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1.
Rev Sci Instrum ; 92(12): 121501, 2021 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-34972455

RESUMEN

This work aims to provide details on the latest technological developments regarding LiDAR (Light Imaging Detection And Ranging) systems, with particular reference to the techniques, architectures, and methodologies partially or entirely implemented by means of the FPGA (Field Programmable Gate Array) environment. Currently, LiDAR technology is considered of great interest as it is widely employed in a variety of application fields, such as automotive, seismology, archaeology, metrology, and military. For this reason, the required performances are gradually increasing, which leads to complex and stringent solutions. The growth in LiDAR systems' complexity suggests the use of high-end general-purpose computing units such as central processing units to perform very complex tasks and FPGAs to perform multiple tasks in real-time through the implementation of dedicated computational blocks. The latter, in recent architectures, are therefore used for the execution of specific tasks that require high computational speed and system flexibility. This paper reports some case studies recently applied in the LiDAR field, with the aim of illustrating the role of FPGA technology and its benefits.

2.
Transplant Proc ; 52(10): 3112-3117, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32680595

RESUMEN

Tacrolimus is a cornerstone in the immunosuppressive therapy of kidney transplantation. The once-daily formulation of tacrolimus has been shown to improve adherence of patients without affecting short-term efficacy. However, long-term proof of once-daily tacrolimus efficacy and safety is still lacking. From January 2009 to November 2013, 170 clinically stable kidney transplant patients were offered to change from the ongoing twice-daily tacrolimus (TDT) formulation to a once-daily tacrolimus (ODT) regimen. Kidney transplant recipients agreeing to the change to be treated with an ODT regimen (n = 105, estimated glomerular filtration rate [eGFR] 57.1 ± 1.6 mL/min/1.73 m2) and patients continuing on a TDT formulation (n = 65, eGFR 52.0 ± 2.2 mL/min/1.73 m2) were prospectively followed (median follow-up time 10.4 and 12.6 years in the ODT and TDT groups, respectively, P = not significant). At the end of the follow-up, patients in both groups experienced similar eGFR (50.4 ± 2.2 vs 48.0 ± 2.7 mL/min/1.73 m2 in the ODT and TDT groups, respectively, P = not significant). No differences were observed in biopsy-proven acute rejection, overall graft survival, doubling of serum creatinine, and new onset of proteinuria. The 2 groups also had a comparable rate of death, sepsis, and neoplasia. In conclusion, ODT appears safe and effective in stable kidney graft recipients even 10 years after transplantation. These findings support the use of ODT as a primary tacrolimus formulation in patients with kidney transplantation.


Asunto(s)
Rechazo de Injerto/prevención & control , Terapia de Inmunosupresión/métodos , Inmunosupresores/administración & dosificación , Trasplante de Riñón , Tacrolimus/administración & dosificación , Estudios de Cohortes , Esquema de Medicación , Femenino , Supervivencia de Injerto/efectos de los fármacos , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos
3.
Transplant Proc ; 51(1): 120-123, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30655157

RESUMEN

BACKGROUND: Living donor kidney transplantation (LDKT) is the best therapy for patients with chronic renal failure. Its advantages, compared with cadaveric transplantation, include the possibility of avoiding dialysis, the likelihood of best outcome, and donor pool expansion. Careful assessment of potential donors is important to minimize the risks and ensure success. However, the proportion of donors disqualified has been poorly investigated. The aim of this work is to describe our experience and present the main reasons for missed donation. METHODS: This was a single-center, retrospective study of all potential donors and recipients evaluated for LDKT between January 2008 and December 2017. RESULTS: During the period of study, 81 donor-recipient pairs were evaluated. Of these, 45.7% were disqualified and 37 LDKTs were carried out. LDKT was the first choice in 68% of cases and preemptive in 20%; 60% of transplants were among family members. Sex distribution revealed a prevalence of females in the donor group (69%) and males in the recipient group (70%). The mean living donor age was 53 ± 9.5 years; the mean recipient age was lower in recipients listed in the living transplant program than those listed for cadaver transplantation (45.8 ± 13.4 vs 54.2 ± 11.08; P < .0001). Reasons for denial included hypertension (18.9%), deceased donor transplant performed during the study period (16.2%), urologic pathology (13.5%), incompatibility (13.5%), withdrawal of consent by donor or recipient (13.5%), psychological unsuitability (8.1%), donor cancer (5.4%), and reduced renal clearance (2.7%). CONCLUSION: LDKT is considered an option especially for younger recipients. Of the potential kidney living donors, 45.7% were disqualified during the evaluation, with medical reasons being the primary cause.


Asunto(s)
Fallo Renal Crónico/cirugía , Trasplante de Riñón/métodos , Donadores Vivos/provisión & distribución , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos
4.
Transplant Proc ; 49(6): 1270-1275, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28735992

RESUMEN

BACKGROUND: Information on physical performance in renal transplantation is limited because of the shortage of specifically designed evaluation instruments. Therefore, we elaborated and validated the Global Performance Status (GloPerSta) score to provide a new and comprehensive tool, exploring the different components of physical performance in kidney transplant patients. METHODS: We elaborated the GloPerSta score on the basis of the data obtained from a cross-sectional study, in which we evaluated the physical performance of a cohort of kidney transplant patients. The results of these analyses were weighted to describe the different contribution of any single test, via the generation of a structural equation model, resulting in the definition of the GloPerSta. Then, to internally validate this score, we studied its correlation with clinical parameters and quality of life (evaluated as KDQOL-SF, Kidney Disease Quality of Life-Short Form) in the same patient population. RESULTS: We enrolled 132 patients in whom the functional tests revealed a great heterogeneity. GloPerSta allowed the stratification of the patients in 3 different physical performance categories (low: score 0-11; medium: 12-22; high: 23-33). Internal validation showed that GloPerSta was directly and significantly correlated with the quality of life and allograft function, independent of the time from transplantation. CONCLUSIONS: The GloPerSta is a reliable tool to assess physical performance in a kidney transplant population. Its application might be of help in identifying patients needing intensive and personalized rehabilitation programs.


Asunto(s)
Evaluación de la Discapacidad , Indicadores de Salud , Trasplante de Riñón/rehabilitación , Modelos Teóricos , Adulto , Estudios de Cohortes , Estudios Transversales , Femenino , Humanos , Enfermedades Renales/fisiopatología , Enfermedades Renales/cirugía , Masculino , Persona de Mediana Edad , Periodo Posoperatorio , Calidad de Vida , Reproducibilidad de los Resultados , Encuestas y Cuestionarios , Resultado del Tratamiento
5.
J Biol Regul Homeost Agents ; 31(2 Suppl 1): 11-22, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28691449

RESUMEN

This preliminary study aims to establish the Virtual Chromoendoscopic Magnification (VCM) feasibility to visualize and distinguish the Intraepithelial Papillary Capillary Loops (IPCL) patterns of benign oral pathologies from malignant ones. Thirty-one consecutive subjects affected by oral lesions/pathologies underwent white light examination and VCM imaging by the Narrow Band Imaging System (Olympus Medical Systems Corp., Tokyo, Japan). A class system of four IPCL types corresponding to progressive vessel disarray was adopted. IPCL type IV were considered criterion of “malignancy”. A histopathological exam completed the diagnosis: sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated. IPCL patterns of benign oral entities ranged from types I to III. IPCL type IV was associated with malignancy in 4 out of 6 cases. Sensitivity, specificity, PPV, and NPV were 100%, 93%, 67% and 100%, respectively. This study preliminarily describes IPCL patterns of different oral mucosal diseases and confirms the association between IPCL IV and oral cancer.


Asunto(s)
Neoplasias de la Boca/diagnóstico por imagen , Neoplasias de la Boca/patología , Boca/diagnóstico por imagen , Imagen de Banda Estrecha , Humanos , Sensibilidad y Especificidad
6.
Transplant Proc ; 49(4): 650-657, 2017 May.
Artículo en Inglés | MEDLINE | ID: mdl-28457365

RESUMEN

BACKGROUND: Kidney transplantation (KT) immunosuppression may induce bone tissue damage with bone mineral density (BMD) loss increasing bone fractures risk. Steroid therapy is considered the major player, but others factors are still under review. PATIENTS AND METHODS: We designed an observational retrospective cohort study to evaluate bone damage after KT. The prevalence of osteopenia, osteoporosis, bone fractures, and the associated risk factors were investigated. The following parameters were recorded before transplantation and at the last follow-up: demographic indexes, cumulative steroid dose (CSD), dialytic and transplantologic age, previous nephropathy, femoral and lumbar BMD, fractures, immunosuppressors, calcemia, phosphoremia, rejection episodes, estimated glomerular filtration rate, and parathyroid hormone and vitamin D levels. Stata software (Stata Corporation, College Station, Texas, United States) was used for the statistical analysis, to perform the Fisher's exact test, Kruskal-Wallis test, Student t test, as well as univariate and multivariate analyses. RESULTS: The analyzed cohort was composed of 297 patients (65.3% males and 34.7% females). Sixty percent of KT patients had normal BMD, 24% had osteopenia, and 15% had osteoporosis. Twelve percent were victims of bone fractures (8.4% minor, 2% femoral, and 1.7% vertebral). A significant correlation (P <.05) was observed for both osteopenia and osteoporosis with menopause, transplantologic age, CSD, previous glomerulonephritis, and mammalian target of rapamycin (mTOR) inhibitors treatment (imTOR). CONCLUSION: This study confirms the correlation between CSD (both before and after transplantation) and post-transplantation bone damage. It also shows that a large fraction of these patients had normal BMD related with a low steroid dose in our protocols. This correlation between imTOR assumption and osteoporosis deserves attention and warrants further in vitro analyses to be performed.


Asunto(s)
Corticoesteroides/efectos adversos , Enfermedades Óseas/epidemiología , Enfermedades Óseas/etiología , Huésped Inmunocomprometido , Inmunosupresores/efectos adversos , Trasplante de Riñón , Adulto , Anciano , Densidad Ósea/efectos de los fármacos , Estudios de Cohortes , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Retrospectivos , Factores de Riesgo , Texas
7.
Eur Rev Med Pharmacol Sci ; 20(11): 2413-7, 2016 06.
Artículo en Inglés | MEDLINE | ID: mdl-27338069

RESUMEN

OBJECTIVE: Levodopa is the gold standard in the pharmacological treatment of Parkinson's disease (PD) and its oral administration is associated with the development of disabling motor and non-motor complications in advanced disease. Levodopa is rapidly metabolized and has a short plasma half-life thus requiring frequent, repeated dosing. Impaired gastric emptying is common in PD, and likely contributes to the unpredictable motor responses observed with orally-dosed levodopa. A new therapeutic protocol for patients with advanced PD include a carbidopa/levodopa combination using continuous, modulated enteral administration achieved inserting a Jejunal Extension Tube Placement through Percutaneous Endoscopic Gastrostomy (PEG-J). The aim of this work is to assess efficacy and safety of levodopa-carbidopa intestinal gel (LCIG) delivered continuously through an intrajejunal percutaneous tube (PEG-J). PATIENTS AND METHODS: We enrolled 11 adults with advanced PD and preserved sensitivity to L-dopa. For pre-procedural endoscopic evaluation each patient underwent a diagnostic esophagogastroduodenoscopy (EGD) 7 days before PEG-J placement to evaluate the presence of gastric anatomical or wall anomalies and the presence of oesophageal or gastric varices. Treatment with LCIG, consisting of a water-based suspension containing micronized levodopa (20 mg/mL) and carbidopa (5 mg/mL) in methylcellulose (Duodopa®), was administered by continuous jejunal infusion for 12h/day using a portable pump (CADD-Legacy) by PEG-J. Clinical evaluations were performed at baseline (T0) before LCIG initiation, and after 3 (T3) and 6 (T6) months of therapy. The efficacy and safety outcomes were assessed by using the Unified Parkinson's Disease Rating Scale (UPDRS) parts II, III and IV. RESULTS: Mean age of patients was 71.18 ± 5.4 SD at LCIG initiation. Out of the 11 patients, 2 (18%) dropped-out LCIG at T3. Patients showed statistically significant (p < 0.05) higher performances in activities of daily living and a statistically significant (p < 0.001) lower incidence and severity of motor fluctuations, as rating by UPDRS part IV, compared to their best oral therapy. During observational period, 5 patients experienced adverse events. Success rate for PEG-J placement was 100%. CONCLUSIONS: Our work shows that continuous intrajejunal infusion of LCIG ensures a reduction in motor Fluctuations compared to oral administration of levodopa-carbidopa in advanced PD. Based on our results and on the evidence emerging in the literature, this therapeutic approach should be the gold standard for therapy in these patients.


Asunto(s)
Antiparkinsonianos/administración & dosificación , Carbidopa/administración & dosificación , Endoscopía Gastrointestinal/métodos , Levodopa/administración & dosificación , Enfermedad de Parkinson/tratamiento farmacológico , Actividades Cotidianas , Combinación de Medicamentos , Gastrostomía , Humanos
8.
Eur Rev Med Pharmacol Sci ; 19(21): 4119-22, 2015 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-26592837

RESUMEN

Gastric antral vascular ectasia (GAVE) is an uncommon disorder observed in patients with liver cirrhosis, causing upper gastro-intestinal haemorrhage. GAVE is diagnosed through esophagogastroduodenoscopy and is characterized by the presence of visible columns of red tortuous enlarged vessels along the longitudinal folds of the antrum (i.e., so-called watermelon stomach). Pharmacological, endoscopic and surgical approaches have been proposed for the treatment of GAVE. Endoscopy represents the gold standard for GAVE treatment. The most widely used endoscopic approach is represented by Neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Argon plasma coagulation (APC) has been proven to be more efficient in terms of costs and complication rates than and equally effective as Nd:YAG. Other endoscopic procedures proposed for this treatment are banding ligature (EBL) and sclerotherapy with Polidocanol. Refractory GAVE represents a therapeutic challenge because it may cause persistent anemia, often leading to repeated blood transfusions due to the inefficacy of pharmacological and endoscopic therapeutic approaches. Endoscopic band ligation (EBL) has been shown to be superior to APC in the treatment of refractory GAVE. Surgical antrectomy by Billroth I anastomosis can be considered in selected cases. In this study, we report a successful endoscopic treatment of refractory GAVE by using a combination of submucosal injection of 1% Polidocanol at the four antral quadrants and subsequent application of APC on the visible antral lesions in two patients.


Asunto(s)
Coagulación con Plasma de Argón/métodos , Endoscopía Gastrointestinal/métodos , Ectasia Vascular Antral Gástrica/diagnóstico , Ectasia Vascular Antral Gástrica/terapia , Polietilenglicoles/administración & dosificación , Escleroterapia/métodos , Anciano , Femenino , Ectasia Vascular Antral Gástrica/complicaciones , Hemorragia Gastrointestinal/diagnóstico , Hemorragia Gastrointestinal/etiología , Hemorragia Gastrointestinal/terapia , Humanos , Cirrosis Hepática/complicaciones , Cirrosis Hepática/diagnóstico , Cirrosis Hepática/terapia , Masculino , Polidocanol , Resultado del Tratamiento
10.
Ciudad Autónoma de Buenos Aires; Ministerio de Salud de la Nación. Dirección de Investigación en Salud; 2014. 1 p.
No convencional en Español | ARGMSAL, BINACIS | ID: biblio-1511096

RESUMEN

INTRODUCCIÓN La Escala de Evaluación de las Discapacidades de la OMS (WHO-DAS-2.0, World Health Organization Disability Assessment Schedule 2.0) evalúa el grado de discapacidad de una persona a partir de los cambios en el funcionamiento, sus niveles de dificultad y/o limitación para el desempeño de actividades (vitales y de la vida diaria) y restricciones a la participación por barreras ambientales y actitudinales. OBJETIVOS Analizar las propiedades psicométricas de la versión en español del WHO-DAS 2.0 para evaluar la discapacidad en mayores de 18 años que sufrieron traumatismo encefálico (TEC) por siniestros de tránsito en Mar del Plata. MÉTODOS Se entrevistó a 45 personas después de seis meses de ocurrida la lesión. Se analizo a) la consistencia interna mediante Alfa de Cronbach de la comprensión y comunicación, la movilidad, el autocuidado, la capacidad de relacionarse con otras personas, las actividades de la vida y la participación en la sociedad; b) la validez de criterio a partir de la correlación parcial y global con la Escala de Glasgow Ampliada (GOSE) y la Escala de Independencia Funcional (FIM). Se realizó un Análisis en Componentes Principales (ACP) y una Clasificación Jerárquica y Partición; se compararon puntuaciones parciales y totales en dos grupos de distinta severidad mediante la prueba H de Kruskal Wallis. Finalmente, se analizó la distribución espacial georreferenciada de los domicilios. RESULTADOS Se obtuvieron valores de Alfa de Cronbach mayores a 0,8, coeficientes de Pearson y Spearman mayores a 0,85 con la GOSE y correlación de Spearman igual a 0,90 con la FIM. El ACP mostró tres clases de distinta severidad y dos grupos de dimensiones correspondientes a las áreas física y social. La FIM mostró alta correlación inversa con la primera. Se observó alta capacidad discriminante entre subgrupos de distinta severidad. La inclusión de personas desocupadas por razones de salud en el ítem trabajo fuera del hogar (TFH) mostró mayor correlación que las obtenidas sin incluirlas. El tiempo de educación tiene alta correlación con la GOSE y media con WHO-DAS 2.0. El análisis espacial mostró que los domicilios se ubican en la periferia de Mar del Plata. Discusión El WHO-DAS 2.0 permite evaluar la discapacidad por TEC en el tránsito. La inclusión de los desocupados por razones de salud en el dominio TFH es importante.


Asunto(s)
Accidentes de Tránsito , Clasificación Internacional del Funcionamiento, de la Discapacidad y de la Salud , Lesiones Traumáticas del Encéfalo
13.
Transpl Infect Dis ; 14(1): 72-4, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21466642

RESUMEN

Erythema nodosum (EN) is a cutaneous inflammatory reaction, usually reported in young women, but it is rarely observed among transplant patients. Localization in the lower extremities is typical, mostly involving the anterior surfaces of the legs. Several viral, bacterial, mycotic, and non-infectious etiologies, such as autommune disorders, drugs, inflammatory bowel diseases, sarcoidosis, pregnancy, and malignancies, have been found. We describe the case of a young woman kidney transplant recipient developing bilateral, erythematous, warm nodules localized on the anterior surface of her legs after antibiotic treatment for pneumonia with levofloxacin. Her immunosuppression was sirolimus and mycophenolate mofetil. EN was diagnosed by skin biopsy; microscopic examination showed septal panniculitis with granulomas. As a complete remission of the lesions was obtained in our patient after interruption of levofloxacin therapy, we suspect that levofloxacin was involved in the pathogenesis of EN. In fact, the management of EN is based on the treatment of underlying or associated conditions.


Asunto(s)
Antibacterianos/efectos adversos , Eritema Nudoso/etiología , Trasplante de Riñón/efectos adversos , Levofloxacino , Ofloxacino/efectos adversos , Neumonía Bacteriana/tratamiento farmacológico , Adulto , Antibacterianos/uso terapéutico , Eritema Nudoso/diagnóstico , Eritema Nudoso/patología , Femenino , Humanos , Pierna/patología , Ofloxacino/uso terapéutico , Neumonía Bacteriana/microbiología , Piel/patología
14.
Nature ; 476(7361): 421-4, 2011 Aug 24.
Artículo en Inglés | MEDLINE | ID: mdl-21866154

RESUMEN

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

15.
Minerva Gastroenterol Dietol ; 56(4): 389-95, 2010 Dec.
Artículo en Italiano | MEDLINE | ID: mdl-21139538

RESUMEN

AIM: The purpose of this study was to evaluate the efficacy of policosanols in the treatment of associated hyperlipidemia in patients with non-alcoholic fatty liver disease (NAFLD). METHODS: We conducted a retrospective study on 52 patients with NAFLD. Pretreatment patients' data (total cholesterol, LDL cholesterol, triglycerides, ALT, and AST) were collected and analyzed. Furthermore, based on weight and height, we calculated the Body Mass Index (BMI) and, based on blood glucose and insulin levels, we estimated the Human Omeostatic Assesment Index (HOMA). After that, all patients were treated with a policosanols' supplement (Frilipid®) and a hypocaloric balanced diet, and then followed over time with quarterly inspections. We collected and analyzed data on three subsequent quarterly monitoring during treatment. RESULTS: The collected and analyzed data showed a significant reduction in total cholesterol, LDL cholesterol and HOMA index (P<0.002). It was also found a trend not statistically significant for a marked reduction in ALT, AST, triglycerides, and BMI. CONCLUSION: The use of policosanols is shown effective in the treatment of associated hyperlipidemia and insulin resistance in patients with fatty liver disease.


Asunto(s)
Anticolesterolemiantes/uso terapéutico , Alcoholes Grasos/uso terapéutico , Hidroximetilglutaril-CoA Reductasas/genética , Hiperlipidemias/tratamiento farmacológico , Anciano , Biomarcadores/sangre , Índice de Masa Corporal , Colesterol/sangre , LDL-Colesterol/sangre , Hígado Graso/sangre , Hígado Graso/diagnóstico , Hígado Graso/tratamiento farmacológico , Hígado Graso/etiología , Femenino , Estudios de Seguimiento , Humanos , Hiperlipidemias/sangre , Hiperlipidemias/complicaciones , Hiperlipidemias/diagnóstico , Hiperlipidemias/etiología , Masculino , Persona de Mediana Edad , Enfermedad del Hígado Graso no Alcohólico , Obesidad/complicaciones , Estudios Retrospectivos , Transcripción Genética/efectos de los fármacos , Resultado del Tratamiento , Triglicéridos/sangre
17.
Science ; 330(6006): 944-6, 2010 Nov 12.
Artículo en Inglés | MEDLINE | ID: mdl-20947727

RESUMEN

Soft gamma repeaters (SGRs) and anomalous x-ray pulsars form a rapidly increasing group of x-ray sources exhibiting sporadic emission of short bursts. They are believed to be magnetars, that is, neutron stars powered by extreme magnetic fields, B ~ 10(14) to 10(15) gauss. We report on a soft gamma repeater with low magnetic field, SGR 0418+5729, recently detected after it emitted bursts similar to those of magnetars. X-ray observations show that its dipolar magnetic field cannot be greater than 7.5 × 10(12) gauss, well in the range of ordinary radio pulsars, implying that a high surface dipolar magnetic field is not necessarily required for magnetar-like activity. The magnetar population may thus include objects with a wider range of B-field strengths, ages, and evolutionary stages than observed so far.

19.
Science ; 327(5966): 663-5, 2010 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-20044540

RESUMEN

Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources.

20.
Science ; 325(5945): 1222-3, 2009 Sep 04.
Artículo en Inglés | MEDLINE | ID: mdl-19729650

RESUMEN

White dwarfs typically have masses in a narrow range centered at about 0.6 solar mass (M(o)). Only a few ultramassive white dwarfs (mass > 1.2 M(o)) are known. Those in binary systems are of particular interest, because a small amount of accreted mass could drive them above the Chandrasekhar limit, beyond which they become gravitationally unstable. Using data from the x-ray multimirror mission (XMM)-Newton satellite, we show that the x-ray pulsator RX J0648.0-4418 is a white dwarf with mass > 1.2 M(o), based on dynamical measurements only. This ultramassive white dwarf in a post-common envelope binary with a hot subdwarf can reach the Chandrasekhar limit, and possibly explode as a type Ia supernova, when its helium-rich companion will transfer mass at an increased rate through Roche lobe overflow.

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