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1.
Epidemiol Psychiatr Sci ; 32: e1, 2023 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-36624694

RESUMEN

AIMS: Childhood adversities (CAs) predict heightened risks of posttraumatic stress disorder (PTSD) and major depressive episode (MDE) among people exposed to adult traumatic events. Identifying which CAs put individuals at greatest risk for these adverse posttraumatic neuropsychiatric sequelae (APNS) is important for targeting prevention interventions. METHODS: Data came from n = 999 patients ages 18-75 presenting to 29 U.S. emergency departments after a motor vehicle collision (MVC) and followed for 3 months, the amount of time traditionally used to define chronic PTSD, in the Advancing Understanding of Recovery After Trauma (AURORA) study. Six CA types were self-reported at baseline: physical abuse, sexual abuse, emotional abuse, physical neglect, emotional neglect and bullying. Both dichotomous measures of ever experiencing each CA type and numeric measures of exposure frequency were included in the analysis. Risk ratios (RRs) of these CA measures as well as complex interactions among these measures were examined as predictors of APNS 3 months post-MVC. APNS was defined as meeting self-reported criteria for either PTSD based on the PTSD Checklist for DSM-5 and/or MDE based on the PROMIS Depression Short-Form 8b. We controlled for pre-MVC lifetime histories of PTSD and MDE. We also examined mediating effects through peritraumatic symptoms assessed in the emergency department and PTSD and MDE assessed in 2-week and 8-week follow-up surveys. Analyses were carried out with robust Poisson regression models. RESULTS: Most participants (90.9%) reported at least rarely having experienced some CA. Ever experiencing each CA other than emotional neglect was univariably associated with 3-month APNS (RRs = 1.31-1.60). Each CA frequency was also univariably associated with 3-month APNS (RRs = 1.65-2.45). In multivariable models, joint associations of CAs with 3-month APNS were additive, with frequency of emotional abuse (RR = 2.03; 95% CI = 1.43-2.87) and bullying (RR = 1.44; 95% CI = 0.99-2.10) being the strongest predictors. Control variable analyses found that these associations were largely explained by pre-MVC histories of PTSD and MDE. CONCLUSIONS: Although individuals who experience frequent emotional abuse and bullying in childhood have a heightened risk of experiencing APNS after an adult MVC, these associations are largely mediated by prior histories of PTSD and MDE.


Asunto(s)
Trastorno Depresivo Mayor , Trastornos por Estrés Postraumático , Adulto , Humanos , Adolescente , Adulto Joven , Persona de Mediana Edad , Anciano , Trastornos por Estrés Postraumático/epidemiología , Trastornos por Estrés Postraumático/etiología , Trastornos por Estrés Postraumático/diagnóstico , Trastorno Depresivo Mayor/psicología , Depresión/psicología , Encuestas y Cuestionarios , Vehículos a Motor
2.
Psychol Med ; 53(6): 2553-2562, 2023 04.
Artículo en Inglés | MEDLINE | ID: mdl-35094717

RESUMEN

BACKGROUND: Racial and ethnic groups in the USA differ in the prevalence of posttraumatic stress disorder (PTSD). Recent research however has not observed consistent racial/ethnic differences in posttraumatic stress in the early aftermath of trauma, suggesting that such differences in chronic PTSD rates may be related to differences in recovery over time. METHODS: As part of the multisite, longitudinal AURORA study, we investigated racial/ethnic differences in PTSD and related outcomes within 3 months after trauma. Participants (n = 930) were recruited from emergency departments across the USA and provided periodic (2 weeks, 8 weeks, and 3 months after trauma) self-report assessments of PTSD, depression, dissociation, anxiety, and resilience. Linear models were completed to investigate racial/ethnic differences in posttraumatic dysfunction with subsequent follow-up models assessing potential effects of prior life stressors. RESULTS: Racial/ethnic groups did not differ in symptoms over time; however, Black participants showed reduced posttraumatic depression and anxiety symptoms overall compared to Hispanic participants and White participants. Racial/ethnic differences were not attenuated after accounting for differences in sociodemographic factors. However, racial/ethnic differences in depression and anxiety were no longer significant after accounting for greater prior trauma exposure and childhood emotional abuse in White participants. CONCLUSIONS: The present findings suggest prior differences in previous trauma exposure partially mediate the observed racial/ethnic differences in posttraumatic depression and anxiety symptoms following a recent trauma. Our findings further demonstrate that racial/ethnic groups show similar rates of symptom recovery over time. Future work utilizing longer time-scale data is needed to elucidate potential racial/ethnic differences in long-term symptom trajectories.


Asunto(s)
Depresión , Trastornos por Estrés Postraumático , Humanos , Niño , Depresión/psicología , Trastornos de Ansiedad , Ansiedad/epidemiología , Trastornos por Estrés Postraumático/epidemiología , Trastornos por Estrés Postraumático/diagnóstico , Etnicidad/psicología
3.
Clin Radiol ; 70(5): 502-6, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25649441

RESUMEN

AIM: To identify factors affecting upgrade rates from B5a (non-invasive) preoperative core biopsies to invasive disease at surgery and ways to improve screening performance. MATERIAL AND METHODS: This was a retrospective analysis of 1252 cases of B5a biopsies across all six Scottish Breast Screening Programmes (BSPs), ranging between 2004 and 2012. Final surgical histopathology was correlated with radiological and biopsy factors. Data were analysed using basic Microsoft Excel and standard Chi-squared test used for evaluating statistical significance. RESULTS: B5a upgrade rates for the units ranged from 19.2% to 29.2%, with an average of 23.6%. Mean sizes of invasive tumours were small (3-11 mm). The upgrade rate was significantly higher for cases where the main mammographic abnormality was mass, distortion, or asymmetry, compared with micro-calcification alone (33.2% versus 21.7%, p = 0.0004). The upgrade rate was significantly lower with the use of large-volume vacuum-assisted biopsy (VAB) devices than 14 G core needles (19.9% versus 26%, p = 0.013); in stereotactic than ultrasound-guided biopsies (21.2% versus 36.1%, p < 0.001). Heterogeneity of data from different centres limited evaluation of other potential factors. CONCLUSION: Upgrade rates are lower for cases with micro-calcification as the sole mammographic feature with the use of VAB devices. Nevertheless, there is variation in practice across Scottish BSPs, including first-line biopsy technique and/or device; and it is of interest that a few centres maintain low upgrade rates despite not using VAB routinely for biopsy of micro-calcification.


Asunto(s)
Biopsia/métodos , Neoplasias de la Mama/patología , Calcinosis/patología , Carcinoma in Situ/patología , Carcinoma Ductal de Mama/patología , Neoplasias de la Mama/cirugía , Carcinoma Ductal de Mama/cirugía , Femenino , Humanos , Mamografía , Clasificación del Tumor , Invasividad Neoplásica , Estudios Retrospectivos , Escocia , Vacio
4.
Eur J Pain ; 17(8): 1243-51, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23335385

RESUMEN

BACKGROUND: Musculoskeletal pain is common after motor vehicle collision (MVC). The study objective was to evaluate distribution of pain and predictors of widespread musculoskeletal pain in the early aftermath (within 48 h) of collision. METHODS: European American adults aged 18-65 years presenting to the emergency department (ED) after collision who were discharged to home after evaluation were eligible. Evaluation included an assessment of reported pre-collision psychological characteristics, crash characteristics, current pain severity and location, and current psychological symptoms. Adjusted risk ratios were estimated using generalized linear models. RESULTS: Among 890 participants included in the study, 589/890 (66%) had pain in three or more regions, and 192/890 (22%) had widespread musculoskeletal pain (pain in seven or more regions). In adjusted analyses, the presence of widespread pain was strongly associated with depressive and somatic symptoms prior to collision, pain catastrophizing, and acute psychological symptoms, and was not associated with most collision characteristics (road speed limit, extent of vehicle damage, collision type, driver vs. passenger, airbag deployment). The reported number of body regions that struck an object during the collision was associated with both reported pre-collision depressive symptoms and with widespread pain. CONCLUSION: More than one in five individuals presenting to the ED in the hours after MVC have widespread pain. Widespread pain is strongly associated with patient characteristics known to be modulated by supraspinal mechanisms, suggesting that stress-induced hyperalgesia may influence acute widespread pain after collision.


Asunto(s)
Accidentes de Tránsito/psicología , Dolor Musculoesquelético/psicología , Dolor/psicología , Adolescente , Adulto , Anciano , Servicio de Urgencia en Hospital/estadística & datos numéricos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Vehículos a Motor , Dolor Musculoesquelético/fisiopatología , Adulto Joven
5.
Br J Surg ; 97(8): 1198-206, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20602497

RESUMEN

BACKGROUND: Routine laxatives may expedite gastrointestinal recovery and early tolerance of food within an enhanced recovery after surgery (ERAS) programme. Combined with carbohydrate loading and oral nutritional supplements (ONS), it may further enhance recovery of gastrointestinal function and promote earlier overall recovery. METHODS: Seventy-four patients undergoing liver resection were randomized in a two-by-two factorial design to receive either postoperative magnesium hydroxide as a laxative, preoperative carbohydrate loading and postoperative ONS, their combination or a control group. Patients were managed within an ERAS programme of care. The primary outcome measure was time to first passage of stool. Secondary outcome measures were gastric emptying, postoperative oral calorie intake, time to functional recovery and length of hospital stay. RESULTS: Sixty-eight patients completed the trial. The laxative group had a significantly reduced time to passage of stool: median (interquartile range) 4 (3-5) versus 5 (4-6) days (P = 0.034). The ONS group showed a trend towards a shorter time to passage of stool (P = 0.076) but there was no evidence of interaction in patients randomized to the combination regimen. Median length of hospital stay was 6 (4-7) days. There were no differences in secondary outcomes between groups. CONCLUSION: Within an ERAS protocol for patients undergoing liver resection, routine postoperative laxatives result in an earlier first passage of stool but the overall rate of recovery is unaltered.


Asunto(s)
Suplementos Dietéticos , Laxativos/administración & dosificación , Hepatopatías/cirugía , Hígado/cirugía , Hidróxido de Magnesio/administración & dosificación , Administración Oral , Anciano , Ingestión de Energía , Femenino , Vaciamiento Gástrico , Humanos , Tiempo de Internación , Hepatopatías/fisiopatología , Masculino , Persona de Mediana Edad , Cuidados Posoperatorios , Estudios Prospectivos , Recuperación de la Función
7.
Br J Surg ; 96(2): 197-205, 2009 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-19160347

RESUMEN

BACKGROUND: Postoperative outcomes were studied in relation to adverse nutritional risk (body mass index (BMI) below 20 kg/m(2)), advanced age (80 years or more) and co-morbidity (American Society of Anesthesiologists (ASA) grade III-IV) in patients undergoing colorectal resection within an enhanced recovery after surgery programme. METHODS: Outcomes were audited prospectively in 1035 patients. Morbidity and mortality were compared with those predicted using the Portsmouth Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity, and a multivariable model was used to determine independent predictors of outcome. RESULTS: Postoperative morbidity was lower than predicted (observed to expected 0.68; P < 0.001). Independent predictors of delayed mobilization were ASA III-IV (P < 0.001) and advanced age (P = 0.025). Prolonged hospital stay was related to advanced age (P = 0.002), ASA III-IV (P < 0.001), male sex (P = 0.037) and rectal surgery (P < 0.001). Morbidity was related to ASA III-IV (P = 0.004), male sex (P = 0.023) and rectal surgery (P = 0.002). None of the factors predicted 30-day mortality. CONCLUSION: Age and nutritional status were not independent determinants of morbidity or mortality. Pre-existing co-morbidity was an independent predictor of several outcomes.


Asunto(s)
Colon/cirugía , Neoplasias Colorrectales/cirugía , Complicaciones Posoperatorias/etiología , Recto/cirugía , Factores de Edad , Anciano , Anciano de 80 o más Años , Anastomosis Quirúrgica/rehabilitación , Neoplasias Colorrectales/rehabilitación , Ambulación Precoz , Estudios de Factibilidad , Femenino , Humanos , Tiempo de Internación , Masculino , Persona de Mediana Edad , Cooperación del Paciente , Cuidados Posoperatorios , Recuperación de la Función , Reoperación , Índice de Severidad de la Enfermedad , Resultado del Tratamiento
8.
Heart ; 95(4): 318-26, 2009 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-18653574

RESUMEN

OBJECTIVE: To compare the long-term outcomes in women and men after valve replacement surgery. DESIGN: Observational study. SETTING: Postoperative aortic valve replacement (AVR) or mitral valve replacement (MVR). PATIENTS: 3118 patients (1261 women, 1857 men) who underwent AVR or MVR between 1976 and 2006 (2255 AVR, 863 MVR), with mean follow-up of 5.6 (4.5) years. MAIN OUTCOME MEASURES: The independent effect of gender on the risk of long-term complications (reoperation, stroke and death) after valve replacement surgery using multivariate actuarial methods. RESULTS: After implantation of an aortic valve bioprosthesis, women had a significantly lower rate of reoperation compared to men (comorbidity-adjusted hazard ratio (HR) 0.4; 95% confidence intervals (CI) 0.2 to 0.9). In contrast, if an aortic mechanical prosthesis had been implanted, women were more at risk for late stroke compared to men (HR 1.7; CI 1.1 to 2.7). After adjustment for age and co-morbidities, women had significantly better long-term survival compared to men after bioprosthetic AVR (HR 0.5; CI 0.3 to 0.6), but there was no survival difference between genders after mechanical AVR. Trends existed towards better survival for women after bioprosthetic MVR (HR 0.6; CI 0.4 to 1.0) and mechanical MVR (HR 0.8; CI 0.5 to 1.1). CONCLUSION: The long-term outcomes after valve replacement surgery differ between women and men. Although women have more late strokes after valve replacement, they undergo fewer reoperations and have better overall long-term survival compared to men.


Asunto(s)
Válvula Aórtica/cirugía , Enfermedades de las Válvulas Cardíacas/cirugía , Implantación de Prótesis de Válvulas Cardíacas , Válvula Mitral/cirugía , Anciano , Anciano de 80 o más Años , Bioprótesis , Femenino , Humanos , Masculino , Persona de Mediana Edad , Modelos de Riesgos Proporcionales , Estudios Prospectivos , Falla de Prótesis , Reoperación , Factores Sexuales , Tasa de Supervivencia , Resultado del Tratamiento
9.
Surgeon ; 6(6): 361-5, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19110825

RESUMEN

INTRODUCTION: There is a traditional belief that that an inguinal hernia can be the result of increased intra-abdominal pressure (IAP) and therefore the development of a hernia may be attributed to single strenuous or recurrent strenuous events. As a result of this, litigation in this area is frequent. METHODS: Medline was searched for English language publications using the keywords of 'hernia' or 'hernia AND recurrence' combined with 'work related', 'physical activity' and 'intra abdominal pressure'. The reference lists of appropriate papers identified on the original search were also checked to identify all related publications. RESULTS: The search revealed 268 papers of which 59 were identified as appropriate to the subject of this review. Although publications in this area are scarce, from the literature available to date, there is no evidence to support the idea that single or recurrent strenuous events or early return to work related activity should result in the formation or recurrence of an inguinal hernia. CONCLUSION: Although immediate pain at the time of an intensive or recurrent activity followed by a new diagnosis of a hernia supports a link between the activity and the hernia occurrence, it is likely that a congenital or acquired weakness in the connective tissue or muscles of the patient meant that hernia occurrence was almost inevitable. This may have significant implications regarding 'work related' hernia and its associated litigation.


Asunto(s)
Hernia Inguinal/epidemiología , Enfermedades Profesionales/epidemiología , Hernia Abdominal/epidemiología , Hernia Inguinal/fisiopatología , Humanos , Enfermedades Profesionales/fisiopatología , Presión , Recurrencia
10.
Br J Surg ; 95(8): 969-75, 2008 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-18618897

RESUMEN

BACKGROUND: Accelerated recovery from surgery has been achieved when patients are managed within a multimodal Enhanced Recovery After Surgery (ERAS) protocol. This study evaluated the benefit of an ERAS programme for patients undergoing liver resection. METHODS: The ERAS protocol of epidural analgesia, early oral intake and early mobilization was studied prospectively in a consecutive series of 61 patients. Outcomes were compared with those in a consecutive series of 100 patients who underwent liver resection before the start of the study. Endpoints were postoperative length of hospital stay, postoperative resumption of oral intake, readmissions, morbidity and mortality. RESULTS: Fifty-six patients (92 per cent) in the ERAS group tolerated fluids within 4 h of surgery and a normal diet on day 1 after surgery. Median hospital stay, including readmissions, was 6.0 days compared with 8.0 days in the control group (P < 0.001). There were no significant differences in rates of readmission (13 and 10.0 per cent respectively), morbidity (41 and 31.0 per cent) and mortality (0 and 2.0 per cent) between ERAS and control groups. CONCLUSION: The ERAS fast-track protocol is safe and effective for patients undergoing liver resection. It allows early oral intake, promotes faster postoperative recovery and reduces hospital stay.


Asunto(s)
Hepatectomía/rehabilitación , Tiempo de Internación/estadística & datos numéricos , Neoplasias Hepáticas/cirugía , Cuidados Posoperatorios/métodos , Adulto , Anciano , Anciano de 80 o más Años , Analgesia Epidural/estadística & datos numéricos , Estudios de Casos y Controles , Protocolos Clínicos , Ambulación Precoz/estadística & datos numéricos , Ingestión de Alimentos/fisiología , Femenino , Hepatectomía/métodos , Humanos , Masculino , Persona de Mediana Edad , Readmisión del Paciente/estadística & datos numéricos , Cuidados Posoperatorios/estadística & datos numéricos , Evaluación de Programas y Proyectos de Salud , Estudios Prospectivos , Recuperación de la Función
11.
Colorectal Dis ; 10(9): 907-10, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-18294261

RESUMEN

OBJECTIVE: Preoperative conditioning with oral fluid and carbohydrate (CHO) loading allows the patient to undergo surgery in the fed state and is associated with reduced postoperative insulin resistance. Further benefit may accrue from oral nutritional supplements (ONS) to counteract the fasting associated with mechanical bowel preparation (MBP). In this study we assess the ability to prescribe, dispense and have patients comply with a protocol combining preoperative ONS and CHO/fluid loading during MBP. METHOD: One hundred and forty-seven patients undergoing elective left colonic or rectal resection were recruited to an Enhanced Recovery after Surgery (ERAS) programme. All patients were prescribed MBP (2 sachets Picolax). On the daytime prior to surgery, eligible patients were prescribed 2 x 200 ml of ONS (Fortijuice, Nutricia) and in the evening 800 ml oral CHO/fluid loading (Preop(R), Nutricia,). Patients were prescribed a further 400 ml of oral/CHO/fluid on the morning of surgery 2 h prior to induction of anaesthesia. Protocol compliance was audited prospectively. RESULTS: One hundred and forty-seven patients received MBP. Twenty-three patients were ineligible for oral CHO/fluid loading [diabetes (n = 22), allergy to lemon flavoured drinks (n = 1)]. Fourteen patients did not receive the preoperative CHO drinks due to failure to prescribe (n = 8) or dispense (n = 6). One hundred and ten patients were dispensed the combined ONS and CHO/fluid loading regimen, compliance rates were 83% with ONS, 80% with CHO/fluid loading and 74% with both. CONCLUSION: Approximately 74% of patients undergoing MBP can comply with preoperative conditioning with ONS and CHO/fluid loading. Prescription and dispensing requires close attention to detail.


Asunto(s)
Carbohidratos de la Dieta/administración & dosificación , Suplementos Dietéticos , Procedimientos Quirúrgicos del Sistema Digestivo , Cuidados Preoperatorios , Administración Oral , Anciano , Glucemia/metabolismo , Catárticos , Protocolos Clínicos , Colon/cirugía , Femenino , Humanos , Resistencia a la Insulina/fisiología , Masculino , Persona de Mediana Edad , Cuidados Preoperatorios/métodos , Recto/cirugía , Irrigación Terapéutica
12.
Transplant Proc ; 39(10): 3334-9, 2007 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-18089382

RESUMEN

BACKGROUND: Cyclosporine (CsA) 2-hour postdose (C2) monitoring is recommended to assess CsA exposure and predict clinical outcomes among heart transplant recipients. We correlated pharmacokinetic parameters and clinical outcomes in stable long-term heart transplant recipients monitored with C0 to develop an algorithm to convert patients from C0 to C2 monitoring. METHODS: Paired CsA C0-C2 measurements and serum creatinine levels were obtained from 35 heart transplant recipients more than 2 years posttransplantation (mean 8.8+/-4.7 years). RESULTS: The mean CsA dose and C0, C2, and C0/C2 ratio were 85+/-23 mg/12 hours, 123+/-41 ng/mL, 572+/-274 ng/mL and 4.8+/-2.1, respectively. C0 correlated weakly with C2 (r=.42, P=.011). The CsA dose correlated better with C2 (r=.58; P<.001) than with C0 (r=.37; P=.026). A good correlation was noted between C2 and the C2/C0 ratio (r=.73; P<.001), but none between C0 and the C2/C0 ratio. A borderline significant inverse correlation was noted between C0 and the worst endomyocardial biopsy score (r=-.34; P=.045), whereas none was noted with C2. Serum creatinine level did not correlate with either C2 or C0. Among patients with C0 within our target of 100 to 150 ug/L, six had C2 above 300 to 600 ug/L as suggested by the literature. CONCLUSIONS: In long-term heart transplant recipients, we could not identify a single pharmacokinetic parameter that could be used to develop an algorithm to convert from C0 to C2 monitoring; however, C2 may be better than C0 for identifying patients at risk of overexposure to CsA.


Asunto(s)
Ciclosporina/farmacocinética , Trasplante de Corazón/inmunología , Adolescente , Adulto , Anciano , Biopsia , Creatinina/sangre , Estudios Transversales , Monitoreo de Drogas/métodos , Femenino , Trasplante de Corazón/patología , Humanos , Inmunosupresores/farmacocinética , Masculino , Tasa de Depuración Metabólica , Persona de Mediana Edad
13.
Colorectal Dis ; 9(8): 745-8, 2007 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-17477852

RESUMEN

OBJECTIVE: Colonoscopy is regarded as the most sensitive method of evaluating the colon. Inadequate preparation reduces sensitivity and has adverse implications for individual patients and the Heath Service. METHOD: Data concerning the adequacy of bowel preparation and colonoscopy completion rates were prospectively collected on all colonoscopies performed in a single centre between January 1996 and January 2005. In addition, the strategy of further investigation in the event of incomplete examination was assessed. RESULTS: A total of 10 571 colonoscopies were assessed and poor bowel preparation was identified in 1788 of these cases (16.9%). The completion rate was 67.5% in those with satisfactory preparation. In patients with poor preparation, 36% of colonoscopies were complete. Incomplete examination was more likely with poor preparation [OR = 3.76 (95% CI, 3.38-4.18), P = 0.0005]. Poor preparation was more likely for inpatients [OR = 3.54 (95% CI 3.14-3.96), P = 0.0005]. Even with satisfactory preparation, inpatient completion rates were significantly less [OR = 1.78 (95% CI, 3.14-3.96), P = 0.0005). A further 542 diagnostic procedures were undertaken in the poor preparation group, an additional pound101 950 (euro149 459) in expenditure. CONCLUSION: This study supports the view that inpatients fare badly. This is partly explained by higher rates of poor preparation; however, completion rates were reduced even with adequate preparation. Failed investigation and prolonged hospital stay increase cost. Colonoscopy completion rates need to be improved with particular attention to inpatients.


Asunto(s)
Colonoscopía , Sistemas de Administración de Bases de Datos , Humanos , Estudios Prospectivos
14.
Phys Rev E Stat Nonlin Soft Matter Phys ; 74(3 Pt 2): 036307, 2006 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-17025743

RESUMEN

In an earlier paper [Nichol, Phys. Rev. E, 70, 056307 (2004)] some of the present authors presented the results of an experimental study of the dynamics of a stretched grid driven into vibration at or near its resonant frequency in isotopically pure superfluid 4He over a range of pressures at a very low temperature, where the density of normal fluid is negligible. In this paper we present the results of a similar study, based on a different grid, but now including the temperature range where the normal fluid density is no longer insignificant. The new grid is very similar to the old one except for a small difference in the character of its surface roughness. In many respects the results at low temperature are similar to those for the old grid. At low amplitudes the results are somewhat history dependent, but in essence there is no damping greater than that in vacuo. At a critical amplitude corresponding to a velocity of about 50 mms(-1) there is a sudden and large increase in damping, which can be attributed to the generation of new vortex lines. Strange shifts in the resonant frequency at intermediate amplitudes observed with the old grid are no longer seen, however they must therefore have been associated with the different surface roughness, or perhaps were due simply to some artifact of the old grid, the details of which we are currently unable to determine. With the new grid we have studied both the damping at low amplitudes due to excitations of the normal fluid, and the dependence of the supercritical damping on temperature. We present evidence that in helium at low amplitudes there may be some enhancement in the effective mass of the grid in addition to that associated with potential flow of the helium. In some circumstances small satellite resonances are seen near the main fundamental grid resonance, which are attributed to coupling to some other oscillatory system within the experimental cell.

15.
Int Semin Surg Oncol ; 3: 26, 2006 Sep 11.
Artículo en Inglés | MEDLINE | ID: mdl-16965616

RESUMEN

Radiation induced angiosarcomas (RIA) can affect breast cancer patients who had radiotherapy following conservative breast surgery. They are very rare tumors and often their diagnosis is delayed due to their benign appearance and difficulty in differentiation from radiation induced skin changes. Therefore it is very important that clinicians are aware of their existence. We report here a case of RIA followed by discussion and review of literature.

16.
Phys Rev E Stat Nonlin Soft Matter Phys ; 74(5 Pt 2): 056305, 2006 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17279991

RESUMEN

Phenomena following a rapid mechanical quench of liquid 4He from its normal to its superfluid phase are reported and discussed. The mechanical expansion apparatus is an improved version of that described previously. It uses a double-cell geometry to effect a partial separation of the sample from the convolutions of the bellows that form the outer wall of the cell. Consistent with earlier work, no evidence is found for the production of quantized vortices via the Kibble-Zurek (KZ) mechanism. Although the expansion is complete within 15ms , the second-sound velocity and attenuation continue to increase for a further approximately 60ms ; correspondingly the temperature decreases. Subsequently, the temperature rises again toward its final value as the second-sound velocity and attenuation decrease. It is shown that this unexpected behavior is apparently associated with a large-amplitude second-sound oscillation produced by the expansion, and it is suggested that the observed vortices are created by the normal fluid-superfluid counterflow that constitutes the second-sound wave. If production of large-amplitude second sound is inherent to the mechanical expansion of liquid 4He through the superfluid transition, as appears to be the case for final temperatures more than 3mK from the lambda transition, the phenomenon sets a lower bound on the density of KZ vortices that can be detected in this type of experiment.

18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 70(5 Pt 2): 056307, 2004 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-15600753

RESUMEN

A systematic experimental investigation of the macroscopic flow properties of extremely pure He II in the zero temperature limit is reported, covering the pressure range 0.3

19.
Phys Rev Lett ; 92(24): 244501, 2004 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-15245085

RESUMEN

The macroscopic flow properties of pure He II are probed in the limit of zero temperature using an oscillating grid. As the oscillation amplitude passes a first critical threshold, the resonant frequency starts decreasing but the flow remains nondissipative. Beyond a second critical amplitude, the flow undergoes a transition to turbulence and becomes dissipative. Nonlinearity and hysteresis observed between the thresholds are attributed to a boundary layer of quantized vortices.

20.
Ann Saudi Med ; 22(1-2): 105-7, 2002.
Artículo en Inglés | MEDLINE | ID: mdl-17259782
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