Modulating redox properties of solid-state ion-conducting materials using microwave irradiation.

The industrial adoption of low-carbon technologies and renewable electricity requires novel tools for electrifying unitary steps and efficient energy storage, such as the catalytic synthesis of valuable chemical carriers. The recently-discovered use of microwaves as an effective reducing agent of solid materials provides a novel framework to improve this chemical-conversion route, thanks to promoting oxygen-vacancy formation and O2-surface exchange at low temperatures. However, many efforts are still required to boost the redox properties and process efficiency. Here, we scrutinise the dynamics and the physicochemical dependencies governing microwave-induced redox transformations on solid-state ion-conducting materials. The reduction is triggered upon a material-dependent induction temperature, leading to a characteristically abrupt rise in electric conductivity. This work reveals that the released O2 yield strongly depends on the material's composition and can be tuned by controlling the gas-environment composition and the intensity of the microwave power. The reduction effect prevails at the grain surface level and, thus, amplifies for fine-grained materials, and this is ascribed to limitations in oxygen-vacancy diffusion across the grain compared to a microwave-enhanced surface evacuation. The precise cyclability and stability of the redox process will enable multiple applications like gas depuration, energy storage, or hydrogen generation in several industrial applications.

Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor.

Nonoxidative methane dehydroaromatization (MDA: 6CH4 ↔ C6H6 + 9H2) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability.

New portable instrument for the measurement of thermal conductivity in gas process conditions.

The development of high temperature gas sensors for the monitoring and determination of thermophysical properties of complex process mixtures at high temperatures faces several problems, related with the materials compatibility, active sensing parts sensitivity, and lifetime. Ceramic/thin metal films based sensors, previously developed for the determination of thermal conductivity of molten materials up to 1200 °C, were redesigned, constructed, and applied for thermal conductivity measuring sensors. Platinum resistance thermometers were also developed using the same technology, to be used in the temperature measurement, which were also constructed and tested. A new data acquisition system for the thermal conductivity sensors, based on a linearization of the transient hot-strip model, including a portable electronic bridge for the measurement of the thermal conductivity in gas process conditions was also developed. The equipment is capable of measuring the thermal conductivity of gaseous phases with an accuracy of 2%-5% up to 840 °C (95% confidence level). The development of sensors up to 1200 °C, present at the core of the combustion chambers, will be done in a near future.

Validation of sentinel lymph node biopsy in breast cancer women N1-N2 with complete axillary response after neoadjuvant chemotherapy. Multicentre study in Tarragona. / Validación de la biopsia selectiva del ganglio centinela en mujeres con cáncer de mama N1-2 con respuesta axilar completa tras la neoadyuvancia. Estudio multicéntrico en la provincia de Tarragona.

INTRODUCTION: The aim of our study was to evaluate sentinel lymph node biopsy as a diagnostic test for assessing the presence of residual metastatic axillary lymph nodes after neoadjuvant chemotherapy, replacing the need for a lymphadenectomy in negative selective lymph node biopsy patients. MATERIAL AND METHODS: A multicentre, diagnostic validation study was conducted in the province of Tarragona, on women with T1-T3, N1-N2 breast cancer, who presented with a complete axillary response after neoadjuvant chemotherapy. Study procedures consisted of performing an selective lymph node biopsy followed by lymphadenectomy. RESULTS: A total of 53 women were included in the study. Surgical detection rate was 90.5% (no sentinel node found in 5 patients). Histopathological analysis of the lymphadenectomy showed complete disease regression of axillary nodes in 35.4% (17/48) of the patients, and residual axillary node involvement in 64.6% (31/48) of them. In lymphadenectomy positive patients, 28 had a positive selective lymph node biopsy (true positive), while 3 had a negative selective lymph node biopsy (false negative). Of the 28 true selective lymph node biopsy positives, the sentinel node was the only positive node in 10 cases. All lymphadenectomy negative cases were selective lymph node biopsy negative. These data yield a sensitivity of 93.5%, a false negative rate of 9.7%, and a global test efficiency of 93.7%. CONCLUSIONS: Selective lymph node biopsy after chemotherapy in patients with a complete axillary response provides valid and reliable information regarding axillary status after neoadjuvant treatment, and might prevent lymphadenectomy in cases with negative selective lymph node biopsy.

Balearic archipelago: three islands, three beta-thalassemia population patterns.

The mutation spectrum of 175 ß-thalassemia (ß-thal) carriers, identified in pilot carrier screening on 22,713 individuals from Balearic Islands (Spain), is reported. The ß(0) CD39 (C>T) mutation is the most frequent (61.1%), followed by ß(+) IVS-I-110 (G>A) (12.0%), ß(+) IVS-I-6 (T>C) and ß(0) IVS-1-1 (G>A) (3.4% both) and eight other rare mutations (2.9-0.6%); with a distinct prevalence and distribution between islands. Minorca shows the highest prevalence in Iberian populations, with a single mutation, CD39 (C>T), present in most ß-thal carriers. Ibiza is the only Western Mediterranean population where the most frequent ß-thal mutation is IVS-I-110 (G>A). These results can be explained by a combination of historical-demographic characteristics together with evolutionary forces such as founder effect, genetic drift and probably selection by malaria. Knowledge of the mutational spectrum in the Balearic Islands will enable to optimize mutation detection strategy for genetic diagnosis of ß-thal in these islands.

Combined investigation of bulk diffusion and surface exchange parameters of silver catalyst coated yttrium-doped BSCF membranes.

The combined effect of minor yttrium doping and silver catalyst deposition on the surface kinetics (k(chem)) and bulk diffusion (D(chem)) of BSCF (Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ)) perovskite membranes was explored using electrical conductivity relaxation (ECR) and validated using oxygen permeation measurements. Yttrium doping of BSCF to form Ba(0.5)Sr(0.5)Co(0.8)Fe(0.175)Y(0.025)O(3-δ) (BSCFY) improved both the surface exchange kinetics and the bulk diffusion by an average of 44% and 177% respectively, supporting improved oxygen permeation measurements. The deposition of a silver catalyst on BSCFY further improved the surface kinetics by 63-450% at intermediate operating temperatures (600-750 °C), and reduced the activation energy from 163 to 90 kJ mol(-1). Interestingly, these improvements did not translate into enhanced oxygen fluxes for the silver coated thicker 0.5 and 1 mm membranes, indicating that the oxygen ion transport was limited by bulk diffusion. However, oxygen permeation measurements on catalyst-coated 0.3 mm-thick membranes yielded improvements of 20-35% in the range 600-900 °C. The silver catalyst was beneficial in overcoming surface kinetic limitations for the thinner 0.3 mm BSCFY membranes, thus suggesting that the critical thickness of BSCFY membranes lies around ∼0.4 mm and validating the ECR measurements.

Support vector machines for predictive modeling in heterogeneous catalysis: a comprehensive introduction and overfitting investigation based on two real applications.

This works provides an introduction to support vector machines (SVMs) for predictive modeling in heterogeneous catalysis, describing step by step the methodology with a highlighting of the points which make such technique an attractive approach. We first investigate linear SVMs, working in detail through a simple example based on experimental data derived from a study aiming at optimizing olefin epoxidation catalysts applying high-throughput experimentation. This case study has been chosen to underline SVM features in a visual manner because of the few catalytic variables investigated. It is shown how SVMs transform original data into another representation space of higher dimensionality. The concepts of Vapnik-Chervonenkis dimension and structural risk minimization are introduced. The SVM methodology is evaluated with a second catalytic application, that is, light paraffin isomerization. Finally, we discuss why SVMs is a strategic method, as compared to other machine learning techniques, such as neural networks or induction trees, and why emphasis is put on the problem of overfitting.

[Complications of craniofacial resection in anterior skull base tumors]. / Complicaciones de la cirugía craneofacial en tumores de base craneal anterior

INTRODUCTION: The development of new radiographic techniques and the refinement of microsurgery and reconstructive surgery have been the responsible of the establishment of craniofacial resection (CFR) as the standard treatment of anterior skull base tumors. Overall complication rates varies from 24-56%, according to a review of recently published series. OBJECTIVES: To describe the complications of CFR in a series of 41 patients and to analyze the management and final outcome. MATERIAL AND METHODS: From 1990 to 2002, 41 patients underwent CFR for tumors involving the anterior cranial base. The extent of the tumor was always assessed with craniofacial CT-scan and MRI. The objective of the surgical treatment was to achieve "on block" removal of the tumor. RESULTS: The average age was 57 years with a male preponderance (63.4%). Squamous cell carcinoma was the most frequent histopathological type of tumor. The tumors were localized in paranasal sinuses in 78% of the cases. Bifrontal craniotomy was performed in 85.4% and unilateral orbitofrontal craniotomy in 14.6% of the cases. The area of facial resection included: ethmoidectomy (60.9%), ethmoido-sphenoidectomy (24.3%), maxillectomy (39%) and orbital exenteration (14.6%). The reconstruction of the floor of the anterior cranial fossa was performed using pedicled pericranial flap (100%), local (34.1%) or microvascular free flaps (21.9%) and split calvarian graft (19.5%). 20 patients (48.7%) developed post-operative complications, CSF leaks (12.1%) and meningitis (7.3%) being the most frequent major complications. The mortality rate was 7.3%. CONCLUSIONS: CFR has become the standard approach for anterior cranial base tumors. Despite its widespread application, the complication's rate ranges between 24-50% and the procedure carries a risk of significant morbidity and even mortality. Improvement of specific aspects of surgical technique and more refined reconstructive methods will decrease the number of complications.

Is the reversed fourth dorsal metacarpal flap reliable?

We have carried out a study to determine if a flap based on vessels in the fourth metacarpal space could be used safely. We studied ten fresh cadaver specimens and used the flap in nine patients. In the anatomical study, we confirmed the presence of a suitable artery in nine out of the ten hands, arising from a piercing artery at the metacarpal bases, running distally under the fascia. The pivot point is located at the metacarpal heads, where the artery anastomoses to palmar branches and dorsal digital branches. In the clinical setting, the flap was reliable in eight patients. There was one case of flap necrosis. The flap seems to be reliable but several technical points are stressed to avoid complications.

[Comparative study of two methods for laryngeal mask insertion]. / Estudio comparativo de dos técnicas de inserción de la mascarilla laríngea.

OBJECTIVE: To compare two ways of inserting laryngeal airway masks: uninflated and partially inflated to 75% of the volume, as recommended by manufacturers. PATIENTS AND METHOD: We studied 60 ASA I-II patients scheduled for outpatient surgery under general anesthesia with numbers 3 or 4 laryngeal masks, after having obtained informed consent from the patients (or parents in the case of minors). The patients were randomly assigned to two groups. In group A the masks were inserted inflated to 75% of volume as recommended by manufacturers, whereas in group B deflated masks were inserted as described by Brain. Anesthesia was standardized for all patients. One patient was withdrawn from the study when a technical error was detected. We recorded the presence of criteria predictive of difficult airway management, systolic and diastolic blood pressures, heart rate at four times (baseline, before and after induction and after insertion of the mask), number of insertion tries, final mask volume needed for adequate ventilation, need for an additional dose of the hypnotic drug and complications. RESULTS: No statistically significant differences between the two insertion methods were found. Difficult airway management criteria were unrelated to difficulty of mask insertion. Correct insertion of an uninflated mask proved impossible in one patient, in whom we were then able to insert an inflated mask. CONCLUSION: No differences were found between inflated insertion and Brain's uninflated insertion technique. We believe that inflated mask insertion might be useful when uninflated insertion proves impossible.

Relationship between flow and incidence of thrombosis in polytetrafluoroethylene vascular grafts in free microvascular flaps in lambs.

We have done an experimental study in lambs in which we investigated the influence of flow rate on free microvascular flaps using polytetrafluoroethylene (PTFE) vascular grafts. We set up five surgical groups in which blood flow was progressively increased through the PTFE vascular graft. In group I (venous autograft) we observed just one vascular thrombosis which was located at the site of the anastomosis. In group II (PTFE 3 x 10 mm) all the microvascular flaps became necrosed after the third postoperative day. In group III (PTFE 3 x 10 mm) necrosis also developed in all cases, but the anastomoses remained permeable no longer than eight days. In group IV (3 x 15 mm) the permeability in the microvascular free flaps was about 40% after 21 days, and in group V (3 x 10 mm) it reached 70%. To match graft flow rates with flap survival we did a regression analysis of flow rates for groups II, III, and V and the corresponding survival periods for the flaps. There was a clear and highly significant relationship (r = 0.717, p = 0.0001). In conclusion, it is necessary to maintain blood flow through the prosthesis at a rate higher than the thrombogenic threshold. When the flow rate in the vessels through the PTFE grafts was higher, the viability of the flaps was better. The ideal surgical technique should always be based on an arteriovenous fistula distal to the PTFE vascular graft. It is necessary to maintain blood flow through a prosthesis at a rate higher than the thrombogenic threshold.

Primary amyloidosis presenting as extensor tenosynovitis.

Primary amyloidosis is a systemic disease. Amyloid arthropathy is an invalidating and uncommon form of presentation, but tenosynovitis is even rarer as the first sign of the disease. We report herein a case of unilateral amyloid deposit in the synovium of the extensor tendons of the hand, which was the first manifestation of a primary amyloidosis.

Transconjunctival herniation of orbital fat.

The authors present 3 patients with subconjunctival fat prolapse treated at their oculoplastic unit. Albeit rare, orbital fat is a well-recognized entity, and is described in the literature as being associated with trauma and surgery. The 3 patients reported herein, however, presented with no history of trauma or surgery. This condition is produced by herniation of the intraconal fat between the conjunctiva and the sclera, presumably due to dehiscence of the Tenon's capsule. Differential diagnosis should be made with lacrimal gland ptosis, lacrimal gland tumors, and lymphoid tumors.

Extensive intra-hospital spread of a methicillin-resistant staphylococcal clone.

OBJECTIVE: Infection by antibiotic-resistant bacteria can pose serious complications to the therapy of cancer patients. The authors introduced DNA fingerprinting techniques for tracking methicillin-resistant Staphylococcus aureus (MRSA) clones recovered at a central cancer hospital of Lisbon (Instituto Português de Oncologia) with the purpose of making an inventory of the MRSA clones endemic during 1995, and compared them with the outbreak-related clones of 1993. DESIGN: A small group (6 strains) of epidemiologically related MRSA isolated during a suspected outbreak in 1993 and all consecutive single-patient isolates of MRSA (34 strains) recovered between January and November of 1995 from infected patients and health care personnel were characterized using DNA probes and pulsed-field gel electrophoresis. RESULTS: The six 1993 strains and more than half of all 1995 isolates, including those recovered from the health care personnel, showed DNA fingerprints characteristic of the "Iberian MRSA," a multiresistant clone widespread in Portuguese and Spanish hospitals. Four patients were infected by another MRSA clone previously seen only in hospitals in Brazil. CONCLUSION: The epidemic Iberian clone was among the index cases involved with the MRSA outbreak in 1993, and this was found to be endemic in a follow-up survey conducted in 1995, colonizing health care personnel and spreading to most hospital wards. A few isolates of another epidemic clone, the Brazilian MRSA, also were detected among 1995 isolates. A better understanding of the mechanism(s) of epidemicity of these rapidly spreading clones is urgently needed.

Reconstruction of pharyngostomes with a modified deltopectoral flap combining endoscopy and tissue expansion.

The problem of pharyngostomic closure is difficult to solve, as evidenced by the large number of techniques described. The authors present the reconstruction of pharyngostomes by using Bakamjian's deltopectoral flap modified by the use of endoscopically introduced expanders for those patients in whom other techniques of choice (such as vascularized free flaps) have failed or are inapplicable either because of previous radiotherapy or because of local conditions. Bakamjian's deltopectoral flap, previously expanded with an expander coated with a partial-thickness skin graft and introduced endoscopically, allowed the authors to lift the flap in one operation to close the pharyngostome. This method provides the two walls of the pharynx (the skin graft as the inner aspect and the skin flap as the outer aspect), and the donor deltopectoral area is covered and epithelialized due to the skin graft. Thus by means of endoscopic expansion we use a nonaggressive technique to increase the surface area of the donor site and to increase its vascularization (delay phenomenon). Because the expander was coated with the graft, the authors were able to cover the anterior wall of the pharyngostome and the donor site in one surgical step.

Effects of involuntary auditory attention on visual task performance and brain activity.

Involuntary attention to auditory stimulus changes during a visual discrimination task was studied with event-related potentials (ERPs) recorded from the human scalp. A repetitive standard tone or an infrequent, slightly higher deviant tone preceded each visual target stimulus. Deviant tones elicited the mismatch negativity and P3a ERP components and caused increases in reaction time and error rate in the visual task indicating involuntary attention to an auditory stimulus change. These effects were observed even when the tones occurred simultaneously with a visual warning stimulus introduced to keep attention focused on the visual task. In the latter condition, involuntary switching of attention away from the visual task also attenuated the N1 ERP component to visual target stimuli preceded by the deviant tone.

Retractor with mobile endoscope.

I have designed two retractors with mobile endoscopes that allow an assistant to lift up the flap and the endoscope. By doing this, the assistant maintains the optical cavity open while the surgeon dissects. There are two models, one with 180-degree lateral swing and the other with motion in all directions (vertical and lateral).

Vascular cryopreservation in microsurgery.

Cyropreservation of blood vessels has been carried out for some decades with variable results. A rabbit model was used to compare cryopreserved femoral artery allografts (n = 12 arteries), fresh autografts (n = 15 arteries), and fresh allografts (n = 16 arteries) at 1 and 3 months postoperatively. Patency rates were highest in the fresh autografts (86.7 percent), followed by the cryopreserved allografts (66.7 percent at 1 month and 83.3 percent at 3 months) and fresh allografts (62.5 percent at 1 month and 75 percent at 3 months). The fresh allografts showed the greatest alterations in endothelial cells and intima and muscle layer, followed by cryopreserved allografts, and then fresh autografts. Changes observed included pseudoendothelium formation, thickened intima, and thinner muscle layer. Cellular infiltrate appeared on the vessel walls only in the cryopreserved allografts (25 percent), but this did not have an effect on vascular patency. Fresh autografts remain the graft of choice for vascular defects, but cryopreserved allografts serve as the most appropriate option when the former are unavailable.

Tissue expansion with endoscopy.

Tissue expansion is a time-honored technique in plastic surgery. However, while it is possible to rectify quite severe problems, the technique is not free of complications (e.g., extrusion) and, moreover, it can be a lengthy procedure, often taking months. Endoscopy is increasingly being used in plastic surgery and has the advantage that large areas can be dissected using only small incisions. However, in endoscopic plastic surgery the main problem is the lack of an optical cavity. This means that special retractors are needed to keep skin and fat tissue lifted. This paper describes a technique for the placement of tissue expanders during endoscopy. Incisions are not made in the area that is to be expanded and, thus, there is no risk of extrusion and tissue expanders can be fully inflated intraoperatively. A further advantage is that the procedure reduces patient discomfort to a minimum.