RESUMEN
Defect engineering of two-dimensional (2D) materials offers an unprecedented route to increase their functionality and broaden their applicability. In light of the recent synthesis of the 2D Silicon Carbide (SiC), a deep understanding of the effect of defects on the physical and chemical properties of this new SiC allotrope becomes highly desirable. This study investigates 585 extended line defects (ELDs) in hexagonal SiC considering three types of interstitial atom pairs (SiSi-, SiC-, and CC-ELD) and using computational methods like Density Functional Theory, Born-Oppenheimer Molecular Dynamics, and Kinetic Monte-Carlo (KMC). Results show that the formation of all ELD systems is endothermic, with the CC-ELD structure showing the highest stability at 300 K. To further characterize the ELDs, simulated scanning tunneling microscopy (STM) is employed, and successfully allow identify and distinguish the three types of ELDs. Although pristine SiC has a direct band gap of 2.48 eV, the presence of ELDs introduces mid-gap states derived from the pz orbitals at the defect sites. Furthermore, our findings reveal that the ELD region displays enhanced reactivity towards hydrogen adsorption, which was confirmed by KMC simulations. Overall, this research provides valuable insights into the structural, electronic, and reactivity properties of ELDs in hexagonal SiC monolayers and paves the way for potential applications in areas such as catalysis, optoelectronics, and surface science.
RESUMEN
High-performance nanosized optoelectronic devices based on van der Waals (vdW) heterostructures have significant potential for use in a variety of applications. However, the investigation of nanoribbon-based vdW heterostructures are still mostly unexplored. In this study, based on first-principles calculations, we demonstrate that a Sb2S3/Sb2Se3 vdW heterostructure, which is formed by isostructural nanoribbons of stibnite (Sb2S3) and antimonselite (Sb2Se3), possesses a direct band gap with a typical type-II band alignment, which is suitable for optoelectronics and solar energy conversion. Optical absorption spectra show broad profiles in the visible and UV ranges for all of the studied configurations, indicating their suitability for photodevices. Additionally, in 1D nanoribbons, we see sharp peaks corresponding to strongly bound excitons in a fashion similar to that of other quasi-1D systems. The Sb2S3/Sb2Se3 heterostructure is predicted to exhibit a remarkable power conversion efficiency (PCE) of 28.2%, positioning it competitively alongside other extensively studied two-dimensional (2D) heterostructures.
RESUMEN
Franckeite is a natural superlattice composed of two alternating layers of different composition which has shown potential for optoelectronic applications. In part, the interest in franckeite lies in its layered nature which makes it easy to exfoliate into very thin heterostructures. Not surprisingly, its chemical composition and lattice structure are so complex that franckeite has escaped screening protocols and high-throughput searches of materials with nontrivial topological properties. On the basis of density functional theory calculations, we predict a quantum phase transition originating from stoichiometric changes in one of franckeite composing layers (the quasihexagonal one). While for a large concentration of Sb, franckeite is a sequence of type-II semiconductor heterojunctions, for a large concentration of Sn, these turn into type-III, much alike InAs/GaSb artificial heterojunctions, and franckeite becomes a strong topological insulator. Transmission electron microscopy observations confirm that such a phase transition may actually occur in nature.
Asunto(s)
Semiconductores , Microscopía Electrónica de Transmisión , Transición de FaseRESUMEN
In this work, we have investigated the effects of in-plane mechanical strains on the electronic properties of single-layer α-In2Se3 by means of density functional theory (DFT) calculations. Our findings reveal that this system exhibits a semiconductor character with an indirect band gap in the ground state, with a compressive biaxial strain leading to an indirect to direct band gap transition. Remarkably, along with the band gap transition, the system displays promising capability to produce hydrogen gas from a visible light photocatalytic water splitting process.
RESUMEN
The pathophysiological mechanisms associated with the effects of red blood cell (RBC) transfusion on cardiopulmonary function and inflammation are unclear. We developed an experimental model of homologous 14-days stored RBC transfusion in hypovolemic swine to evaluate the short-term effects of transfusion on cardiopulmonary system and inflammation. Sixteen healthy male anesthetized swine (68±3.3 kg) were submitted to controlled hemorrhage (25% of blood volume). Two units of non-filtered RBC from each animal were stored under blood bank conditions for 14 days. After 30 min of hypovolemia, the control group (n=8) received an infusion of lactated Ringer's solution (three times the removed volume). The transfusion group (n=8) received two units of homologous 14-days stored RBC and lactated Ringer's solution in a volume that was three times the difference between blood removed and blood transfusion infused. Both groups were followed up for 6 h after resuscitation with collection of hemodynamic and respiratory data. Cytokines and RNA expression were measured in plasma and lung tissue. Stored RBC transfusion significantly increased mixed oxygen venous saturation and arterial oxygen content. Transfusion was not associated with alterations on pulmonary function. Pulmonary concentrations of cytokines were not different between groups. Gene expression for lung cytokines demonstrated a 2-fold increase in mRNA level for inducible nitric oxide synthase and a 0.5-fold decrease in mRNA content for IL-21 in the transfused group. Thus, stored homologous RBC transfusion in a hypovolemia model improved cardiovascular parameters but did not induce significant effects on microcirculation, pulmonary inflammation and respiratory function up to 6 h after transfusion.
Asunto(s)
Animales , Masculino , Neumonía/fisiopatología , Fenómenos Fisiológicos Respiratorios , Conservación de la Sangre/métodos , Fenómenos Fisiológicos Cardiovasculares , Transfusión de Eritrocitos/métodos , Hipovolemia/terapia , Porcinos , Conservación de la Sangre/efectos adversos , Ensayo de Inmunoadsorción Enzimática , Citocinas/sangre , Resultado del Tratamiento , Transfusión de Eritrocitos/efectos adversos , Modelos Animales de Enfermedad , HemodinámicaRESUMEN
The pathophysiological mechanisms associated with the effects of red blood cell (RBC) transfusion on cardiopulmonary function and inflammation are unclear. We developed an experimental model of homologous 14-days stored RBC transfusion in hypovolemic swine to evaluate the short-term effects of transfusion on cardiopulmonary system and inflammation. Sixteen healthy male anesthetized swine (68±3.3 kg) were submitted to controlled hemorrhage (25% of blood volume). Two units of non-filtered RBC from each animal were stored under blood bank conditions for 14 days. After 30 min of hypovolemia, the control group (n=8) received an infusion of lactated Ringer's solution (three times the removed volume). The transfusion group (n=8) received two units of homologous 14-days stored RBC and lactated Ringer's solution in a volume that was three times the difference between blood removed and blood transfusion infused. Both groups were followed up for 6 h after resuscitation with collection of hemodynamic and respiratory data. Cytokines and RNA expression were measured in plasma and lung tissue. Stored RBC transfusion significantly increased mixed oxygen venous saturation and arterial oxygen content. Transfusion was not associated with alterations on pulmonary function. Pulmonary concentrations of cytokines were not different between groups. Gene expression for lung cytokines demonstrated a 2-fold increase in mRNA level for inducible nitric oxide synthase and a 0.5-fold decrease in mRNA content for IL-21 in the transfused group. Thus, stored homologous RBC transfusion in a hypovolemia model improved cardiovascular parameters but did not induce significant effects on microcirculation, pulmonary inflammation and respiratory function up to 6 h after transfusion.
Asunto(s)
Conservación de la Sangre/métodos , Fenómenos Fisiológicos Cardiovasculares , Transfusión de Eritrocitos/métodos , Hipovolemia/terapia , Neumonía/fisiopatología , Fenómenos Fisiológicos Respiratorios , Animales , Conservación de la Sangre/efectos adversos , Citocinas/sangre , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática , Transfusión de Eritrocitos/efectos adversos , Hemodinámica , Masculino , Oxígeno/metabolismo , Reproducibilidad de los Resultados , Resucitación/métodos , Porcinos , Factores de Tiempo , Resultado del TratamientoRESUMEN
The prospect of carbon-based magnetic materials is of immense fundamental and practical importance, and information on atomic-scale features is required for a better understanding of the mechanisms leading to carbon magnetism. Here we report the first direct detection of the microscopic magnetic field produced at (13)C nuclei in a ferromagnetic carbon material by zero-field nuclear magnetic resonance (NMR). Electronic structure calculations carried out in nanosized model systems with different classes of structural defects show a similar range of magnetic field values (18-21 T) for all investigated systems, in agreement with the NMR experiments. Our results are strong evidence of the intrinsic nature of defect-induced magnetism in magnetic carbons and establish the magnitude of the hyperfine magnetic field created in the neighbourhood of the defects that lead to magnetic order in these materials.
Asunto(s)
Anticuerpos Antiprotozoarios/sangre , Donantes de Sangre , Malaria/prevención & control , Plasmodium/inmunología , Reacción a la Transfusión , Antígenos de Protozoos/inmunología , Brasil/epidemiología , Portador Sano/sangre , Portador Sano/diagnóstico , ADN Protozoario/sangre , Enfermedades Endémicas , Ensayo de Inmunoadsorción Enzimática , Europa (Continente)/epidemiología , Técnica del Anticuerpo Fluorescente Indirecta , Humanos , Israel/epidemiología , Malaria/sangre , Malaria/diagnóstico , Malaria/epidemiología , Malaria/transmisión , Nueva Zelanda/epidemiología , Técnicas de Amplificación de Ácido Nucleico , Estados Unidos/epidemiologíaRESUMEN
BACKGROUND AND OBJECTIVES: The aim of this work was to study the incidence of transfusion-induced platelet-reactive antibodies in a selective patient population and evaluate different methodologies for platelet antibody screening (PAS). MATERIALS AND METHODS: The patients were retrospectively selected and divided into three separate groups: haematological malignancies (Group 1: n = 33); cardiac and orthopaedic patients (Group 2: n = 31) and a control group (Group 3: n = 23) selected with the same diagnoses of Group 2. PRE- and POST-transfusion samples were tested for PAS by the following tests: PIFT (platelet immunofluorescence test), MAIPA (monoclonal antibody immobilization of platelet antigen), Flow PRA(R) and LCT (lymphocytotoxicity test). RESULTS: There was not a 100% concordance among the methodologies used. PIFT, MAIPA and Flow PRA presented very similar results whereas that of LCT differed from the other methods. A high rate of positive results (32%) was found in the PRE samples followed by an increase of almost 50% after blood transfusion (POST samples: 42.5% of positivity), but there was a statistical difference (P < 0.05) between the PRE and POST transfusion sample only for the Flow PRA(R) technique tested on Group 2. Human leucocyte antigen (HLA) class I antibodies were present on 97.4% of POST positive samples, 5.4% presented anti-human platelet antigen (HPA)-1b antibodies and 8.1% presented a mix of pan-reactive antibodies against glycoprotein IIbIIIa, IaIIa and IbIX. CONCLUSIONS: Blood transfusion did not increase the rate of alloimmunization in our haematological patients (Group 1); however, the patients were already admitted with a high rate of alloimmunization (12%). Group 2 patients are being immunized and the impact of this procedure remains to be studied as these patients may eventually undergo further hospitalization and receive more blood transfusion.
Asunto(s)
Antígenos de Plaqueta Humana/inmunología , Antígenos HLA/inmunología , Isoanticuerpos/sangre , Reacción a la Transfusión , Anciano , Femenino , Humanos , Isoanticuerpos/inmunología , Masculino , Persona de Mediana Edad , Estudios RetrospectivosAsunto(s)
Patógenos Transmitidos por la Sangre , Enfermedades Parasitarias/epidemiología , Enfermedades Parasitarias/transmisión , Reacción a la Transfusión , Babesiosis/epidemiología , Babesiosis/transmisión , Humanos , Leishmaniasis/epidemiología , Leishmaniasis/transmisión , Malaria/epidemiología , Malaria/transmisión , Enfermedades Parasitarias/sangre , Enfermedades Parasitarias/prevención & control , Toxoplasmosis/epidemiología , Toxoplasmosis/transmisión , Tripanosomiasis/epidemiología , Tripanosomiasis/transmisiónAsunto(s)
Donantes de Sangre , Antígenos HLA/inmunología , Isoanticuerpos , Transfusión de Leucocitos/efectos adversos , Síndrome de Dificultad Respiratoria/prevención & control , Brasil , Transfusión de Eritrocitos/métodos , Europa (Continente) , Política de Salud , Humanos , Isoanticuerpos/efectos adversos , Isoanticuerpos/sangre , Japón , Leucocitos/efectos de los fármacos , Nueva Zelanda , Síndrome de Dificultad Respiratoria/inmunología , Estados UnidosRESUMEN
FUNDAMENTOS: Ulcera de perna (UP) caracteriza-se por perda do tegumento nas extremidades dos membros inferiores causada geralmente por disfunção vascular. OBJETIVOS: Caracterizar clínica e epidemiologicamente a amostra populacional com UP atendida nos centros de saúde de Juiz de Fora. PACIENTES E MÉTODOS: Submetidos ao protocolo clínico 124 pacientes com UP, de Juiz de Fora e região de janeiro/1999 a agosto/2001. RESULTADOS: A média de idade foi 64 anos, 65,3 por cento do sexo feminino, média de 3,7 indivíduos/família e renda inferior a R$540,00 (86,8 por cento). Associavam-se às úlceras insuficiência venosa (90,3 por cento), hipertensão arterial sistêmica (54 por cento), obesidade (20,2 por cento) e diabetes mellitus (16,1 por cento). A associação insuficiência venosa e hipertensão arterial foi freqüente (43,7 por cento) e significante (p<0.01) para predisposição às úlceras. Foram classificadas como venosas (79 por cento), hipertensivas (15,4 por cento), mistas e outras(5,6 por cento). Acometiam terço distal das pernas (90 por cento), de tamanho grande (5cm) em cerca de 90 por cento da amostra, com médias de 8,7cm e 9,6cm para os eixos vertical e horizontal, respectivamente. Estavam acompanhadas de hipercromia (92,7 por cento), lipodermatoesclerose (68,5 por cento) e varicosidades (66,9 por cento), com duração média de 94,2 meses, e 50 por cento das úlceras eram recidivantes. CONCLUSÕES: Os dados sugerem que a úlcera de perna seja doença crônica significativa na população idosa e de baixa renda de Juiz de Fora e região.
Asunto(s)
Humanos , Femenino , Persona de Mediana Edad , Anciano , Renta , Úlcera de la Pierna , Várices , Anciano , Úlcera de la Pierna/epidemiologíaRESUMEN
BACKGROUND AND OBJECTIVES: The purpose of this article was to describe the experience of screening for human immunodeficiency virus (HIV) p24 antigen (p24Ag) in blood donors, in four Brazilian Blood Banks, and to report the detection of the first window-period donation. MATERIALS AND METHODS: During 61 months (May 96 to June 01), 103 470 consecutive donations were screened for HIV p24Ag using commercially available enzyme-linked immunosorbent assay (ELISA) kits. Testing was carried out in accordance with the instructions supplied with the kits. RESULTS: Fifty-eight repeatedly reactive samples were identified [0.056% of the total; 95% confidence interval (95% CI): 0.042-0.070]. Ten of the 58 were confirmed as p24Ag positive after neutralization (0.010%; 95% CI: 0.004-0.016), nine of the 10 (0.009%; 95% CI: 0.003-0.014) were also HIV antibody positive and only one (0.001%; 95% CI: 0-0.003) was HIV antibody negative. CONCLUSIONS: In this setting the rate of sole p24Ag-positive donations was one in 103 740. This figure corresponds closely with the previously estimated yield of one in 87 796 donations. The yield of HIV p24Ag+ : Ab- has been previously estimated in our centres to be 1 : 87 796 donations, a value similar to that observed in actual practice.
Asunto(s)
Donantes de Sangre , Proteína p24 del Núcleo del VIH/sangre , Tamizaje Masivo/métodos , Bancos de Sangre , Brasil , Ensayo de Inmunoadsorción Enzimática , Infecciones por VIH/diagnóstico , Humanos , Valor Predictivo de las Pruebas , ARN Viral/sangre , Revelación de la VerdadRESUMEN
Many controversies still exist about the timing of leukapheresis procedures for PBSC transplantation. Thirty-nine patients were followed daily by monitoring the absolute PB WBC count and CD34+ cell enumeration prior to apheresis. These determinations were compared with the apheresis cell content (nucleated cells and CD34+ cells yield). There was a highly significant correlation between PB CD34+ cells and apheresis CD34+ cell yield (r = 0.921, p < 0.001). A small but significant correlation was found between the PB WBC count and the apheresis nucleated cell content (r = 0.383, p < 0.001), but no correlation was found between PB WBC count and apheresis CD34+ cell yield (r = -0.065, p = 0.460). A target value of 20 x 10(6) CD34+ cells/L was determined to be the most reliable predictor to collect at least 1.0 x 10(6) CD34+ cells/kg in a single apheresis. Of the 39 patients, 20 could be followed after transplantation, and a good correlation was found for total number of CD34+ cells reinfused and platelet and neutrophil engraftment. No correlation was found for nucleated cells infused and engraftment. CD34+ cell determination is a better predictor than WBC count for timing leukapheresis and is thus recommended for monitoring the quality of the product.
Asunto(s)
Antígenos CD34/análisis , Recuento de Células Sanguíneas , Células Madre Hematopoyéticas , Adolescente , Adulto , Anciano , Antígenos CD34/inmunología , Niño , Preescolar , Femenino , Trasplante de Células Madre Hematopoyéticas , Humanos , Leucaféresis , Recuento de Leucocitos , Leucocitos , Masculino , Persona de Mediana Edad , Neoplasias/sangre , Neutrófilos/citología , Recuento de PlaquetasRESUMEN
Desde 1970 vem ocorrendo crescimento na utilização de ossos alogênicos em vários procedimentos ortopédicos, resultando na criação de bancos de ossos no mundo todo. Com o propósito de minimizar a morbidade nos receptores de ossos e padronizar procedimento operacionais para banco de ossos, os autores consideram necessário e fundamental estabelecer normas e critérios para regulamentar a doação de ossos. Seu objetivo é propor uma padronização para procedimentos operacionais em banco de ossos no Brasil. Com a finalidade de padronizar um manual operacional, vários manuais de padronização provenientes de instituições internacionais foram consultados, juntamente com a Portaria 1.376 do Ministério da Saúde (1993), por ser esta a referência concernente à doação de sangue no Brasil. Dessa maneira, parece ser plausível a adaptação de regulamentos internacionais para banco de ossos à legislação brasileira. Um manual de procedimentos operacionais em banco de ossos foi desenvolvido com o objetivo de padronizar os critérios para a retirada, identificação, processamento, estoque e liberação do material doado. Nesse manual também estão contidos os testes sorológicos mínimos para a investigação de doenças infecciosas e testes microbiológicos para o descarte de material contaminado. O banco de ossos necessita de um programa de controle de qualidade similar ao do banco de sangue. É recomendado que o banco de ossos seja gerenciado pelo banco de sangue, por sua experiência gerencial e sua estrutura operacional adequada para o manuseio do material doado.
Asunto(s)
Humanos , Masculino , Femenino , Adulto , Persona de Mediana Edad , Bancos de Huesos , Trasplante Homólogo/normas , Bancos de Huesos , Protocolos Clínicos , Obtención de Tejidos y ÓrganosRESUMEN
Transfusion-transmitted Chagas' disease has been recognized since 1952. Until recently, no cases were reported outside of Latin America. However, emigration during the past 20 years expanded its transfusional geographic borders to North America. Trypanosoma cruzi-infected donors usually are asymptomatic, often for a lifetime. This situation complicates donor screening, particularly in regions where blood bank personnel are not familiar with the risk factors and natural history of this transfusion-transmitted infection. This review addresses the main aspects of epidemiology, risks of infection, clinical symptoms in donors and recipients, preventive measures, and blood donor screening to prevent transfusion-transmitted Chagas' disease.
Asunto(s)
Enfermedad de Chagas/transmisión , Reacción a la Transfusión , Donantes de Sangre , Enfermedad de Chagas/epidemiología , Enfermedad de Chagas/inmunología , Humanos , Tamizaje Masivo/métodos , América del Norte/epidemiología , Prevalencia , Factores de Riesgo , América del Sur/epidemiologíaRESUMEN
As participants of the "III International Workshop on Monoclonal Antibodies against Human Red Blood Cells and Related Antigens", we tested 43 RH monoclonal antibodies by the flow cytometry technique. Besides the anti-D antibodies (not included in this paper), we tested the following antibodies: three (3) anti-C; one (1) anti-Cw; six (6) anti-c; eight (8) anti-E; three (3) anti-e; two (2) anti-G; one (1) anti-CcEe (total = 24 antibodies). These antibodies (from different lab sources) were tested against antigen positive cells (homozygous or heterozygous) and antigen negative cells. When available, some of them were tested against "rare" phenotypes like ryr, r' 'Gr, rGr, R2Rz. All the three anti-C tested, showed poor discrimination between positive and negative cells; from the six anti-c tested, only three had good results (Workshop n degree 18, 20, 21) with a superior performance of one of them (Workshop n degree 18). From the eight anti-E tested, we found two (Workshop n degree 139 and 153) with good performance; all the three anti-e were non reactive; the two anti-G failed to react with r'r red cells; the anti-Cw reacted better with R1wr cells than R1wR1; and the anti-CcEe antibody showed good results with all the phenotypes tested. From the 24 antibodies tested, we found six (25%) antibodies with a good performance.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Eritrocitos/inmunología , Citometría de Flujo , Sistema del Grupo Sanguíneo Rh-Hr/inmunología , HumanosRESUMEN
O objetivo do presente artigo é revisar os aspectos do mieloma múltiplo, uma neoplasia de plasmócitos, envolvidos na produçäo de imunoglobulina monoclonal. Abordam-se conceitos etiológicos, patológicos, clínicos e terapêuticos, enfatizando-se os mais recentes avanços no conhecimento desta enfermidade
Asunto(s)
Humanos , Mieloma Múltiple , Mieloma Múltiple/complicaciones , Mieloma Múltiple/diagnóstico , Mieloma Múltiple/terapiaRESUMEN
Specific serological screening tests for Trypanosoma-cruzi-infected donors are not yet available and thus not routinely performed in North America. With the recent increase of Latin-American immigration to North America and Europe, there is a risk of transmission by blood products. In this study, we evaluated the possibility whether any of the serological screening tests currently recommended by the AABB could be used as a surrogate marker for this protozoarium. A group of 26,365 blood donors (male = 21,053 and female = 5,312) was analysed for the correlation of T. cruzi antibodies (TcAb) with other serological markers (HIV, HBsAg, ALT, HTLV-I/II, HCV, Anti-HBc, syphilis and unexpected hemoglobins other than A1, A2 and F). Association could be demonstrated only between syphilis and TcAb in the female group (p = 0.005), but the low number of donors found with this association (n = 4) renders the effect of this correlation very small. A higher prevalence of TcAb was found in older age groups, with even gender distribution (p < 0.05), however, donors aged more than 54 years also represent a minority of the donor pool (4.83%) and the detection of positive donors in this age group also has a minor preventive effect on transfusion-transmitted Chagas disease. We conclude that when infected blood donors must be detected, specific serological screening for TcAb is essential and that currently no surrogate marker can be considered for detecting T. cruzi-infected blood donors.