Optimization Criteria and Efficiency of a Thermoelectric Generator.

The efficiency of a thermoelectric generator model under maximum conditions is presented for two optimization criteria proposed under the context of finite-time thermodynamics, namely, the efficient power criterion and the Omega function, where this last function represents a trade-off between useful and lost energy. The results are compared with the performance of the device at maximum power output. A macroscopic thermoelectric generator (TEG) model with three possible sources of irreversibilities is considered: (i) the electric resistance R for the Joule heating, (ii) the thermal conductances Kh and Kc of the heat exchangers between the thermal baths and the TEG, and (iii) the internal thermal conductance K for heat leakage. In particular, two configurations of the macroscopic TEG are studied: the so-called exoreversible case and the endoreversible limit. It shows that for both TEG configurations, the efficiency at maximum Omega function is always greater than that obtained in conditions of maximum efficient power, and this in turn is greater than that of the maximum power regime.

Dendritic Immunotherapy Improvement for an Optimal Control Murine Model.

Therapeutic protocols in immunotherapy are usually proposed following the intuition and experience of the therapist. In order to deduce such protocols mathematical modeling, optimal control and simulations are used instead of the therapist's experience. Clinical efficacy of dendritic cell (DC) vaccines to cancer treatment is still unclear, since dendritic cells face several obstacles in the host environment, such as immunosuppression and poor transference to the lymph nodes reducing the vaccine effect. In view of that, we have created a mathematical murine model to measure the effects of dendritic cell injections admitting such obstacles. In addition, the model considers a therapy given by bolus injections of small duration as opposed to a continual dose. Doses timing defines the therapeutic protocols, which in turn are improved to minimize the tumor mass by an optimal control algorithm. We intend to supplement therapist's experience and intuition in the protocol's implementation. Experimental results made on mice infected with melanoma with and without therapy agree with the model. It is shown that the dendritic cells' percentage that manages to reach the lymph nodes has a crucial impact on the therapy outcome. This suggests that efforts in finding better methods to deliver DC vaccines should be pursued.

Pretransplant CD28 Biomarker (Levels of Expression and Quantification of Molecules per Cell) in Peripheral CD4+ T Cells Predicts Acute Rejection Episodes in Liver and Kidney Recipients.

BACKGROUND: Acute rejection (AR) remains a significant cause of graft loss. Better approaches to predict AR are being investigated. Surface CD28 protein is essential for T-cell proliferation and survival as well as cytokine production. PATIENTS AND METHODS: Pretransplant CD4+CD28+ peripheral T cells were examined in 30 liver recipients (LRs) and 31 kidney recipients (KRs) by flow cytometry. RESULTS: Pretransplant CD4+CD28+ T cells in LRs were significantly lower in rejectors than nonrejectors (P = .002). Furthermore, the total number of CD28 molecules per cell in LRs (P = .02) as well as KRs (P = .047) was significantly lower in rejectors than nonrejectors. The healthy group did not display differences when compared with patients with end-stage liver disease or renal failure; however, stratification analysis displayed higher levels of CD4+CD28+ when compared with rejected LRs (P = .04) but not KRs. CD28 levels <41.94% were able to discriminate LRs at high risk of AR (P = .003). Similarly, a total number of CD28 molecules ≤8359 (P = .031) in LRs and ≤7669 (P = .046) in KRs correlated with high risk of AR. CONCLUSION: The preliminary results presented herein exhibit a fast and noninvasive method that assists clinicians to prevent AR by monitoring CD4+CD28+ peripheral T cells.

Enhancing dendritic cell immunotherapy for melanoma using a simple mathematical model.

BACKGROUND: The immunotherapy using dendritic cells (DCs) against different varieties of cancer is an approach that has been previously explored which induces a specific immune response. This work presents a mathematical model of DCs immunotherapy for melanoma in mice based on work by Experimental Immunotherapy Laboratory of the Medicine Faculty in the Universidad Autonoma de Mexico (UNAM). METHOD: The model is a five delay differential equation (DDEs) which represents a simplified view of the immunotherapy mechanisms. The mathematical model takes into account the interactions between tumor cells, dendritic cells, naive cytotoxic T lymphocytes cells (inactivated cytotoxic cells), effector cells (cytotoxic T activated cytotoxic cells) and transforming growth factor ß cytokine (T G F-ß). The model is validated comparing the computer simulation results with biological trial results of the immunotherapy developed by the research group of UNAM. RESULTS: The results of the growth of tumor cells obtained by the control immunotherapy simulation show a similar amount of tumor cell population than the biological data of the control immunotherapy. Moreover, comparing the increase of tumor cells obtained from the immunotherapy simulation and the biological data of the immunotherapy applied by the UNAM researchers obtained errors of approximately 10 %. This allowed us to use the model as a framework to test hypothetical treatments. The numerical simulations suggest that by using more doses of DCs and changing the infusion time, the tumor growth decays compared with the current immunotherapy. In addition, a local sensitivity analysis is performed; the results show that the delay in time " τ", the maximal growth rate of tumor "r" and the maximal efficiency of tumor cytotoxic cells rate "aT" are the most sensitive model parameters. CONCLUSION: By using this mathematical model it is possible to simulate the growth of the tumor cells with or without immunotherapy using the infusion protocol of the UNAM researchers, to obtain a good approximation of the biological trials data. It is worth mentioning that by manipulating the different parameters of the model the effectiveness of the immunotherapy may increase. This last suggests that different protocols could be implemented by the Immunotherapy Laboratory of UNAM in order to improve their results.

Complement component C6 deficiency in a Spanish family: implications for clinical and molecular diagnosis.

Complement component C6 deficiency is a genetic disease presenting as increased susceptibility to invasive Neisseria meningitidis infections. This disorder has rarely been diagnosed in the Spanish population. In this work we report the immunochemical and molecular characterization of complement C6 deficiency in a Spanish patient showing no detectable functional activity of either the classical or alternative complement pathways and reporting a history of several episodes of meningococcal meningitis. The levels of individual complement components C3, C4, C5, C7, C8 and C9 were within the normal range. However, C6 level was low in the patient's serum as measured by radial immunodiffusion. Exon-specific polymerase chain reaction and sequencing of the C6 gene revealed a previously described homozygous single base deletion in exon 6 (c.821delA), leading to a shift in the reading frame that caused the generation of a downstream stop codon, which, in turn, provoked the truncation of the C6 protein (p.Gln274fs). To our knowledge, this is the first report on the c.821delA mutation in the Spanish population, which has previously only been identified in individuals of African ancestry. Characterization of this mutation was thought interesting in order to elucidate its source and help understand the molecular basis of this uncommon deficiency in our population. Moreover, this report highlights the importance of complement screening in cases of repeated meningococcal infections in order to establish its involvement and to consider adequate clinical recommendations such as prophylactic antibiotics or meningococcal vaccines and, subsequently, for genetic counselling.

C1q-fixing human leukocyte antigen assay in immunized renal patients: correlation between Luminex SAB-C1q and SAB-IgG.

BACKGROUND: There is no consensus about the impact of thresholds of complement-fixing antibody assays. Recently, a C1q-SAB assay has been developed to identify complement-fixing HLA antibodies with high sensitivity and specificity. Our aim was to determine the correlation between IgG single antigens beads (SAB) and C1q-SAB assay results among patients on the renal waiting list. PATIENTS AND METHODS: Serum samples from immunized renal waiting list patients as well as negative and positive controls were valided by Luminex (LMX). These sera, which were positive for 166 antibody specificities, were tested for HLA class I in parallel by LMX-IgG and LMX-C1q. RESULTS: Comparison of antibody detection revealed no correlation based on median fluorescent intensity (MFI), levels between the IgG SAB and the C1qSAB assay (P > .05). IgG-positive sera with MFIs as low as 700 were able to fix C1q, whereas other sera with MFIs as high 14,500 did not. Furthermore, there appeared to be disparities in the profiles of class I antigens able to fix C1q-SAB. In our series, only 34% class I IgG SAB antibodies were also C1qSAB+. In several patients, we detected C1qSAB+ against IgGSAB- that was surely due to IgM antibodies. So, the C1qSAB assay detected IgM antibodies that fix complement. CONCLUSION: These data suggested that the C1q-SAB assay could be an important method to evaluate pretransplant virtual crossmatch and to define nonpermitted specificities (C1q-fixing) in kidney transplantation.

Gallbladder selection for histopathological analysis based on a simple method: a prospective comparative study.

INTRODUCTION: After a cholecystectomy, the current and traditional practice is to send each resected gallbladder to the pathologist for analysis. Some reports have suggested the possibility of selecting only those gallbladders that need to be analysed. The purpose of this study was to show a simple method for selecting which gallbladders should be sent to the pathologist. METHODS: A prospective comparative study was carried out. Two 'tests' were performed in 150 patients to detect or rule out gallbladder cancer. The first test included the patient's variables and a macroscopic gallbladder analysis performed by the surgeon (MGAS). The second test was the analysis performed by the pathologist. The results were compared. RESULTS: Of the 150 patients, 132 were women and 18 men; 130 were under 60 years old. One patient had inflammatory bowel disease, seven had changes on ultrasonography and in four cases intra-operative disturbances were observed. During the MGAS, disturbances were found in 30 patients. Eighty-one cases (54%) had at least one or more risk factors for gallbladder cancer.

[Routine preoperative screening of asymptomatic patients: beliefs and attitudes of anesthesiologists in the Canary Islands, Spain]. / Pruebas preoperatorias rutinarias en población asintomática: opiniones y actitudes de los profesionales en Canarias.

OBJECTIVES: To identify factors that explain anesthesiologists' inappropriate use of preoperative tests in asymptomatic patients scheduled for elective surgery. MATERIAL AND METHODS: A validated questionnaire was sent to anesthesiologists at university hospitals in the Canary Islands. Information about preoperative testing patterns and reasons for selecting tests was gathered. RESULTS: The questionnaire was self-administered by 66 anesthesiologists (68% of the total). Scientific knowledge was not the reason why most respondents ordered preoperative tests in asymptomatic individuals. That was the opinion of 95% of anesthesiologists for chest x-rays, 82% for electrocardiograms, and 68% for laboratory tests. Clinical history and a medical examination gave sufficient information for selecting patients in need of specific tests in the opinion of 77.19% of the respondents. Half did not agree that routine electrocardiograms and laboratory tests should be abandoned. The justification for these tests was coverage of medical malpractice liability for 68.42%. Most considered that the need to order preoperative tests in asymptomatic patients increased after age 40. CONCLUSIONS: Although anesthesiologists admit that their request for preoperative tests in asymptomatic individuals is not supported by scientific evidence, the quest for safety and legal protection from the consequences of potential adverse consequences of providing anesthesia affects the selection of preoperative tests for asymptomatic patients.

Pruebas preoperatorias rutinarias en población asintomática: opiniones y actitudes de los profesionales en Canarias / Routine preoperative screening of asymptomatic patients: beliefs and attitudes of anesthesiologists in the Canary Islands, Spain

OBJETIVO: Identificar algunas razones que contribuyen a explicar el uso inapropiado, por parte de los anestesiólogos, de las pruebas preoperatorias en población asintomática que va a ser sometida a cirugía electiva. MATERIAL Y MÉTODO: Un cuestionario validado fue enviado a los anestesiólogos de los hospitales universitarios de Canarias. Se recogió información sobre el patrón de uso y sobre las razones que justifican la selección de pruebas preoperatorias. RESULTADOS: El cuestionario fue autocumplimentado por 66 anestesiólogos (68% del total). Para la mayoría, el conocimiento científico disponible no avala la realización de pruebas preoperatorias en personas asintomáticas. Ésta era la opinión del 95% de los anestesiólogos para la radiografía de tórax; del 82% para el ECG y del 68% para las pruebas de laboratorio. Para el 77,19% de los participantes, la historia clínica y el examen médico suministran suficiente información para seleccionar los pacientes que precisen pruebas específicas. El 50% no está de acuerdo en abandonar la solicitud rutinaria del ECG y de las pruebas de laboratorio. Para el 68,42%, la solicitud de estas pruebas se justifica para cubrir la responsabilidad médico/legal. La mayoría consideran que a partir de los 40 años de edad aumenta la necesidad de realizar pruebas preoperatorias en población asintomática. CONCLUSIONES: Si bien la mayoría de anestesiólogos admiten que la solicitud de pruebas preoperatorias en población asintomática no está respaldada por el conocimiento científico, la búsqueda de seguridad y protección legal frente a las consecuencias adversas potenciales del acto anestésico condiciona la toma de decisiones en la selección de pruebas preoperatorias en población asintomática

OBJECTIVES: To identify factors that explain anesthesiologists' inappropriate use of preoperative tests in asymptomatic patients scheduled for elective surgery. MATERIAL AND METHODS: A validated questionnaire was sent to anesthesiologists at university hospitals in the Canary Islands. Information about preoperative testing patterns and reasons for selecting tests was gathered. RESULTS: The questionnaire was self-administered by 66 anesthesiologists (68% of the total). Scientific know-ledge was not the reason why most respondents ordered preoperative tests in asymptomatic individuals. That was the opinion of 95% of anesthesiologists for chest x-rays, 82% for electrocardiograms, and 68% for laboratory tests. Clinical history and a medical examination gave sufficient information for selecting patients in need of specific tests in the opinion of 77.19% of the respondents. Half did not agree that routine electrocardiograms and laboratory tests should be abandoned. The justification for these tests was coverage of medical mal-practice liability for 68.42%. Most considered that the need to order preoperative tests in asymptomatic patients increased after age 40. CONCLUSIONS: Although anesthesiologists admit that their request for preoperative tests in asymptomatic individuals is not supported by scientific evidence, the quest for safety and legal protection from the consequences of potential adverse consequences of providing anesthesia affects the selection of preoperative tests for asymptomatic patients

[Preoperative testing routines for healthy, asymptomatic patients in the Canary Islands (Spain)]. / Patrón de utilización de pruebas preoperatorias en una población sana y asintomática en Canarias.

OBJECTIVES: To analyze patterns of routine testing before elective/scheduled surgery in healthy/asymptomatic patients classified as ASA I or II according to the American Society of Anesthesiologists. MATERIAL AND METHOD: A questionnaire on the organization of preoperative testing was completed by anesthesiologists at five public hospitals in the Canary Islands. The questionnaire emphasized the most commonly ordered screening procedures, such as chest X-rays, electrocardiograms, laboratory tests and spirometry. RESULTS: Red cell counts were most frequently requested (for 86% of the patients), followed by platelet counts (80%) and blood chemistry (75%) and coagulation studies (72%). Least requested were urine tests and spirometry. The frequencies of electrocardiogram and chest X-ray requests fell between the two extremes, with patient age and the presence of certain indications seeming to affect whether those tests would be ordered or not. The need for such screening was perceived to increase for patients over 40 years of age. The ordering of preoperative tests varied from hospital to hospital and among anesthesiologists at a single site in spite of established protocols. CONCLUSIONS: Hospitals and individual anesthesiologists differ considerably in how they request preoperative tests. The variations can not be explained solely by differing patient needs given that respondents were contemplating only healthy/asymptomatic individuals undergoing relatively simple procedures.

Patrón de utilización de pruebas preoperatorias en una población sana y asintomática en Canarias / Preoperative testing routines for healthy, asymptomatic patients in the Canary Islands (Spain)

OBJETIVO. Evaluar los patrones de uso de las pruebas preoperatorias rutinarias en cirugía electiva y programada a pacientes sanos y asintomáticos, considerados ASA I y II por la Sociedad Americana de Anestesiólogos. MATERIAL Y MÉTODO. Un cuestionario fue cumplimentado por los anestesiólogos de los 5 hospitales públicos de Canarias para conocer cómo se organiza la selección de pruebas preoperatorias. En el cuestionario se prestó especial atención a las pruebas preoperatorias más frecuentemente utilizadas, como la radiografía de tórax, el electrocardiograma, las pruebas de laboratorio y la espirometría. RESULTADOS. De los resultados del cuestionario se desprende que la hematimetría es la determinación que con más frecuencia se efectúa (86 por ciento de los pacientes), seguida por el recuento de plaquetas (80 por ciento), la bioquímica sanguínea (75 por ciento) y el estudio de coagulación (72 por ciento). En el extremo opuesto se sitúa el estudio de orina seguido de la espirometría. La frecuencia intermedia de utilización corresponde al electrocardiograma y a la radiología de tórax, si bien la realización de estas dos pruebas parece estar condicionada por la edad de los pacientes y la concurrencia de indicaciones especiales. El límite de edad a partir del cual se considera que aumenta la necesidad de estas pruebas es situado en los 40 años. Se describen variaciones en la realización de pruebas preoperatorias, tanto entre los anestesiólogos de diferentes hospitales como dentro de cada centro hospitalario, a pesar de la existencia de protocolos en cada uno de ellos. CONCLUSIONES. Existen importantes variaciones en los patrones de uso de las pruebas preoperatorias entre hospitales y entre profesionales que no pueden ser explicadas únicamente por la diferencia de necesidad entre los pacientes, dado que la información requerida afectaba a enfermos sanos y asintomáticos, en los que las intervenciones quirúrgicas previstas eran de bajo grado de complejidad (AU)

The occurrence of disporous Bacillus thuringiensis cells.

Ultrathin sections of sporulating Bacillus thuringiensis were examined in a transmission electron microscope. Less than 1% of the about 2,000 approximately sagittal sections of the bacterial cells examined contained two endospores per cell. This finding clarifies the majority of textbook and research reports (which tend to be ambiguous), contradicts several of the most recent textbook reports, and confirms three unillustrated textbook reports, in relation to the occurrence of disporous bacilli. Electron microscopic evidence of the observation is presented, apparently for the first time.