the presence of geometric lycopene isomers using high-performance liquid chromatography with a polymeric C30 reversed phase column. All-trans lycopene accounts for 79 to 91% and cis lycopene isomers for 9 to 21% of total lycopene in tomatoes, tomato paste, and tomato soup. Lycopene concentrations in the serum of men range between 0.60 and 1.9 nmol/ml, with 27 to 42% all-trans lycopene and 58 to 73% cis-isomers distributed among 12 to 13 peaks, depending upon their chromatographic resolution. In striking contrast with foods, all-trans lycopene accounts for only 12 to 21% and cis isomers for 79 to 88% of total lycopene in benign or malignant prostate tissues. cis Isomers of lycopene within the prostate are distributed among 14 to 18 peaks. We conclude that a diverse array of carotenoids are found in the human prostate with significant intra-individual variation. The presence of lycopene in the prostate at concentrations that are biologically active in laboratory studies supports the hypothesis that lycopene may have direct effects within the prostate and contribute to the reduced prostate cancer risk associated with the reduced prostate cancer risk associated with the consumption of tomato-based foods. The future identification and characterization of geometric lycopene isomers may lead to the development of novel agents for chemoprevention studies.


Asunto(s)
Anticarcinógenos/análisis , Antioxidantes/análisis , Biomarcadores/química , Próstata/química , Neoplasias de la Próstata/química , Anciano , Carotenoides/análisis , Cromatografía Líquida de Alta Presión , Dieta , Humanos , Licopeno , Masculino , Persona de Mediana Edad , Neoplasias de la Próstata/epidemiología , Factores de Riesgo , Vitamina A/análisis , beta Caroteno/análisis
15.
J Thorac Cardiovasc Surg ; 101(6): 989-97, 1991 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-2038208

RESUMEN

Intravascular techniques were used to extract 226 leads from 124 patients. Indications for lead extraction were life-threatening septicemia (30%), complications of free-floating leads (2%), abandonment of pockets (40%), and replacement of malfunctioning leads (28%). Extraction tools included flexible, telescoping sheaths advanced over the lead to dilate scar tissue and apply countertraction, deflection catheters, and wire basket snares. Countertraction is defined as the direct force of traction on the lead countered by the circumference of an extraction sheath. One hundred sixty-four leads were extracted through the superior vena cava by advancing the sheaths over the lead to the myocardial wall. Most of these leads passed through the subclavian vein. An approach through the inferior vena cava was used for the remaining 62 leads. The countertraction sheaths were passed from the femoral vein into the right atrium. A maneuvering catheter and an extracting snare were placed inside the sheaths. The lead was positioned by the maneuvering catheter, entangled in the extracting snare, and the sheaths advanced over the snare and lead to the myocardium. An atriotomy by means of a limited surgical approach was required to free one lead. One infected lead broke 5 cm from the electrode and was removed through a median sternotomy, ventriculotomy, and retrograde extraction. All patients had unremarkable recoveries. Intravascular countertraction techniques proved to be a viable alternative, minimizing the risks and morbidity of lead removal.


Asunto(s)
Marcapaso Artificial , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Cardiología/instrumentación , Cateterismo/instrumentación , Niño , Femenino , Humanos , Masculino , Métodos , Persona de Mediana Edad
16.
J Thorac Cardiovasc Surg ; 89(1): 142-4, 1985 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-3965811

RESUMEN

When a pacing lead becomes infected, the most expedient and successful therapy is its removal. A new surgical extraction technique, combining the use of fluoroscopy and a limited surgical dissection of the right atrium, is presented for the removal of a lead entrapped in the heart or venous system.


Asunto(s)
Cuerpos Extraños/cirugía , Marcapaso Artificial/efectos adversos , Reoperación , Procedimientos Quirúrgicos Operativos , Anciano , Disección/métodos , Electrodos Implantados/efectos adversos , Femenino , Humanos , Masculino
17.
J Chromatogr A ; 719(2): 333-43, 1996 Jan 08.
Artículo en Inglés | MEDLINE | ID: mdl-8581121

RESUMEN

The recent development and application of a polymeric C30 stationary phase have given unique separations of cis-trans carotenoid isomers in reversed-phase (RP) liquid chromatography (LC) owing to the exceptional shape selectivity of this stationary phase. In the present research, several geometrical isomers of alpha-carotene were at least partially resolved from a photo-isomerized mixture when chromatographed on a 3-microns polymeric C30 column. Double bond configurations of the five predominant alpha-carotene peaks, as isolated on a semi-preparative C30 column, were unambiguously assigned using 1H nuclear magnetic resonance (NMR) spectroscopy, giving the following order of elution: 13-cis, 13'-cis, all-trans, 9-cis, and 9'-cis geometrical forms. Electronic absorption spectra for these isomers were in agreement with the identification of peaks. The alpha-carotene isomers separated and identified herein had not been previously resolved in RPLC. Confirmation of the structures of geometrical alpha-carotene isomers will aid further studies on the possible physiological roles of these compounds in biological tissues.


Asunto(s)
Carotenoides/química , Carotenoides/aislamiento & purificación , Cromatografía Liquida/métodos , Isomerismo , Espectroscopía de Resonancia Magnética
18.
Cardiol Clin ; 10(4): 735-48, 1992 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-1423384

RESUMEN

Each of the extraction techniques and their ancillary tools was reported as used successfully; however, until now, no technique has been successful when used in more than a few isolated instances. The technique for intravascular countertraction and the associated tools described in this paper were devised and selected in an attempt to develop one technique to be used on all patients, with all types of leads, and with a very low complication rate. Its versatility permitted single or multiple lead extractions combined with the precision of selecting and extracting a specific lead. In our experience, as well as the experience of others, the techniques described in this paper have proved to be superior by minimizing the inherent risk and morbidity, allowing us to expand the indications for lead removal beyond septicemia and free-floating leads, to include infection, abandonment of pockets, and replacement of malfunctioning or fractured leads. Intravascular countertraction was a consistently safe and efficacious method of removing transvenous pacemaker leads regardless of the duration of the implant, thus permitting extractions in patients not considered candidates for a more extensive surgical procedure. Intravascular countertraction encompasses surgical and fluoroscopic techniques possessed by most physicians experienced in pacemaker and automatic implantable cardioverter defibrillator implants. However, there is a learning curve, predicating caution for the inexperienced physician. In addition, advanced surgical skills may be needed in handling associated conditions such as debridement and primary closure of chronically inflamed tissues, especially in submuscular pockets and sinus tracts in the neck. Although the potential for a cardiovascular complication is small, it does exist, and cardiovascular surgical backup is a recommended precaution.


Asunto(s)
Electrodos Implantados , Endocarditis Bacteriana/terapia , Marcapaso Artificial , Sepsis/terapia , Puente Cardiopulmonar , Falla de Equipo , Ventrículos Cardíacos/cirugía , Humanos , Tracción/instrumentación
19.
J Agric Food Chem ; 47(9): 3558-64, 1999 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-10552685

RESUMEN

Paprika oleoresin was fractionated by extraction with supercritical carbon dioxide (SCF-CO(2)). Higher extraction volumes, increasing extraction pressures, and similarly, the use of cosolvents such as 1% ethanol or acetone resulted in higher pigment yields. Within the 2000-7000 psi range, total oleoresin yield always approached 100%. Pigments isolated at lower pressures consisted almost exclusively of beta-carotene, while pigments obtained at higher pressures contained a greater proportion of red carotenoids (capsorubin, capsanthin, zeaxanthin, beta-cryptoxanthin) and small amounts of beta-carotene. The varying solubility of oil and pigments in SCF-CO(2) was optimized to obtain enriched and concentrated oleoresins through a two-stage extraction at 2000 and 6000 psi. This technique removes the paprika oil and beta-carotene during the first extraction step, allowing for second-stage oleoresin extracts with a high pigment concentration (200% relative to the reference) and a red:yellow pigment ratio of 1.8 (as compared to 1.3 in the reference).


Asunto(s)
Capsicum/química , Extractos Vegetales/aislamiento & purificación , Plantas Medicinales , Dióxido de Carbono , Análisis de los Alimentos/instrumentación , Análisis de los Alimentos/métodos , Presión
20.
J Agric Food Chem ; 49(2): 664-8, 2001 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-11262009

RESUMEN

High-pressure processing (HPP) can inactivate pathogenic microorganisms and degradative enzymes without the use of heat, thereby minimizing the destruction of flavors, nutrients, and other quality attributes. Lipoxygenase plays a role in the off-flavor production of tomatoes, whereas pectinesterase and polygalacturonase impact tomato texture. The purpose of this study was to determine HPP's ability to inactivate lipoxygenase, pectinesterase, and polygalacturonase in diced tomatoes. Processing conditions used were 400, 600, and 800 MPa for 1, 3, and 5 min at 25 and 45 degrees C. The magnitude of applied pressure had a significant effect on inactivating lipoxygenase and polygalacturonase (p < 0.05), with complete loss of activity occurring at 800 MPa. Pectinesterase was very resistant to pressure treatment. Percent soluble solids, pH, titratable acidity, and color a/b values did not differ significantly among the high-pressure-processed samples as compared to the control, but color L values increased. This change in L values was not considered of practical importance. Apparent protein content decreased in the pressure-processed samples, due possibly to protein denaturation, loss of solubility, and/or a decrease in dye binding sites to assay protein content.


Asunto(s)
Hidrolasas de Éster Carboxílico/metabolismo , Lipooxigenasa/metabolismo , Poligalacturonasa/metabolismo , Solanum lycopersicum/enzimología , Manipulación de Alimentos/métodos , Cinética , Presión , Gusto
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA