Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 79
Filtrar
1.
Eur J Surg Oncol ; 50(7): 108395, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38735236

RESUMO

The study of circulating tumor DNA (ctDNA) plays a pivotal role in advancing precision oncology, providing valuable information for individualized patient care and contributing to the ongoing effort to improve cancer diagnosis, treatment, and management. However, its applicability in pseudomyxoma peritonei (PMP) remains unexplored. In this multicenter retrospective study involving 21 PMP patients, we investigated ctDNA presence in peripheral blood using three distinct methodologies. Despite mucinous tumor tissues exhibiting KRAS and GNAS mutations, ctDNA for these mutations was undetectable in blood samples. In this pilot study, circulating tumor DNA was not detected in blood when the tumor harbored mutations of known significance. In the future, a study with a larger sample size is needed to confirm these findings and to determine whether ctDNA could identify patients at risk for early recurrence and/or systemic metastases.


Assuntos
DNA Tumoral Circulante , Neoplasias Peritoneais , Pseudomixoma Peritoneal , Humanos , Pseudomixoma Peritoneal/genética , Pseudomixoma Peritoneal/sangue , Pseudomixoma Peritoneal/patologia , Neoplasias Peritoneais/genética , Neoplasias Peritoneais/secundário , Neoplasias Peritoneais/sangue , DNA Tumoral Circulante/genética , DNA Tumoral Circulante/sangue , Estudos Retrospectivos , Feminino , Pessoa de Meia-Idade , Masculino , Idoso , Subunidades alfa Gs de Proteínas de Ligação ao GTP/genética , Cromograninas/genética , Mutação , Proteínas Proto-Oncogênicas p21(ras)/genética , Projetos Piloto , Adulto
2.
J Neurosci ; 44(10)2024 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-38326038

RESUMO

There has been considerable controversy about pre- versus postsynaptic expression of memory-related long-term potentiation (LTP), with corresponding disputes about underlying mechanisms. We report here an instance in male mice, in which both types of potentiation are expressed but in separate branches of the same hippocampal afferent. Induction of LTP in the dentate gyrus (DG) branch of the lateral perforant path (LPP) reduces paired-pulse facilitation, is blocked by antagonism of cannabinoid receptor type 1, and is not affected by suppression of postsynaptic actin polymerization. These observations are consistent with presynaptic expression. The opposite pattern of results was obtained in the LPP branch that innervates the distal dendrites of CA3: LTP did not reduce paired-pulse facilitation, was unaffected by the cannabinoid receptor blocker, and required postsynaptic actin filament assembly. Differences in the two LPP termination sites were also noted for frequency facilitation of synaptic responses, an effect that was reproduced in a two-step simulation by small adjustments to vesicle release dynamics. These results indicate that different types of glutamatergic neurons impose different forms of filtering and synaptic plasticity on their afferents. They also suggest that inputs are routed to, and encoded by, different sites within the hippocampus depending upon the pattern of activity arriving over the parent axon.


Assuntos
Giro Denteado , Potenciação de Longa Duração , Masculino , Camundongos , Animais , Potenciação de Longa Duração/fisiologia , Giro Denteado/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Hipocampo/metabolismo , Plasticidade Neuronal/fisiologia , Estimulação Elétrica/métodos
3.
Neurologia (Engl Ed) ; 2023 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-37116689

RESUMO

BACKGROUND: In addition to stent retrievers, direct aspiration has become a reasonable thrombectomy strategy. OBJECTIVES: We carried out the thrombectomy by guiding the aspiration catheter fully over the clot and performing immediate manual aspiration; we call this procedure "embed aspiration". METHODS: In this prospective, non-randomised, single-centre study, we included all patients treated at a high volume-of-care stroke centre between 2017 and 2018 for the TRIANA (Thrombectomy in Andalusia using Aspiration) registry. Thrombectomy was carried out by embed aspiration. Patients were classified according to the success (eTICI 2b67-2c-3) or failure (eTICI 0-1-2a-2b50) of the procedure. Baseline clinical data and outcomes were compared, and multivariate analysis was performed. RESULTS: The embed aspiration technique was used in 370 patients. Treatment was successful in 90.3% of patients. Mean puncture-to-recanalisation time was 25 minutes. The overall rate of good outcomes (mRS 0-2) at 3 months was 64%. CONCLUSIONS: This study supports real-life evidence that standardised embed aspiration may be an alternative to stent retrievers for thrombectomy.

4.
Front Physiol ; 13: 837661, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36225294

RESUMO

Exposure to adverse childhood experiences or early life stress experiences (ELSs) increase the risk of non-adaptive behaviors and psychopathology in adulthood. Environmental enrichment (EE) has been proposed to minimize these effects. The vast number of methodological variations in animal studies underscores the lack of systematicity in the studies and the need for a detailed understanding of how enrichment interacts with other variables. Here we evaluate the effects of environmental enrichment in male and female Wistar rats exposed to adverse early life experiences (prenatal, postnatal, and combined) on emotional (elevated plus maze), social (social interaction chamber), memory (Morris water maze) and flexibility tasks. Our results-collected from PND 51 to 64-confirmed: 1) the positive effect of environmental enrichment (PND 28-49) on anxiety-like behaviors in animals submitted to ELSs. These effects depended on type of experience and type of enrichment: foraging enrichment reduced anxiety-like behaviors in animals with prenatal and postnatal stress but increased them in animals without ELSs. This effect was sex-dependent: females showed lower anxiety compared to males. Our data also indicated that females exposed to prenatal and postnatal stress had lower anxious responses than males in the same conditions; 2) no differences were found for social interactions; 3) concerning memory, there was a significant interaction between the three factors: A significant interaction for males with prenatal stress was observed for foraging enrichment, while physical enrichment was positive for males with postnatal stress; d) regarding cognitive flexibility, a positive effect of EE was found in animals exposed to adverse ELSs: animals with combined stress and exposed to physical enrichment showed a higher index of cognitive flexibility than those not exposed to enrichment. Yet, within animals with no EE, those exposed to combined stress showed lower flexibility than those exposed to both prenatal stress and no stress. On the other hand, animals with prenatal stress and exposed to foraging-type enrichment showed lower cognitive flexibility than those with no EE. The prenatal stress-inducing conditions used here 5) did not induced fetal or maternal problems and 6) did not induced changes in the volume of the dentate gyrus of the hippocampus.

5.
Radiologia (Engl Ed) ; 64(2): 169-178, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35504683

RESUMO

Mónico Sánchez Moreno (1880-1961) was an important figure in the early years of electromedicine, rubbing elbows with world-class physicists like Nikola Tesla. Her main contribution to the field was the invention and commercialization of a portable X-ray generator, replacing the heavy transformer had been necessary to generate power with a lightweight portable device that could work with direct or alternating current at 220 or 125V. This device was easily adaptable to other applications in electromedicine, such as cauterization or disinfection. This indefatigable entrepreneur could have triumphed in America, but preferred to work toward furthering technological development in the land that she loved. Her efforts made it possible to have an affordable device made in Spain that would allow radiological examinations to be done in places where it would have been otherwise unthinkable. In conclusion, Mónico Sánchez Moreno was a self-made woman who deserves to be remembered for her pioneering role in portable radiology.


Assuntos
Radiologia , Tecnologia Radiológica , Feminino , Humanos , Espanha
6.
Radiología (Madr., Ed. impr.) ; 64(2): 169-178, Mar-Abr 2022. ilus
Artigo em Espanhol | IBECS | ID: ibc-204422

RESUMO

Mónico Sánchez Moreno (1880-1961) fue un personaje destacado en los primeros años de la electromedicina, llegando a codearse con figuras encumbradas de la física mundial como Nikola Tesla. Su principal aportación fue la invención y comercialización de un generador portátil de rayos X, sustituyendo el pesado transformador que se requería para generar corriente por un equipo ligero, portátil, que funcionaba con corriente continua o alterna, a 220 o 125 V, fácilmente adaptable para otras aplicaciones de electromedicina como la cauterización o la desinfección. Este emprendedor infatigable, que podía haber triunfado en América, prefirió invertir su esfuerzo en impulsar el desarrollo tecnológico en la tierra que amaba, permitiendo disponer de un equipo de fabricación nacional, asequible, que pudo llevar la exploración radiológica a rincones impensables de otro modo. En conclusión, Mónico Sánchez Moreno fue un hombre hecho a sí mismo, que merece ser recordado como pionero de la radiología portátil.(AU)


Mónico Sánchez Moreno (1880-1961) was an important figure in the early years of electromedicine, rubbing elbows with world-class physicists like Nikola Tesla. Her main contribution to the field was the invention and commercialization of a portable X-ray generator, replacing the heavy transformer had been necessary to generate power with a lightweight portable device that could work with direct or alternating current at 220 or 125V. This device was easily adaptable to other applications in electromedicine, such as cauterization or disinfection. This indefatigable entrepreneur could have triumphed in America, but preferred to work toward furthering technological development in the land that she loved. Her efforts made it possible to have an affordable device made in Spain that would allow radiological examinations to be done in places where it would have been otherwise unthinkable. In conclusion, Mónico Sánchez Moreno was a self-made woman who deserves to be remembered for her pioneering role in portable radiology.(AU)


Assuntos
Humanos , Masculino , Tecnologia Radiológica , Raios X , Radiologia , Radiologistas , Radiografia , Fluoroscopia , História , Espanha , Equipamentos de Laboratório
7.
Radiologia (Engl Ed) ; 2021 Jul 28.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-34332785

RESUMO

Mónico Sánchez Moreno (1880-1961) was an important figure in the early years of electromedicine, rubbing elbows with world-class physicists like Nikola Tesla. Her main contribution to the field was the invention and commercialization of a portable X-ray generator, replacing the heavy transformer had been necessary to generate power with a lightweight portable device that could work with direct or alternating current at 220 or 125V. This device was easily adaptable to other applications in electromedicine, such as cauterization or disinfection. This indefatigable entrepreneur could have triumphed in America, but preferred to work toward furthering technological development in the land that she loved. Her efforts made it possible to have an affordable device made in Spain that would allow radiological examinations to be done in places where it would have been otherwise unthinkable. In conclusion, Mónico Sánchez Moreno was a self-made woman who deserves to be remembered for her pioneering role in portable radiology.

8.
Med Oral Patol Oral Cir Bucal ; 26(6): e762-e769, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34023839

RESUMO

BACKGROUND: The objective of this study was to analyse the association between oral and general health variables and obesity indicators with the sensation of dry mouth or xerostomia as evaluated on the Xerostomia Inventory (XI). MATERIAL AND METHODS: A total of 354 randomly selected subjects participated in this cross-sectional pilot study and completed an anonymous questionnaire. Anthropometric, clinical, and xerostomic variables were evaluated. Kruskal-Wallis, ANOVA and Bonferroni test were used for multiple comparisons. ROC curves and multinomial logistic regression were used to determine the (OR) risk of xerostomia. RESULTS: A total of 30.7 % of respondents reported xerostomia based on XI. The dry mouth question, the XI taken as a "gold standard", showed a diagnostic sensitivity of 70.37 %, and a specificity of 83.27 % (AUC=0.768, p<0.001). Logistical regression showed the highest xerostomia OR was associated to patients with bad self-perceived health, 6.31 (CI 95% 2.89-13.80, p<0.001). In the model adjusted for tooth mobility, bone or respiratory diseases, and the consumption of anxiolytics and antidepressants, the OR was 3.46 (CI 95% 1.47-8.18, p=0.005). CONCLUSIONS: a high prevalence of xerostomia was found in this cross-sectional pilot study, which was significantly more frequent in women, and increased with age. Xerostomia was associated to several systemic diseases, psychological conditions, and oral functional disorders such as tooth mobility. These preliminary results can serve as the basis for developing guidelines for the application of innovative measures designed to improve the quality of life of individuals with xerostomia.


Assuntos
Qualidade de Vida , Xerostomia , Adulto , Estudos Transversais , Feminino , Humanos , Masculino , Obesidade/complicações , Obesidade/epidemiologia , Projetos Piloto , Inquéritos e Questionários , Xerostomia/epidemiologia , Xerostomia/etiologia
9.
J Phys Condens Matter ; 33(19)2021 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-33545697

RESUMO

In recent years, artificial intelligence techniques have proved to be very successful when applied to problems in physical sciences. Here we apply an unsupervised machine learning (ML) algorithm called principal component analysis (PCA) as a tool to analyse the data from muon spectroscopy experiments. Specifically, we apply the ML technique to detect phase transitions in various materials. The measured quantity in muon spectroscopy is an asymmetry function, which may hold information about the distribution of the intrinsic magnetic field in combination with the dynamics of the sample. Sharp changes of shape of asymmetry functions-measured at different temperatures-might indicate a phase transition. Existing methods of processing the muon spectroscopy data are based on regression analysis, but choosing the right fitting function requires knowledge about the underlying physics of the probed material. Conversely, PCA focuses on small differences in the asymmetry curves and works without any prior assumptions about the studied samples. We discovered that the PCA method works well in detecting phase transitions in muon spectroscopy experiments and can serve as an alternative to current analysis, especially if the physics of the studied material are not entirely known. Additionally, we found out that our ML technique seems to work best with large numbers of measurements, regardless of whether the algorithm takes data only for a single material or whether the analysis is performed simultaneously for many materials with different physical properties.

11.
Ann Anat ; 232: 151582, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32810612

RESUMO

BACKGROUND: The Chievitz's organ or juxta-oral organ is a mysterious bilateral structure, phylogenetically preserved, which develops from the mouth epithelium as an invagination that loses connection to it in the prenatal period. It is located laterally to the walls of the oral cavity in an imprecise anatomical location and receives abundant innervation from the buccal nerve. Structurally it consists of non-keratinizing squamous-like neuroepithelial cells surrounded by two layers of connective tissue with nerve fibers and different morphotypes of sensory corpuscles. Its function is completely unknown although based on its rich innervation it is assumed that works as a mechanoreceptor. METHODS: We have performed immunohistochemistry for axonal and Schwann cells, and the putative mechanoproteins ASIC2, TRPV4 and Piezo2 in sections of fetal juxta-oral organ. RESULTS: Intraparenchymatous nerve fibers and sensory corpuscles were observed as well as immunoreactivity for Piezo2 in both nerve fibers and epithelial parenchymatous cells. CONCLUSIONS: We add indirect evidence that the juxtaoral organ is a mechanoreceptor because in addition to its dense innervation, the epithelial cells and sensory nerve fibers display immunoreactivity for the mechanogated ion channel Piezo2. Based on current knowledge, the functional and clinical importance of the juxta-oral organ should be further investigated.


Assuntos
Bochecha/anatomia & histologia , Bochecha/embriologia , Bochecha/patologia , Bochecha/fisiologia , Feto/anatomia & histologia , Humanos , Imuno-Histoquímica , Canais Iônicos de Abertura Ativada por Ligante/fisiologia , Tecido Parenquimatoso/anatomia & histologia , Tecido Parenquimatoso/inervação
12.
Med. oral patol. oral cir. bucal (Internet) ; 25(3): e318-e325, mayo 2020.
Artigo em Inglês | IBECS | ID: ibc-196317

RESUMO

BACKGROUND: The relation between periodontal disease and systemic pathologies is still not widespread among general practitioners. The aim of our study is to evaluate whether or not periodontal radiological diagnosis can aid the detection of blood alterations associated with acquired systemic diseases. MATERIAL AND METHODS: This is a cross sectional study. All of the participants underwent a panoramic radiograph and a complete blood test. Morphological bone loss was considered as positive in those patients who showed radiographically more than 1 tooth with bone loss greater than or equal to the middle third of the root. The statistical analysis was performed by comparing the variables using the ANOVA or U-Mann-Whitney tests for independent samples with normal conditions. The correlation coefficient was analysed using the Pearson test. RESULTS: 239 patients were included in our study (96 men and 143 women) with an average age of 64.40 years. 59.04% of the patients were determined as morphological bone loss positive and had on average 4 teeth less than negative patients (p < 0.0001). Also the average platelet levels in positive patients were lower (p = 0.024) and mean levels of HBA1c (p = 0.009) were higher. CONCLUSIONS: Morphological bone loss parameter can be useful both for dentists and general practitioners to refer, subsequently, to periodontal specialist


No disponible


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Perda do Osso Alveolar/sangue , Hemoglobinas Glicadas/análise , Perda do Osso Alveolar/diagnóstico por imagem , Estudos Transversais , Contagem de Plaquetas , Análise de Variância , Estatísticas não Paramétricas , Análise Química do Sangue , Valores de Referência , Perda do Osso Alveolar/fisiopatologia
13.
Med Oral Patol Oral Cir Bucal ; 25(3): e318-e325, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32134896

RESUMO

BACKGROUND: The relation between periodontal disease and systemic pathologies is still not widespread among general practitioners. The aim of our study is to evaluate whether or not periodontal radiological diagnosis can aid the detection of blood alterations associated with acquired systemic diseases. MATERIAL AND METHODS: This is a cross sectional study. All of the participants underwent a panoramic radiograph and a complete blood test. Morphological bone loss was considered as positive in those patients who showed radiographically more than 1 tooth with bone loss greater than or equal to the middle third of the root. The statistical analysis was performed by comparing the variables using the ANOVA or U-Mann-Whitney tests for independent samples with normal conditions. The correlation coefficient was analysed using the Pearson test. RESULTS: 239 patients were included in our study (96 men and 143 women) with an average age of 64.40 years. 59.04% of the patients were determined as morphological bone loss positive and had on average 4 teeth less than negative patients (p <0.0001). Also the average platelet levels in positive patients were lower (p = 0.024) and mean levels of HBA1c (p = 0.009) were higher. CONCLUSIONS: Morphological bone loss parameter can be useful both for dentists and general practitioners to refer, subsequently, to periodontal specialist.


Assuntos
Perda do Osso Alveolar , Processo Alveolar , Estudos Transversais , Feminino , Hemoglobinas Glicadas , Testes Hematológicos , Humanos , Masculino , Pessoa de Meia-Idade
15.
Ann Anat ; 219: 8-24, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29842990

RESUMO

Meissner's and Pacinian corpuscles are cutaneous mechanoreceptors responsible for different modalities of touch. The development of these sensory formations in humans is poorly known, especially regarding the acquisition of the typical immunohistochemical profile related to their full functional maturity. Here we used a panel of antibodies (to specifically label the main corpuscular components: axon, Schwann-related cells and endoneurial-perineurial-related cells) to investigate the development of digital Meissner's and Pacinian corpuscles in a representative sample covering from 11 weeks of estimated gestational age (wega) to adulthood. Development of Pacinian corpuscles starts at 13 wega, and it is completed at 4 months of life, although their basic structure and immunohistochemical characteristics are reached at 36 wega. During development, around the axon, a complex network of S100 positive Schwann-related processes is progressively compacted to form the inner core, while the surrounding mesenchyme is organized and forms the outer core and the capsule. Meissner's corpuscles start to develop at 22 wega and complete their typical morphology and immunohistochemical profile at 8 months of life. In developing Meissner's corpuscles, the axons establish complex relationships with the epidermis and are progressively covered by Schwann-like cells until they complete the mature arrangement late in postnatal life. The present results demonstrate an asynchronous development of the Meissner's and Pacini's corpuscles and show that there is not a total correlation between morphological and immunohistochemical maturation. The correlation of the present results with touch-induced cortical activity in developing humans is discussed.


Assuntos
Dedos/anatomia & histologia , Mecanorreceptores/fisiologia , Corpúsculos de Pacini/crescimento & desenvolvimento , Adolescente , Adulto , Idoso , Animais , Anticorpos/imunologia , Axônios/fisiologia , Colágeno Tipo IV/análise , Feminino , Dedos/embriologia , Imunofluorescência , Idade Gestacional , Humanos , Imuno-Histoquímica , Lactente , Recém-Nascido , Masculino , Mecanorreceptores/citologia , Camundongos , Pessoa de Meia-Idade , Corpúsculos de Pacini/embriologia , Gravidez , Coelhos , Pele/anatomia & histologia , Pele/embriologia , Pele/crescimento & desenvolvimento
16.
Phys Rev Lett ; 121(25): 257002, 2018 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-30608781

RESUMO

To trace the origin of time-reversal symmetry breaking (TRSB) in Re-based superconductors, we performed comparative muon-spin rotation and relaxation (µSR) studies of superconducting noncentrosymmetric Re_{0.82}Nb_{0.18} (T_{c}=8.8 K) and centrosymmetric Re (T_{c}=2.7 K). In Re_{0.82}Nb_{0.18}, the low-temperature superfluid density and the electronic specific heat evidence a fully gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling. In both Re_{0.82}Nb_{0.18} and pure Re, the spontaneous magnetic fields revealed by zero-field µSR below T_{c} indicate time-reversal symmetry breaking and thus unconventional superconductivity. The concomitant occurrence of TRSB in centrosymmetric Re and noncentrosymmetric ReT (T=transition metal), yet its preservation in the isostructural noncentrosymmetric superconductors Mg_{10}Ir_{19}B_{16} and Nb_{0.5}Os_{0.5}, strongly suggests that the local electronic structure of Re is crucial for understanding the TRSB superconducting state in Re and ReT. We discuss the superconducting order parameter symmetries that are compatible with the experimental observations.

17.
Semergen ; 44(2): 138-143, 2018 Mar.
Artigo em Espanhol | MEDLINE | ID: mdl-28552687

RESUMO

An association has been found between oral health problems and obstetric complications during pregnancy. The main aim of this study was to assess the perception by pregnant women on their oral health and related habits and beliefs. A questionnaire was designed in order to obtain information from 96 pregnant women attending the Valdeorras Local Hospital and the primary health dental practice in the Valle Inclan Health Center. It was found that many pregnant women perceived they were suffering from some kind of problem affecting their mouth. It was shown that pregnant women had adequate habits regarding oral health, but they believed that their pregnancy would implicitly cause them to have mouth problems. Pregnant women are able to understand the impact of their oral health on their general well-being and the health of their unborn child. It has been detected that a series of habits and beliefs would ideally need to be acted upon in order to reduce health problems.


Assuntos
Doenças da Boca/epidemiologia , Saúde Bucal , Higiene Bucal , Complicações na Gravidez/epidemiologia , Adulto , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Pessoa de Meia-Idade , Doenças da Boca/complicações , Gravidez , Complicações na Gravidez/etiologia , Autoavaliação (Psicologia) , Espanha/epidemiologia , Inquéritos e Questionários , Adulto Jovem
18.
Surg Radiol Anat ; 39(7): 717-723, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27933368

RESUMO

PURPOSE: To analyze anatomical variations of the greater palatine canal (GPC) using cone beam computed tomography (CBCT) images. METHODS: This study included 110 CBCTs. Axial slices were used to determine the shape of GPC and the number of lesser palatine foramina (LPF). Sagittal slices were used to assess the shape of the GPC and the number of lesser palatine canals (LPCs). RESULTS: The most prevalent axial and sagittal GPC shapes were oval (46.36%) and hourglass (23.64%). Most GPCs presented one LPF (47.27%) and one LPC (90.91%). CONCLUSIONS: GPC anatomy is highly variable. CBCT is a useful tool for evaluating the anatomical variations of GPC.


Assuntos
Boca/anatomia & histologia , Fossa Pterigopalatina/anatomia & histologia , Variação Anatômica , Tomografia Computadorizada de Feixe Cônico , Feminino , Humanos , Masculino , Boca/diagnóstico por imagem , Fossa Pterigopalatina/diagnóstico por imagem
19.
Phys Rev Lett ; 117(2): 027001, 2016 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-27447519

RESUMO

The nature of the pairing states of superconducting LaNiC_{2} and LaNiGa_{2} has to date remained a puzzling question. Broken time reversal symmetry has been observed in both compounds and a group theoretical analysis implies a nonunitary triplet pairing state. However, all the allowed nonunitary triplet states have nodal gap functions but most thermodynamic and NMR measurements indicate fully gapped superconductivity in LaNiC_{2}. Here we probe the gap symmetry of LaNiGa_{2} by measuring the London penetration depth, specific heat, and upper critical field. These measurements demonstrate two-gap nodeless superconductivity in LaNiGa_{2}, suggesting that this is a common feature of both compounds. These results allow us to propose a novel triplet superconducting state, where the pairing occurs between electrons of the same spin, but on different orbitals. In this case the superconducting wave function has a triplet spin component but isotropic even parity gap symmetry, yet the overall wave function remains antisymmetric under particle exchange. This model leads to a nodeless two-gap superconducting state which breaks time reversal symmetry, and therefore accounts well for the seemingly contradictory experimental results.

20.
Environ Sci Pollut Res Int ; 23(7): 6919-33, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26676541

RESUMO

Methylation and demethylation represent major transformation pathways regulating the net production of methylmercury (MMHg). Very few studies have documented Hg reactivity and transformation in extreme high-altitude lake ecosystems. Mercury (Hg) species concentrations (IHg, MMHg, Hg°, and DMHg) and in situ Hg methylation (M) and MMHg demethylation (D) potentials were determined in water, sediment, floating organic aggregates, and periphyton compartments of a shallow productive Lake of the Bolivian Altiplano (Uru Uru Lake, 3686 m). Samples were collected during late dry season (October 2010) and late wet season (May 2011) at a north (NS) and a south (SS) site of the lake, respectively. Mercury species concentrations exhibited significant diurnal variability as influenced by the strong diurnal biogeochemical gradients. Particularly high methylated mercury concentrations (0.2 to 4.5 ng L(-1) for MMHgT) were determined in the water column evidencing important Hg methylation in this ecosystem. Methylation and D potentials range were, respectively, <0.1-16.5 and <0.2-68.3 % day(-1) and were highly variable among compartments of the lake, but always higher during the dry season. Net Hg M indicates that the influence of urban and mining effluent (NS) promotes MMHg production in both water (up to 0.45 ng MMHg L(-1) day(-1)) and sediment compartments (2.0 to 19.7 ng MMHg g(-1) day(-1)). While the sediment compartment appears to represent a major source of MMHg in this shallow ecosystem, floating organic aggregates (dry season, SS) and Totora's periphyton (wet season, NS) were found to act as a significant source (5.8 ng MMHg g(-1) day(-1)) and a sink (-2.1 ng MMHg g(-1) day(-1)) of MMHg, respectively. This work demonstrates that high-altitude productive lake ecosystems can promote MMHg formation in various compartments supporting recent observations of high Hg contents in fish and water birds.


Assuntos
Monitoramento Ambiental , Lagos/química , Mercúrio/análise , Poluentes Químicos da Água/análise , Altitude , Animais , Bolívia , Ecossistema , Meio Ambiente , Peixes/metabolismo , Compostos de Metilmercúrio/química , Mineração , Estações do Ano
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...