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1.
Eur J Pain ; 2024 Feb 08.
Artículo en Inglés | MEDLINE | ID: mdl-38329141

RESUMEN

BACKGROUND: The relatively stable individual differences reflected in Grey's revised reinforcement sensitivity theory (rRST), with foundations in neurophysiology and learning theory, appear particularly applicable to the study of pain. However, remarkably little research has been conducted in this area. In acute pain, activation of the behavioural approach system (BAS), the behavioural inhibition system (BIS) and the fight, flight, freezing system might depend on an individual's evaluation of pain. It was thus hypothesised that higher-order interactions of rRST traits and pain attitudes affect pain responsiveness. METHODS: To investigate relationships between rRST traits and pain attitudes and to identify patterns between clusters of participants, we conducted a study in which N = 275 healthy participants filled in Reuter and Montag's rRST-Q and the General Attitudes Towards Pain Inventory (GATPI). Experimental (pressure, electrical, thermal) and self-report data of pain responsiveness were collected in a subsample (N = 113). RESULTS: We found significant correlations between rRST-Q and GATPI subscales of up to r = 0.34. Two clusters were identified, significantly differing in rRST-Q and GATPI scores. Pain avoiders, characterized by high BIS, flight, freezing and negative pain attitudes, were found to be significantly more pain sensitive than pain approachers, characterized by high BAS, fight and positive pain attitudes. Moderate effects (d = 0.56 to d = 0.70) were demonstrated in subjective and objective measures and across pain modalities. CONCLUSIONS: The present study expands the scientific knowledge on factors influencing pain responsiveness. Future research is needed to confirm implications for chronic pain prevention and therapy, particularly concerning pain avoiders. SIGNIFICANCE: We have identified two clusters of participants, pain avoiders and pain approachers, that not only present differential patterns of revised reinforcement theory traits and general attitudes towards pain but also differ in their pain responsiveness. Pain avoiders appeared more pain sensitive compared to pain approachers, both in objective and subjective measurements, with implications for the improvement of chronic pain prevention and therapy.

2.
BMC Genom Data ; 24(1): 26, 2023 05 02.
Artículo en Inglés | MEDLINE | ID: mdl-37131148

RESUMEN

HostSeq was launched in April 2020 as a national initiative to integrate whole genome sequencing data from 10,000 Canadians infected with SARS-CoV-2 with clinical information related to their disease experience. The mandate of HostSeq is to support the Canadian and international research communities in their efforts to understand the risk factors for disease and associated health outcomes and support the development of interventions such as vaccines and therapeutics. HostSeq is a collaboration among 13 independent epidemiological studies of SARS-CoV-2 across five provinces in Canada. Aggregated data collected by HostSeq are made available to the public through two data portals: a phenotype portal showing summaries of major variables and their distributions, and a variant search portal enabling queries in a genomic region. Individual-level data is available to the global research community for health research through a Data Access Agreement and Data Access Compliance Office approval. Here we provide an overview of the collective project design along with summary level information for HostSeq. We highlight several statistical considerations for researchers using the HostSeq platform regarding data aggregation, sampling mechanism, covariate adjustment, and X chromosome analysis. In addition to serving as a rich data source, the diversity of study designs, sample sizes, and research objectives among the participating studies provides unique opportunities for the research community.


Asunto(s)
COVID-19 , SARS-CoV-2 , Humanos , SARS-CoV-2/genética , COVID-19/epidemiología , Canadá/epidemiología , Genómica , Secuenciación Completa del Genoma
3.
Sci Rep ; 11(1): 21637, 2021 11 04.
Artículo en Inglés | MEDLINE | ID: mdl-34737364

RESUMEN

Understanding of emotions and intentions are key processes in social cognition at which serotonin is an important neuromodulator. Its precursor is the essential amino acid tryptophan (TRP). Reduced TRP availability leads to weaker impulse control ability and higher aggression, while TRP supplementation promotes confidence. In a double-blind placebo-controlled fMRI study with 77 healthy adults, we investigated the influence of a 4 week TRP enriched diet and an acute 5-hydroxytryptophan (5-HTP) intake on two social-cognitive tasks, a moral evaluation and an emotion recognition task. With 5-HTP, immoral behavior without negative consequences was rated as more reprehensible. Additionally, during story reading, activation in insula and supramarginal gyrus was increased after TRP intake. No significant effects of TRP on emotion recognition were identified for the whole sample. Importantly, emotion recognition ability decreased with age which was for positive emotions compensated by TRP. Since the supramarginal gyrus is associated with empathy, pain and related information integration results could be interpreted as reflecting stricter evaluation of negative behavior due to better integration of information. Improved recognition of positive emotions with TRP in older participants supports the use of a TRP-rich diet to compensate for age related decline in social-cognitive processes.


Asunto(s)
Emociones/efectos de los fármacos , Cognición Social , Triptófano/farmacología , 5-Hidroxitriptófano/metabolismo , 5-Hidroxitriptófano/farmacología , Adulto , Afecto/efectos de los fármacos , Cognición/efectos de los fármacos , Suplementos Dietéticos , Método Doble Ciego , Femenino , Voluntarios Sanos , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Neurotransmisores/metabolismo , Neurotransmisores/farmacología , Placebos , Reconocimiento en Psicología/efectos de los fármacos , Serotonina/metabolismo , Triptófano/metabolismo
4.
Food Funct ; 11(9): 8320-8330, 2020 Sep 23.
Artículo en Inglés | MEDLINE | ID: mdl-32910112

RESUMEN

Recently, a relationship has been observed between nutrition and social cognition. In this aspect, several dietary patterns, or even some probiotics, have been reported as social cognition modulators. However, to date, no studies have reported the effects of specific nutrients. Our aim was to evaluate the relationship between dietary macronutrients and the processing of social and affective information. Participants were undergraduates from the University of Extremadura (Badajoz, Spain) aged 21.3 ± 2.9 years., with a BMI of 22.8 ± 3.9 (kg m-2). The students' social cognition and diet were analysed through questionnaires and a dietary record. The diets were analysed with DIAL v.1.18® software (Alce Ingeniería®). The participants filled out the WHO-5 well-being index, Beck's anxiety inventory, Beck's depression inventory, ruminative response scale (RSS), Leiden index of depression sensitivity (LEIDS-r), empathy quotient (EQ), and interpersonal reactivity index (IRI). To analyse the data, nutrients were grouped through principal component analysis (PCA) into lipids, carbohydrates and proteins. Additionally, we assayed if these principal components were associated with psychological questionnaire scores using multiple linear regression analyses. The dietary pattern differed from the traditional Mediterranean diet due to high intake of proteins and saturated fatty acids. Regarding social cognition and macronutrients, we found a positive association between lipids, specifically cholesterol, and the Perspective-Taking Scale (an IRI component). Carbohydrates influenced the RSS, indicating that complex carbohydrates may be a risk factor for depression. Moreover, the brooding factor, a component of the RRS, was negatively affected by dietary carbohydrates and proteins, specifically by fiber and aspartate. Diet may influence several variables related to social cognition and mood. Particularly, a low-cholesterol diet rich in fiber, complex carbohydrates, and aspartate apparently provides benefits, improving the processing of social and affective information and psychic well-being.


Asunto(s)
Afecto , Dieta/psicología , Cognición Social , Adulto , Femenino , Humanos , Masculino , Proyectos Piloto , España , Adulto Joven
5.
Biol Lett ; 16(2): 20190891, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-32097597

RESUMEN

Organismal fitness is partly determined by how well the nutritional intake matches sex-specific metabolic requirements. Metabolism itself is underpinned by complex genomic interactions involving products from both nuclear and mitochondrial genomes. Products from these two genomes must coordinate how nutrients are extracted, used and recycled, processes vital for fuelling reproduction. Given the complicated nature of metabolism, it is not well understood how the functioning of these two genomes is modulated by nutrients. Here we use nutritional geometry techniques on Drosophila lines that only differ in their mtDNA, with the aim to understand if there is nutrient-dependent mitochondrial genetic variance for male reproduction. We first find genetic variance for diet consumption, indicating that flies are consuming different amounts of food to meet new physiological requirements. We then find an interaction between mtDNA and diet for fitness, suggesting that the mtDNA plays a role in modulating diet-dependent fitness. Our results enhance our basic understanding of nutritional health and our chimeric genomes.


Asunto(s)
ADN Mitocondrial , Genoma Mitocondrial , Animales , Núcleo Celular , Femenino , Fertilidad , Masculino , Mitocondrias/genética
6.
Urologe A ; 58(9): 1029-1038, 2019 Sep.
Artículo en Alemán | MEDLINE | ID: mdl-31451881

RESUMEN

The demographic developments of western society and the resulting increase in the number of very old patients in urology represents a challenge for the design of clinical studies and, consequently, recommendations of guidelines. While in internal medicine there is already a subspecialization with a focus on the treatment of elderly and multimorbid patients, in urology there is hardly any subspecialization into the problems of geriatric patients. Thus, using a case study as an example, the treatment decisions for benign prostatic hyperplasia (BPH) in geriatric patients are discussed. In addition the available evidence from the literature and guidelines are presented in order to assiste in daily management of geriatric patients with lower urinary tract symptoms and to critically discuss potential fields of application and limitations of the existing guidelines. In this context, we also examine the challenges when choosing a drug therapy and in deciding which of the many surgical options should be used.


Asunto(s)
Síntomas del Sistema Urinario Inferior/diagnóstico , Síntomas del Sistema Urinario Inferior/terapia , Guías de Práctica Clínica como Asunto , Hiperplasia Prostática/diagnóstico , Hiperplasia Prostática/terapia , Urología/normas , Anciano , Humanos , Síntomas del Sistema Urinario Inferior/etiología , Masculino , Hiperplasia Prostática/etiología
7.
J Environ Manage ; 234: 546-553, 2019 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-30708311

RESUMEN

As the mining industry is facing an increasing number of issues related to its fresh water consumption, water-saving strategies are progressively being implemented in the mineral processing plants, often leading to variations in the process water chemistry. However, the impact of water chemistry variations on the process performance is rarely known beforehand, thus creating an obstacle to the implementation of those water-saving strategies. To tackle this problem, the effect the different dissolved species present in the process water have on the processing plant performance must be quantified, and this information must be digitalized in a practical and suitable form to be used in mineral processing simulators. To achieve this goal, a methodology to digitalize the influence of the process water composition on the flotation performance is presented in this paper. Using the flotation of a fluorite ore as case study, the relationship between process water composition and the flotation kinetics of that fluorite ore was determined. This relationship was digitalized in HSC Sim, a mineral processing simulator, turning it into a tool capable of simulating the flotation performance under a variety of process water compositions. Finally, the potential of this new tool to help implementing water-saving strategies on the mine site is discussed, and the challenges that need to be overcome in order to apply this tool at industrial scale are being addressed.


Asunto(s)
Contaminantes Químicos del Agua , Agua , Cinética , Minerales
8.
Neuroimage ; 155: 370-382, 2017 07 15.
Artículo en Inglés | MEDLINE | ID: mdl-28479476

RESUMEN

The amygdala is composed of multiple nuclei with unique functions and connections in the limbic system and to the rest of the brain. However, standard in vivo neuroimaging tools to automatically delineate the amygdala into its multiple nuclei are still rare. By scanning postmortem specimens at high resolution (100-150µm) at 7T field strength (n = 10), we were able to visualize and label nine amygdala nuclei (anterior amygdaloid, cortico-amygdaloid transition area; basal, lateral, accessory basal, central, cortical medial, paralaminar nuclei). We created an atlas from these labels using a recently developed atlas building algorithm based on Bayesian inference. This atlas, which will be released as part of FreeSurfer, can be used to automatically segment nine amygdala nuclei from a standard resolution structural MR image. We applied this atlas to two publicly available datasets (ADNI and ABIDE) with standard resolution T1 data, used individual volumetric data of the amygdala nuclei as the measure and found that our atlas i) discriminates between Alzheimer's disease participants and age-matched control participants with 84% accuracy (AUC=0.915), and ii) discriminates between individuals with autism and age-, sex- and IQ-matched neurotypically developed control participants with 59.5% accuracy (AUC=0.59). For both datasets, the new ex vivo atlas significantly outperformed (all p < .05) estimations of the whole amygdala derived from the segmentation in FreeSurfer 5.1 (ADNI: 75%, ABIDE: 54% accuracy), as well as classification based on whole amygdala volume (using the sum of all amygdala nuclei volumes; ADNI: 81%, ABIDE: 55% accuracy). This new atlas and the segmentation tools that utilize it will provide neuroimaging researchers with the ability to explore the function and connectivity of the human amygdala nuclei with unprecedented detail in healthy adults as well as those with neurodevelopmental and neurodegenerative disorders.


Asunto(s)
Amígdala del Cerebelo/anatomía & histología , Amígdala del Cerebelo/diagnóstico por imagen , Atlas como Asunto , Procesamiento de Imagen Asistido por Computador/métodos , Imagen por Resonancia Magnética/métodos , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/diagnóstico por imagen , Amígdala del Cerebelo/patología , Trastorno del Espectro Autista/diagnóstico por imagen , Femenino , Humanos , Masculino , Persona de Mediana Edad
9.
Ophthalmologe ; 113(8): 684-9, 2016 Aug.
Artículo en Alemán | MEDLINE | ID: mdl-27048550

RESUMEN

BACKGROUND: On the initiative of professionals performing vision screening for primary school enrolment, we compared the laptop-based Freiburg acuity and contrast test (FrACT) as a more easily portable alternative to the traditionally employed tumbling E vision test. METHODS: We assessed vision with both methods in 326 children (647 eyes) aged 3.8-6.9 years. The FrACT was set to present the Landolt C optotype with the four cardinal orientations and automatic threshold bracketing over 18 presentations. RESULTS: The 95% limits of agreement between both methods were ±0.125 logMAR and 95% of all test differences were within slightly more than ±1 line. Over the examined age range acuity significantly but weakly increased (p < 0.01) from 0.7 to 0.9 and for Landolt Cs the acuity gain was slightly higher by 0.02 logMAR per year. The FrACT results were ≥3 lines lower than those of the tumbling E chart in only 6 eyes. The examiners unanimously preferred FrACT. DISCUSSION: The agreement between both tests of approximately ±1 lines is very high. The low outlier rate of <1% is deemed to be acceptable for a screening test.


Asunto(s)
Guías de Práctica Clínica como Asunto , Estudiantes , Selección Visual/métodos , Pruebas de Visión/métodos , Pruebas de Visión/normas , Agudeza Visual , Niño , Preescolar , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Selección Visual/normas
10.
Genes Brain Behav ; 15(5): 453-64, 2016 06.
Artículo en Inglés | MEDLINE | ID: mdl-27079569

RESUMEN

Face cognition, including face identity and facial expression processing, is a crucial component of socio-emotional abilities, characterizing humans as highest developed social beings. However, for these trait domains molecular genetic studies investigating gene-behavior associations based on well-founded phenotype definitions are still rare. We examined the relationship between 5-HTTLPR/rs25531 polymorphisms - related to serotonin-reuptake - and the ability to perceive and recognize faces and emotional expressions in human faces. For this aim we conducted structural equation modeling on data from 230 young adults, obtained by using a comprehensive, multivariate task battery with maximal effort tasks. By additionally modeling fluid intelligence and immediate and delayed memory factors, we aimed to address the discriminant relationships of the 5-HTTLPR/rs25531 polymorphisms with socio-emotional abilities. We found a robust association between the 5-HTTLPR/rs25531 polymorphism and facial emotion perception. Carriers of two long (L) alleles outperformed carriers of one or two S alleles. Weaker associations were present for face identity perception and memory for emotional facial expressions. There was no association between the 5-HTTLPR/rs25531 polymorphism and non-social abilities, demonstrating discriminant validity of the relationships. We discuss the implications and possible neural mechanisms underlying these novel findings.


Asunto(s)
Emociones , Reconocimiento Facial , Polimorfismo de Nucleótido Simple , Proteínas de Transporte de Serotonina en la Membrana Plasmática/genética , Adolescente , Adulto , Femenino , Heterocigoto , Humanos , Masculino , Conducta Social
11.
Neurosci Lett ; 619: 172-6, 2016 Apr 21.
Artículo en Inglés | MEDLINE | ID: mdl-27012426

RESUMEN

Loss aversion is a decision bias, reflecting a greater sensitivity to losses than to gains in a decision situation. Recent neuroscientific research has shown that mesocorticolimbic structures like ventromedial prefrontal cortex and the ventral striatum constitute a bidirectional neural system that processes gains and losses and exhibits a neural basis of loss aversion. On a functional and structural level, the amygdala and insula also seem to play an important role in the processing of loss averse behavior. By applying voxel-based morphometry to structural brain images in N=41 healthy participants, the current study provides further evidence for the relationship of brain structure and loss aversion. The results show a negative correlation of gray matter volume in bilateral posterior insula as well as left medial frontal gyrus with individual loss aversion. Hence, higher loss aversion is associated with lower gray matter volume in these brain areas. Both structures have been discussed to play important roles in the brain's salience network, where the posterior insula is involved in interoception and the detection of salience. The medial frontal gyrus might impact decision making through its dense connections with the anterior cingulate cortex. A possible explanation for the present finding is that structural differences in these regions alter the processing of losses and salience, possibly biasing decision making towards avoidance of negative outcomes.


Asunto(s)
Anticipación Psicológica , Corteza Cerebral/patología , Toma de Decisiones , Adulto , Amígdala del Cerebelo/patología , Femenino , Juego de Azar/patología , Sustancia Gris/patología , Humanos , Imagen por Resonancia Magnética , Masculino , Tamaño de los Órganos , Corteza Prefrontal/patología , Adulto Joven
12.
Mucosal Immunol ; 9(1): 13-23, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25943275

RESUMEN

There have been encouraging results for the development of an effective HIV vaccine. However, many questions remain regarding the quality of immune responses and the role of mucosal antibodies. We addressed some of these issues by using a simian immunodeficiency virus (SIV) DNA vaccine adjuvanted with plasmid-expressed mucosal chemokines combined with an intravaginal SIV challenge in rhesus macaque (RhM) model. We previously reported on the ability of CCR9 and CCR10 ligand (L) adjuvants to enhance mucosal and systemic IgA and IgG responses in small animals. In this study, RhMs were intramuscularly immunized five times with either DNA or DNA plus chemokine adjuvant delivered by electroporation followed by challenge with SIVsmE660. Sixty-eight percent of all vaccinated animals (P<0.01) remained either uninfected or had aborted infection compared with only 14% in the vaccine naïve group. The highest protection was observed in the CCR10L chemokines group, where six of nine animals had aborted infection and two remained uninfected, leading to 89% protection (P<0.001). The induction of mucosal SIV-specific antibodies and neutralization titers correlated with trends in protection. These results indicate the need to further investigate the contribution of chemokine adjuvants to modulate immune responses and the role of mucosal antibodies in SIV/HIV protection.


Asunto(s)
Vacunas contra el SIDA/administración & dosificación , Anticuerpos Antivirales/biosíntesis , Quimiocinas/inmunología , Inmunidad Mucosa/efectos de los fármacos , Síndrome de Inmunodeficiencia Adquirida del Simio/prevención & control , Vacunas de ADN/administración & dosificación , Vacunas contra el SIDA/genética , Vacunas contra el SIDA/inmunología , Adyuvantes Inmunológicos/administración & dosificación , Animales , Quimiocinas/administración & dosificación , Quimiocinas/genética , Femenino , Inmunidad Celular/efectos de los fármacos , Ligandos , Macaca mulatta , Plásmidos/química , Plásmidos/inmunología , Receptores CCR/genética , Receptores CCR/inmunología , Receptores CCR10/genética , Receptores CCR10/inmunología , Síndrome de Inmunodeficiencia Adquirida del Simio/inmunología , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/efectos de los fármacos , Virus de la Inmunodeficiencia de los Simios/inmunología , Vacunación , Vacunas de ADN/genética , Vacunas de ADN/inmunología , Vagina/efectos de los fármacos , Vagina/inmunología , Vagina/virología
13.
J Commun Disord ; 58: 119-25, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26547120

RESUMEN

Two recent studies from Australia and Germany have both shown that people who stutter (PWS) have elevated Neuroticism scores on the widely used NEO Five Factor Inventory (NEO-FFI) compared to individuals in a control sample. The two studies showed opposite results, however, for the personality traits Agreeableness and Conscientiousness. One reason for these opposing findings could be that the two studies were conducted in different cultural settings. Given that the effect of different cultural background on the relationship between the NEO-FFI and stuttering remains an open question, we investigated the NEO-FFI scores from 98 PWS and an age- and sex-matched control-group from a less widely studied cultural background (Iran). Overall, the present study showed, in line with a study from Germany, higher Agreeableness, but not Neuroticism, in PWS compared to normally fluent controls. To get further insights into these findings, we also contrasted both samples from Iran with a healthy matched sample from Germany. The resulting cross-cultural differences from these analyses are also discussed in the present paper. Although the present study is limited by a cross-sectional design, and so no causal conclusions can be drawn, the authors discuss whether the replicated elevated Agreeableness scores in PWS might represent a self-defense mechanism to cope with one's own speech handicap.


Asunto(s)
Personalidad , Tartamudeo/psicología , Adolescente , Adulto , Estudios Transversales , Femenino , Humanos , Irán , Masculino , Modelos Psicológicos , Pruebas de Personalidad , Adulto Joven
14.
AJNR Am J Neuroradiol ; 36(12): 2277-84, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26381562

RESUMEN

BACKGROUND AND PURPOSE: As yet, there are no in vivo data on tissue water changes and associated morphometric changes involved in the osmo-adaptation of normal brains. Our aim was to evaluate osmoadaptive responses of the healthy human brain to osmotic challenges of de- and rehydration by serial measurements of brain volume, tissue fluid, and metabolites. MATERIALS AND METHODS: Serial T1-weighted and (1)H-MR spectroscopy data were acquired in 15 healthy individuals at normohydration, on 12 hours of dehydration, and during 1 hour of oral rehydration. Osmotic challenges were monitored by serum measures, including osmolality and hematocrit. MR imaging data were analyzed by using FreeSurfer and LCModel. RESULTS: On dehydration, serum osmolality increased by 0.67% and brain tissue fluid decreased by 1.63%, on average. MR imaging morphometry demonstrated corresponding decreases of cortical thickness and volumes of the whole brain, cortex, white matter, and hypothalamus/thalamus. These changes reversed during rehydration. Continuous fluid ingestion of 1 L of water for 1 hour within the scanner lowered serum osmolality by 0.96% and increased brain tissue fluid by 0.43%, on average. Concomitantly, cortical thickness and volumes of the whole brain, cortex, white matter, and hypothalamus/thalamus increased. Changes in brain tissue fluid were related to volume changes of the whole brain, the white matter, and hypothalamus/thalamus. Only volume changes of the hypothalamus/thalamus significantly correlated with serum osmolality. CONCLUSIONS: This is the first study simultaneously evaluating changes in brain tissue fluid, metabolites, volume, and cortical thickness. Our results reflect cellular volume regulatory mechanisms at a macroscopic level and emphasize that it is essential to control for hydration levels in studies on brain morphometry and metabolism in order to avoid confounding the findings.


Asunto(s)
Encéfalo/patología , Deshidratación/patología , Fluidoterapia , Líquidos Corporales/metabolismo , Encéfalo/metabolismo , Deshidratación/metabolismo , Humanos , Imagen por Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética , Espectroscopía de Protones por Resonancia Magnética , Agua/metabolismo
15.
Phys Rev Lett ; 115(5): 055002, 2015 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-26274425

RESUMEN

We present few-femtosecond shadowgraphic snapshots taken during the nonlinear evolution of the plasma wave in a laser wakefield accelerator with transverse synchronized few-cycle probe pulses. These snapshots can be directly associated with the electron density distribution within the plasma wave and give quantitative information about its size and shape. Our results show that self-injection of electrons into the first plasma-wave period is induced by a lengthening of the first plasma period. Three-dimensional particle-in-cell simulations support our observations.

16.
Nat Mater ; 14(8): 820-5, 2015 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-26168344

RESUMEN

Nanowire growth by the vapour-liquid-solid (VLS) process enables a high level of control over nanowire composition, diameter, growth direction, branching and kinking, periodic twinning, and crystal structure. The tremendous impact of VLS-grown nanowires is due to this structural versatility, generating applications ranging from solid-state lighting and single-photon sources to thermoelectric devices. Here, we show that the morphology of these nanostructures can be further tailored by using the liquid droplets that catalyse nanowire growth as a 'mixing bowl', in which growth materials are sequentially supplied to nucleate new phases. Growing within the liquid, these phases adopt the shape of faceted nanocrystals that are then incorporated into the nanowires by further growth. We demonstrate this concept by epitaxially incorporating metal-silicide nanocrystals into Si nanowires with defect-free interfaces, and discuss how this process can be generalized to create complex nanowire-based heterostructures.

17.
Small ; 10(14): 2849-58, 2014 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-24634208

RESUMEN

For the first time, it is demonstrated that nanoscale HfO2 surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO2 -based anodes. Specifically, the measured battery capacity at a current density of 150 mAg(-1) after 100 cycles is 548 and 853 mAhg(-1) for the uncoated and HfO2 -coated anodes, respectively. Material analysis reveals that the HfO2 layers are amorphous in nature and conformably coat the SnO2 -based anodes. In addition, the analysis reveals that ALD HfO2 not only protects the SnO2 -based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO2 anodes to increase battery capacity, despite the fact that HfO2 is itself electrochemically inactive. The amorphous nature of HfO2 is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity.

18.
Science ; 343(6168): 281-4, 2014 Jan 17.
Artículo en Inglés | MEDLINE | ID: mdl-24436416

RESUMEN

In the growth of nanoscale device structures, the ultimate goal is atomic-level precision. By growing III-V nanowires in a transmission electron microscope, we measured the local kinetics in situ as each atomic plane was added at the catalyst-nanowire growth interface by the vapor-liquid-solid process. During growth of gallium phosphide nanowires at typical V/III ratios, we found surprising fluctuations in growth rate, even under steady growth conditions. We correlated these fluctuations with the formation of twin defects in the nanowire, and found that these variations can be suppressed by switching to growth conditions with a low V/III ratio. We derive a growth model showing that this unexpected variation in local growth kinetics reflects the very different supply pathways of the V and III species. The model explains under which conditions the growth rate can be controlled precisely at the atomic level.

19.
Naturwissenschaften ; 100(9): 895-8, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23949307

RESUMEN

Several social mammals, including elephants and some primates, whales and bats, live in multilevel societies that form temporary subgroups. Despite these fission-fusion dynamics, group members often maintain long-term bonds. However, it is unclear whether such individual links and the resulting stable social subunits continue to exist after a complete reorganisation of a society, e.g. following a population crash. Here, we employed a weighted network analysis on 7,109 individual roosting records collected over 4 years in a wild Bechstein's bat colony. We show that, in response to a strong population decline, the colony's two stable social subunits fused into a non-modular social network. Nevertheless, in the first year after the crash, long-term bonds were still detectable, suggesting that the bats remembered previous individual relationships. Our findings are important for understanding the flexibility of animal societies in the face of dramatic changes and for the conservation of social mammals with declining populations.


Asunto(s)
Conducta Animal , Quirópteros/fisiología , Conducta Social , Animales , Femenino , Masculino , Dinámica Poblacional
20.
J Appl Microbiol ; 115(5): 1212-21, 2013 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23910098

RESUMEN

AIMS: To develop a staining method for specific detection of metabolically active (viable) cells in biofilms of the foodborne pathogen Campylobacter jejuni. METHODS AND RESULTS: Conversion of 2,3,5 triphenyltetrazolium chloride (TTC) to insoluble, red 1,3,5-triphenylformazan (TPF) was dependent on metabolic activity of Camp. jejuni. When used with chicken juice, TTC staining allowed quantification of Camp. jejuni biofilm levels, whereas the commonly used dye, crystal violet, gave high levels of nonspecific staining of food matrix components (chicken juice). The assay was optimized to allow for monitoring of biofilm levels and adapted to monitor levels of Camp. jejuni in broth media. CONCLUSIONS: Staining with TTC allows for the quantification of metabolically active Camp. jejuni and thus allows for quantification of viable cells in biofilms and food matrices. The TTC staining method can be adapted to quantify bacterial cell concentration in a food matrix model, where the accepted method of A600 measurement is not suitable due to interference by components of the food matrix. SIGNIFICANCE AND IMPACT OF THE STUDY: 2,3,5 Triphenyltetrazolium chloride (TTC) staining is a low-cost technique suitable for use in biofilm analysis, allowing rapid and simple imaging of metabolically active cells and increasing the methods available for biofilm assessment and quantification.


Asunto(s)
Biopelículas , Campylobacter jejuni/metabolismo , Contaminación de Alimentos/análisis , Microbiología de Alimentos/métodos , Coloración y Etiquetado/métodos , Sales de Tetrazolio/metabolismo , Animales , Campylobacter jejuni/crecimiento & desarrollo , Pollos/microbiología , Formazáns/metabolismo , Violeta de Genciana , Carne/microbiología , Viabilidad Microbiana , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
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