Waveguide-saturable absorber fabricated by femtosecond pulses in YAG:Cr4+ crystal for Q-switched operation of Yb-fiber laser

A waveguide-saturable absorber with low propagation loss is fabricated by femtosecond pulses in YAG:Cr4+ crystal. Q-switch operation of a Yb fiber laser with the new saturable absorber having absorption saturation parameters similar to the bulk YAG:Cr4+ crystal is demonstrated.

Incidence and risk factors for Contegra graft infection following right ventricular outflow tract reconstruction: long-term results.

OBJECTIVES: The aim of this study was to evaluate the risk factors associated with Contegra graft (Medtronic Minneapolis, MN, USA) infection after reconstruction of the right ventricular outflow tract. METHODS: One hundred and six Contegra grafts were implanted between April 1999 and April 2010 for the Ross procedure (n = 46), isolated pulmonary valve replacement (n = 32), tetralogy of Fallot (n = 24), double-outlet right ventricle (n = 7), troncus arteriosus (n = 4), switch operation (n = 1) and redo of pulmonary valve replacement (n = 2). The median age of the patients was 13 years (range 0-54 years). A follow-up was completed in all cases with a median duration of 7.6 years (range 1.7-12.7 years). RESULTS: There were 3 cases of in-hospital mortality. The survival rate during 7 years was 95.7%. Despite the lifelong endocarditis prophylaxis, Contegra graft infection was diagnosed in 12 (11.3%) patients at a median time of 4.4 years (ranging from 0.4 to 8.7 years). Univariate analysis of preoperative, perioperative and postoperative variables was performed and the following risk factors for time to infection were identified: female gender with a hazard ratio (HR) of 0.19 (P = 0.042), systemic-to-pulmonary shunt (HR 6.46, P < 0.01), hypothermia (HR 0.79, P = 0.014), postoperative renal insufficiency (HR 11.97, P = 0.015) and implantation of permanent pacemaker during hospitalization (HR 5.29, P = 0.075). In 2 cases, conservative therapy was successful and, in 10 patients, replacement of the infected valve was performed. The Contegra graft was replaced by a homograft in 2 cases and by a new Contegra graft in 8 cases. Cox's proportional hazard model indicated that time to graft infection was significantly associated with tetralogy of Fallot (HR 0.06, P = 0.01), systemic-to-pulmonary shunt (HR 64.71, P < 0.01) and hypothermia (HR 0.77, P < 0.01). CONCLUSION: Contegra graft infection affected 11.3% of cases in our cohort, and thus may be considered as a frequent entity that can be predicted by both intraoperative and early postoperative factors. After the diagnosis of infection associated with the Contegra graft was confirmed, surgical treatment was the therapy of choice.

Survival and health in liveborn infants with transposition of great arteries--a population-based study.

OBJECTIVE: To describe treatment, survival, and morbidity for liveborn infants with isolated transposition of great arteries (TGA). DESIGN: Population-based data from 7 European registries of congenital malformations (EUROCAT). RESULTS: Ninety-seven infants were diagnosed with isolated TGA and livebirth prevalence was 2.0 per 10,000 livebirths. The majority of infants were treated with prostaglandins (83%) and 57% had a catheter atrial septostomia performed. Arterial switch surgery was performed in 78 infants, other or unknown type of surgery was performed in 3 cases, and for 6 infants there was no information on surgery. At 1 year of age 69 infants were alive (71%) and 24 (25%) were dead (4 unknown). There were 10 deaths before surgery and 58% of all deaths took place during the first week. There was no statistically significant regional difference in mortality. Eight infants diagnosed prenatally all survived to 1 year and only 71% of infants diagnosed after birth survived (P = 0.08). Data on morbidity at 1 year of age was available for 57 infants. Fifty-one infants were reported with normal health and development. CONCLUSIONS: In this population-based study survival for liveborn infants with TGA is lower than in studies published from tertiary centers. Outcome for survivors at 1 year of age seems favorable.

Levosimendan as rescue therapy after surgery for congenital heart disease

Objectives: Levosimendan, a calcium-sensitizing agent has been reported as useful for the management of patients with low cardiac output state. We report here our experience, safety and efficacy of use of levosimendan as rescue therapy after surgery for congenital heart disease. Methods: Retrospective cohort study on patients necessitating levosimendan therapy for post operative low cardiac output or severe post operative systolic and diastolic dysfunction. Twelve patients with a mean age of 2.1 years (range 7 days - 14 years old) received levosimendan. Type of surgery: 3 arterial switch, 3 correction of complete abnormal pulmonary venous return, 3 closure of VSD and correction of aortic coarctation, 3 Tetralogy of Fallot, one correction of truncus arteriosus and one palliation for single ventricle. The mean time of ECC was 203 +/- 81min. Ten patients received levosimendan for low cardiac output not responding to conventional therapy in these cases (milrinone, dopamine and noradrenaline) in the first 6 hours following entry in the ICU and 3 patients received levosimendan 3-4 days after surgery for severe systolic and diastolic dysfunction. Levosimendan was given as a drip for 24-48 hours at the dose of 0.1-0.2 mcg/ kg/min, without loading dose. Results: Significant changes were noted on mean plasmatic lactate (3.3 +/- 1.7mmole/L vs 1.8 +/-0.6mmole/L, p+0.01), mean central venous saturation (55 +/- 11% vs 68 +/- 10%, p+0.01) and mean arterio-venous difference in CO2 (9.6 +/- 4.9mmHg vs 6.7 +/- 2.1mmHg, p+0.05) for values before and at the end of levosimendan administration. There was no significant changes on heart rate, systolic pressure or central venous pressure. No adverse effect was observed. Conclusion: Levosimendan, used as rescue therapy after surgery for congenital heart disease, is safe and improves cardiac output as demonstrated with improvement of parameters commonly used clinically.

Iliac-hepatic arterial bypass for compromised collateral flow during modified Appleby operation for advanced pancreatic cancer

Involvement of the celiac trunk and common hepatic artery are two of the most common forms of vascular invasion by tumours of the distal pancreas, and until recently this finding was considered a contra-indication to resection. We described a modified Appleby operation for locally advanced distal pancreatic cancer with compromised hepatic collateral flow that needed hepatic arterial revascularization, successfully accomplished by left external iliac-hepatic arterial bypass with Dacron prosthesis. Patient recovery was uneventful and he was discharged on the 10th postoperative day. Postoperative angio-CT disclosed a patent arterial bypass. Patient is well and asymptomatic 13 months after operation. At the time of this writing, postoperative CT scan showed no evidence of disease and CA 19-9 level is normal. There is a well established rationale to perform extended resection of pancreatic carcinomas that compromise vascular structures. Modified Appleby procedure can safely be performed, has oncological advantages to palliative procedures and provides relief of pain but is reserved for selected patients. Preservation of hepatic arterial flow has utmost importance to avoid hepatobiliary complications as liver necrosis, liver abscess, gallbladder necrosis or cholecystitis. In this case, hepatic revascularization was particularly challenging, but was successfully accomplished by left external iliac-hepatic arterial bypass. To our knowledge this type of arterial bypass has never been described so far in the English literature and its description may be important for surgeons dealing with advanced pancreatic cancer. (C) 2009 Elsevier Ltd. All rights reserved.

Gas gap heat switch for CryoFree project

Cryogen-free superconducting magnet systems have become popular during the last two decades for the simple reason that with the use of liquid helium is rather cumbersome and is a scarce resource. Some available CFMS uses a mechanical cryocooler as cold source of the superconductor magnet. However, the cooling of the sample holder is still made through an open circuit of helium. A thermal management of a completely cryogen-free system is possible to be implemented by using a controlled gas gap heat switch (GGHS) between the cryocooler and the variable temperature insert (VTI). This way it would eliminate the helium open circuit. Heat switches are devices that allow to toggle between two distinct thermal states (ON and OFF state). Several cryogenic applications need good thermal contact and a good thermal insulation at different stages of operation. A versatile GGHS was designed and built with a 100 mm gap and tested with helium as exchange gas. An analytic thermal model was developed and a good agreement with the experimental data was obtained. The device was tested on a crycooler at 4 to 80 K ranges. A 285 mW/K thermal conductance was measured at ON state and 0.09 mW/K at OFF. 3000 ON/OFF thermal conductance ratio was obtained at 4 K with helium.

Fontan Operation and the Cavopulmonary Technique: Immediate and Late Results According to the Presence of Atrial Fenestration

OBJECTIVE: To compare immediate and late results in patients with or without fenestration who underwent cavopulmonary anastomosis so that we could assess the efficiency of the technique. METHODS: Sixty-two patients underwent surgery between 1988 and 1999, 41 with fenestration (group I -G I) and 21 without fenestration (group II -G II). Tricuspid atresia was prevalent in group I (23-56%) and single ventricle was prevalent in group II (14-66%). Mean ages at the time of operation were 7.3 years in group I and 7.6 in group II. At late follow-up, mean ages were 10.6 years in group I and 12.8 years in group II. RESULTS: Immediate and late mortality were 7.3% in G-I and 4.7% in G-II. Significant pleural effusion occurred in 41.4% of G-I patients and in 23.8% of G-II patients. Significant pericardial effusion occurred in 29.2% and 14.2%, respectively, in groups I and II. Central venous pressure was greater in G-II, 17.7 cm in H2O, as opposed to 15 cm in G-I. Hospital stay was similar between the groups, 26.3 and 21.8 days, respectively. Cyanosis and arterial insaturation occurred in 5 patients, and 4 patients were in functional class II, all from G-I. At late follow-up, 58 (93.5%) were in functional class I. Sinus rhythm was present in 94%, and pulmonary perfusion was similar in both groups. Eleven patients who underwent spirometry had good tolerance to physical effort. CONCLUSION: Atrial fenestration did not improve the immediate or late follow-up of patients who underwent cavopulmonary anastomosis, and is, therefore, dispensable.

Late Clinical Outcomes of the Fontan Operation in Patients with Tricuspid Atresia

OBJECTIVE: Evaluation of the long-term clinical results of the Fontan operation in patients with tricuspid atresia. METHODS: A retrospective analysis was made at the Instituto de Cardiologia do Rio Grande do Sul (Institute of Cardiology of Rio Grande do Sul), from August 1980 through January 2000, of 25 patients with a long-term follow-up, out of a series of 36 patients who underwent the Fontan operation or one of its variants due to tricuspid atresia. Their mean age at surgery was 5.4±3.1 years, and their mean weight was 15.8±6.1 kg, the majority of them (63.9%) being males. Four patients underwent the classical Fontan operation, 12 the Kreutzer variant, 6 the Björk variant, 9 total cavopulmonary shunt with a fenestrated tube, and 5 total cavopulmonary shunt with a nonfenestrated tube. RESULTS: The patients were followed-up on an outpatient basis, with a mean long-term survival time of 5.5±4.2 years (50 days to 17.8 years) and a late mortality rate of 8%. Arterial saturation increased from 77.2±18.8% in the preoperative period to 91±6.7% upon the last outpatient visit (p>0.05). At the final check, most (67%) patients were asymptomatic and 87% could tolerate exercise. Ten (40%) patients experienced some kind of complication during the long-term follow-up, such as cardiac arrhythmia, cyanosis, protein-losing enteropathy, neurological events, right heart failure, intolerance to exercise and reoperation. CONCLUSION: The results indicate that, once the immediate postoperative period is over, during which the adaptations to the new circulatory physiology occur, the evolution of patients with tricuspid atresia who underwent the Fontan operation is satisfactory, in spite of a low, yet significant, morbidity.

Survival and Quality of Life among Patients with Severe Lower Extremity Peripheral Arterial Disease

Lower extremity peripheral arterial disease (PAD) is associated with decreased functional status, diminished quality of life (QoL), amputation, myocardial infarction, stroke, and death. Nevertheless, public awareness of PAD as a morbid and mortal disease is low. The aim of this study was to assess the incidence of major lower extremity amputation due to PAD, the extent of reamputations, and survival after major lower extremity amputation (LEA) in a population based PAD patient cohort. Furthermore, the aim was to assess the functional capacity in patients with LEA, and the QoL after lower extremity revascularization and major amputation. All 210 amputees due to PAD in 1998–2002 and all 519 revascularized patients in 1998–2003 were explored. 59 amputees alive in 2004 were interviewed using a structured questionnaire of QoL. Two of each amputee age-, gender- and domicile-matched controls filled in and returned postal self-administered QoL questionnaire as well as 231 revascularized PAD patients (the amount of these patients who engaged themselves to the study), and one control person for each patient completed postal self-administered QoL questionnaire. The incidence rate of major LEA was 24.1/100 000 person-years and it was considerably high during the years studied. The one-month mortality rate was 21%, 52% at one-year, and the overall mortality rate was 80%. When comparing the one-year mortality risk of amputees, LEAs were associated with a 7.4-fold annual mortality risk compared with the reference population in Turku. Twenty-two patients (10%) had ipsilateral transversions from BK to AK amputation. Fifty patients (24%) ended up with a contralateral major LEA within two to four amputation operations. Three bilateral amputations were performed at the first major LEA operation. Of the 51 survivors returning home after their first major LEA, 36 (71%) received a prosthesis; (16/36, 44%) and were able to walk both in- and outdoors. Of the 68 patients who were discharged to institutional care, three (4%) had a prosthesis one year after LEA. Both amputees and revascularized patients had poor physical functioning and significantly more depressive symptoms than their controls. Depressive symptoms were more common in the institutionalized amputees than the home-dwelling amputees. The surviving amputees and their controls had similar life satisfaction. The amputees felt themselves satisfied and contented, whether or not they lived in long-term care or at home. PAD patients who had undergone revascularizations had poorer QoL than their controls. The revascularized patients’ responses on their perceived physical functioning gave an impression that these patients are in a declining life cycle and that revascularizations, even when successful, may not be sufficient to improve the overall function. It is possible that addressing rehabilitation issues earlier in the care may produce a more positive functional outcome. Depressive symptoms should be recognized and thoroughly considered at the same time the patients are recovering from their revascularization operation. Also primary care should develop proper follow-up, and community organizations should have exercise groups for those who are able to return home, since they very often live alone. In rehabilitation programs we should consider not only physical disability assessment but also QoL.

Minimizing Conducted RF-Emissions in Switch Mode Power Supplies Using Spread-Spectrum Techniques

Switching power supplies are usually implemented with a control circuitry that uses constant clock frequency turning the power semiconductor switches on and off. A drawback of this customary operating principle is that the switching frequency and harmonic frequencies are present in both the conducted and radiated EMI spectrum of the power converter. Various variable-frequency techniques have been introduced during the last decade to overcome the EMC problem. The main objective of this study was to compare the EMI and steady-state performance of a switch mode power supply with different spread-spectrum/variable-frequency methods. Another goal was to find out suitable tools for the variable-frequency EMI analysis. This thesis can be divided into three main parts: Firstly, some aspects of spectral estimation and measurement are presented. Secondly, selected spread spectrum generation techniques are presented with simulations and background information. Finally, simulations and prototype measurements from the EMC and the steady-state performance are carried out in the last part of this work. Combination of the autocorrelation function, the Welch spectrum estimate and the spectrogram were used as a substitute for ordinary Fourier methods in the EMC analysis. It was also shown that the switching function can be used in preliminary EMC analysis of a SMPS and the spectrum and autocorrelation sequence of a switching function correlates with the final EMI spectrum. This work is based on numerous simulations and measurements made with the prototype. All these simulations and measurements are made with the boost DC/DC converter. Four different variable-frequency modulation techniques in six different configurations were analyzed and the EMI performance was compared to the constant frequency operation. Output voltage and input current waveforms were also analyzed in time domain to see the effect of the spread spectrum operation on these quantities. According to the results presented in this work, spread spectrum modulation can be utilized in power converter for EMI mitigation. The results from steady-state voltage measurements show, that the variable-frequency operation of the SMPS has effect on the voltage ripple, but the ripple measured from the prototype is still acceptable in some applications. Both current and voltage ripple can be controlled with proper main circuit and controller design.

A unity power factor multiple isolated outputs switching mode power supply using a single switch

The authors present an offline switching power supply with multiple isolated outputs and unity power factor with the use of only one power processing stage, based on the DC-DC SEPIC (single ended primary inductance converter) modulated by variable hysteresis current control. The principle of operation, the theoretical analysis, the design procedure, an example, and simulation results are presented. A laboratory prototype, rated at 160 W, operating at a maximum switching frequency of 100 kHz, with isolated outputs rated at +5 V/15 A -5 V/1 A, +12 V/6 A and -12 V/1 A, has been built given an input power factor near unity.

Switch allocation problems in power distribution systems

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Oxidative stress precedes peak systemic inflammatory response in pediatric patients undergoing cardiopulmonary bypass operation

Oxidative stress seems to contribute to cardiopulmonary bypass (CPB)-related postoperative complications. Pediatric patients are particularly prone to these complications. With this in mind, we measured oxidative stress markers in blood plasma of 20 children undergoing elective heart surgery before, during, and up to 48 h after cessation of CPB, along with inflammatory parameters and full analysis of iron status. Ascorbate levels were decreased by approximately 50% (P < 0.001) at the time of aorta cross-clamp removal (or pump switch-off in 4 patients with partial CPB), and associated with corresponding increases in dehydroascorbate (P < 0.001, r = -0.80) and malondialdehyde (P < 0.01, r = -0.59). In contrast to the immediate oxidative response, peak levels of IL-6 and IL-8 were not observed until 3-12 h after CPB cessation. The early loss of ascorbate correlated with duration of CPB (P < 0.002, r = 0.72), plasma hemoglobin after cross-clamp removal (P < 0.001, r = 0.70), and IL-6 and IL-8 levels at 24 and 48 h after CPB (P < 0.01), but not with postoperative lactate levels, strongly suggesting that hemolysis, and not inflammation or ischemia, was the main cause of early oxidative stress. The correlation of ventilation time with early changes in ascorbate (P < 0.02, r = 0.55), plasma hemoglobin (P < 0.01, r = 0.60), and malondialdehyde (P < 0.02, r = 0.54) suggests that hemolysis-induced oxidative stress may be an underlying cause of CPB-associated pulmonary dysfunction. Optimization of surgical procedures or therapeutic intervention that minimize hemolysis (e.g., off-pump surgery) or the resultant oxidative stress (e.g., antioxidant treatment) should be considered as possible strategies to lower the rate of postoperative complications in pediatric CPB.

Meristem-Specific Suppression of Mitosis and a Global Switch in Gene Expression in the Root Cap of Pea by Endogenous Signals1

Two functionally distinct sets of meristematic cells exist within root tips of pea (Pisum sativum): the root apical meristem, which gives rise to the body of the root; and the root cap meristem, which gives rise to cells that differentiate progressively through the cap and separate ultimately from its periphery as border cells. When a specific number of border cells has accumulated on the root cap periphery, mitosis within the root cap meristem, but not the apical meristem, is suppressed. When border cells are removed by immersion of the root tip in water, a transient induction of mitosis in the root cap meristem can be detected starting within 5 min. A corresponding switch in gene expression throughout the root cap occurs in parallel with the increase in mitosis, and new border cells begin to separate from the root cap periphery within 1 h. The induction of renewed border cell production is inhibited by incubating root tips in extracellular material released from border cells. The results are consistent with the hypothesis that operation of the root cap meristem and consequent turnover of the root cap is self-regulated by a signal from border cells.

Reserva de recursos MSRP para o switch de tempo-real HaRTES

Os mecanismos e técnicas do domínio de Tempo-Real são utilizados quando existe a necessidade de um sistema, seja este um sistema embutido ou de grandes dimensões, possuir determinadas características que assegurem a qualidade de serviço do sistema. Os Sistemas de Tempo-Real definem-se assim como sistemas que possuem restrições temporais rigorosas, que necessitam de apresentar altos níveis de fiabilidade de forma a garantir em todas as instâncias o funcionamento atempado do sistema. Devido à crescente complexidade dos sistemas embutidos, empregam-se frequentemente arquiteturas distribuídas, onde cada módulo é normalmente responsável por uma única função. Nestes casos existe a necessidade de haver um meio de comunicação entre estes, de forma a poderem comunicar entre si e cumprir a funcionalidade desejadas. Devido à sua elevada capacidade e baixo custo a tecnologia Ethernet tem vindo a ser alvo de estudo, com o objetivo de a tornar num meio de comunicação com a qualidade de serviço característica dos sistemas de tempo-real. Como resposta a esta necessidade surgiu na Universidade de Aveiro, o Switch HaRTES, o qual possui a capacidade de gerir os seus recursos dinamicamente, de modo a fornecer à rede onde é aplicado garantias de Tempo-Real. No entanto, para uma arquitetura de rede ser capaz de fornecer aos seus nós garantias de qualidade serviço, é necessário que exista uma especificação do fluxo, um correto encaminhamento de tráfego, reserva de recursos, controlo de admissão e um escalonamento de pacotes. Infelizmente, o Switch HaRTES apesar de possuir todas estas características, não suporta protocolos standards. Neste documento é apresentado então o trabalho que foi desenvolvido para a integração do protocolo SRP no Switch HaRTES.