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1.
J Sports Sci ; : 1-12, 2024 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-38293847

RESUMO

Ecological approaches in sport consider that athletes adapt to properties of the task and the surrounding environment. Thus, task and environment are key constraints of performance. Yet, the influence of task and environmental constraints on athletes' performance needs empirical examination, especially in sport-specific contexts such as soccer goalkeeping. This study aimed to examine if and how task and environmental constraints influenced goalkeepers (GKs') performances. We monitored performance coefficients of two professional female GKs across 13 training tasks that varied based on 9 constraints, referring to both interactions among athletes and properties of the surrounding landscape. Results showed that constraints explain ~ 47% of the observed variability in GKs' performances. Numerical complexity (i.e., the potential interactions between athletes) showed a major influence on performance, which indicates that number of interactions among athletes may constrain GKs' perceived opportunities for action. Field dimensions and landscape representativity (including elements such as penalty area(s), target goal(s) and constraints for shooting) showed positive relationships with performance, supporting that training designs retaining closer proximity to the game may benefit GKs' performances. Overall, results supported that athlete-environment couplings could be understood as a multifactorial model and hence, a combination of task constraints are necessary for designing effective learning environments.

2.
J Cardiovasc Electrophysiol ; 34(9): 1802-1807, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37473404

RESUMO

INTRODUCTION: Pulsed-field ablation (PFA) and the multielectrode radiofrequency balloon (RFB) are two novel ablation technologies to perform pulmonary vein isolation (PVI). It is currently unknown whether these technologies differ in lesion formation and lesion extent. We compared the acute lesion extent after PVI induced by PFA and RFB by measuring low-voltage area in high-density maps and the release of biomolecules reflecting cardiac injury. METHODS: PVI was performed with a pentaspline catheter (FARAPULSE) applying PFA or with the compliant multielectrode RFB (HELIOSTAR). Before and after PVI high-density mapping with CARTO 3 was performed. In addition, blood samples were taken before transseptal puncture and after post-PVI remapping and serum concentrations of high-sensitive Troponin I were quantified by immunoassay. RESULTS: Sixty patients undergoing PVI by PFA (n = 28, age 69 ± 12 year, 60% males, 39.3% persistent atrial fibrillation [AF]) or RFB (n = 32, age 65 ± 13 year, 53% males, 21.9% persistent AF) were evaluated. Acute PVI was achieved in all patients in both groups. Mean number of PFA pulses was 34.2 ± 4.5 and mean number RFB applications was 8.5 ± 3 per patient. Total posterior ablation area was significantly larger in PFA (20.7 ± 7.7 cm²) than in RFB (7.1 ± 2.09 cm²; p < .001). Accordingly, posterior ablation area for each PV resulted in larger lesions after PFA versus RFB (LSPV 5.2 ± 2.7 vs. 1.9 ± 0.8 cm², LIPV 5.5 ± 2.3 vs. 1.9 ± 0.8 cm², RSPV 4.7 ± 1.9 vs. 1.6 ± 0.5 cm², RIPV 5.3 ± 2.1 vs. 1.6 ± 0.7 cm,² respectively; p < .001). In a subset of 38 patients, increase of hsTropI was higher after PFA (625 ± 138 pg/mL, n = 28) versus RFB (148 ± 36 pg/mL, n = 10; p = .049) supporting the evidence of larger lesion extent by PFA. CONCLUSION: PFA delivers larger acute lesion areas and higher troponin release upon successful PVI than multielectrode RFB-based PVI in this single-center series.


Assuntos
Fibrilação Atrial , Ablação por Cateter , Veias Pulmonares , Masculino , Humanos , Pessoa de Meia-Idade , Idoso , Idoso de 80 Anos ou mais , Feminino , Veias Pulmonares/cirurgia , Resultado do Tratamento , Ablação por Cateter/efeitos adversos , Ablação por Cateter/métodos , Fibrilação Atrial/diagnóstico , Fibrilação Atrial/cirurgia , Catéteres
3.
Alzheimer Dis Assoc Disord ; 34(3): 198-205, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32427599

RESUMO

BACKGROUND: Subjective cognitive decline (SCD) may represent a low-burden indicator of dementia risk. The value of SCD as a proxy marker, however, depends on the consistency of associations between subjective and objective cognitive measures across sociodemographic and psychological factors. METHODS: We evaluated baseline data from the Kaiser Healthy Aging and Diverse Life Experiences (KHANDLE) study (n=1615). SCD was measured using the 12-item Everyday Cognition (ECog) scale. Using linear regression models with interaction terms, we evaluated 6 potential modifiers (age, sex, race/ethnicity, educational attainment, family history of dementia, and depressive symptoms) of the association between cognitive performance (episodic memory, executive function) and SCD. RESULTS: Lower episodic memory and executive function scores were associated with higher log(ECog scores) (more SCD). Older age and elevated depressive symptoms were associated with higher log(ECog scores). Age (interaction P=0.002) and education (interaction P=0.01) modified the association between executive function and log(ECog scores). Specifically, associations between executive function and log(ECog scores) were stronger among participants with more education and less pronounced among older participants. CONCLUSIONS: The association between cognitive performance and log(ECog scores) differed little across sociodemographic and psychological factors. SCD as measured by the ECog may be a valuable proxy for cognitive performance in diverse older adults.


Assuntos
Disfunção Cognitiva , Etnicidade/estatística & dados numéricos , Testes Neuropsicológicos/estatística & dados numéricos , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , California , Disfunção Cognitiva/etnologia , Disfunção Cognitiva/psicologia , Estudos de Coortes , Feminino , Humanos , Vida Independente , Masculino , Fatores Sexuais
4.
J Sports Sci ; 38(11-12): 1465-1473, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31311425

RESUMO

The football goalkeeper position arguably represents a unique role within the team sport. Despite its highly complex skill demands, research on football goalkeeping has only sporadically examined the position within isolated and limited parameters. In particular, there is limited literature on "modern" skill acquisition training methods and approaches within the field of goalkeeper training. In a cross-cultural study with fifteen expert goalkeeper coaches, researchers here examined the overarching research question of "how does the modern football goalkeeper train?". Semi-structured interviews explored expert coaches' views on critical skills for performance in goalkeeping and the training approaches used to develop these critical skills. Results indicate that four skill sets are considered essential by goalkeeper coaches, these are: decision-making skills, athleticism, mentality, and technical skills. In terms of developing these skills in goalkeeper-specific training, the majority of expert coaches apply a similar microstructure to training sessions. This structure involves a steady progression from simple to complex training tasks, where for large parts, isolated technical training appears to be prioritised over a holistic training approach that integrates technical skills and perceptual-cognitive components (e.g., decision making). Scientific and practical recommendations for researchers and practitioners in the field of football goalkeeper coaching are provided.


Assuntos
Desempenho Atlético/psicologia , Destreza Motora , Condicionamento Físico Humano/métodos , Futebol/psicologia , Adulto , Tomada de Decisões , Humanos , Tutoria , Pesquisa Qualitativa
5.
Phys Chem Chem Phys ; 17(13): 8467-79, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25660666

RESUMO

Density functional theory (B3LYP-D3, M06-2X) has been used to calculate the structures, interaction energies and vibrational frequencies of a set of 93 methanol-water clusters of different type (cubic, ring, spiro, lasso, bicyclic), size and composition. These interaction energies have been used within the framework of the Quantum Cluster Equilibrium Theory (QCE) to calculate cluster populations as well as thermodynamic properties of binary methanol-water mixtures spanning the whole range from pure water to pure methanol. The necessary parameters amf and bxv of the QCE model were obtained by fitting to experimental isobars of MeOH-H2O mixtures with different MeOH content. The cubic and spiro motifs dominate the distribution of methanol-water clusters in the mixtures with a maximum of mixed clusters at x(MeOH) = 0.365. Reasonable agreement with experimental data as well as earlier molecular dynamics simulations was found for excess enthalpies H(E), entropies S(E) as well as Gibbs free energies of mixing G(E). In contrast, heat capacities Cp and C showed only poor agreement with experimental data.

6.
Clin Immunol ; 152(1-2): 20-4, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24607792

RESUMO

B cells are increasingly coming into play in the pathogenesis of multiple sclerosis (MS). Here, we screened peripheral blood mononuclear cells (PBMC) from patients with clinically isolated syndrome (CIS), MS, other non-inflammatory neurological, inflammatory neurological or autoimmune diseases, and healthy donors for their B cell reactivity to CNS antigen using the enzyme-linked immunospot technique (ELISPOT) after 96 h of polyclonal stimulation. Our data show that nine of 15 patients with CIS (60.0%) and 53 of 67 patients with definite MS (79.1%) displayed CNS-reactive B cells, compared to none of the control donors. The presence of CNS-reactive B cells in the blood of the majority of patients with MS or at risk to develop MS along with their absence in control subjects suggests that they might be indicative of a B cell-dependent subpopulation of the disease.


Assuntos
Linfócitos B/imunologia , Sistema Nervoso Central/imunologia , Doenças Desmielinizantes/imunologia , Esclerose Múltipla/imunologia , Adulto , Linfócitos B/citologia , Feminino , Humanos , Leucócitos Mononucleares/imunologia , Masculino
7.
Sci Rep ; 13(1): 20497, 2023 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-37993550

RESUMO

Dendritic spines are considered a morphological proxy for excitatory synapses, rendering them a target of many different lines of research. Over recent years, it has become possible to simultaneously image large numbers of dendritic spines in 3D volumes of neural tissue. In contrast, currently no automated method for 3D spine detection exists that comes close to the detection performance reached by human experts. However, exploiting such datasets requires new tools for the fully automated detection and analysis of large numbers of spines. Here, we developed an efficient analysis pipeline to detect large numbers of dendritic spines in volumetric fluorescence imaging data acquired by two-photon imaging in vivo. The core of our pipeline is a deep convolutional neural network that was pretrained on a general-purpose image library and then optimized on the spine detection task. This transfer learning approach is data efficient while achieving a high detection precision. To train and validate the model we generated a labeled dataset using five human expert annotators to account for the variability in human spine detection. The pipeline enables fully automated dendritic spine detection reaching a performance slightly below that of the human experts. Our method for spine detection is fast, accurate and robust, and thus well suited for large-scale datasets with thousands of spines. The code is easily applicable to new datasets, achieving high detection performance, even without any retraining or adjustment of model parameters.


Assuntos
Espinhas Dendríticas , Tecido Nervoso , Humanos , Redes Neurais de Computação , Imageamento Tridimensional/métodos , Microscopia Confocal/métodos
8.
Front Psychol ; 13: 1020915, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36825240

RESUMO

Background: Cognitive inhibition is among the executive functions that decline early in the course of normal aging. Failures to be able to inhibit irrelevant information from memory may represent an essential factor of age-associated memory impairment. While a variety of elaborate behavioral tasks have been developed that presumably all index memory inhibition, the extent to which these different tasks measure the same underlying cognitive construct that declines with age has not been well explored. Methods: In the current study, 100 and 75 cognitively healthy younger (n = 71; age = 30.7 ± 5.4 years, 56.7% female) and older (n = 104, age = 69.3 ± 5.9 years, 66.2% female) adults with equivalent educational attainment performed three computer-based memory inhibition tasks: the Retrieval Induced Forgetting task, the Suppress task, and the Directed Forgetting task. We conducted a principal component analysis using scores derived from different components of these tasks to explore whether and how the tasks relate to one another. We further investigated how age, sex and education, along with, in a subsample of the participants, a neuropsychological measure of episodic memory, impacted both the task scores individually, and the principal components derived from the exploratory analysis. Results: We identified 3 distinct sources of variability which represent potentially independent cognitive processes: memory retrieval facilitation, and two memory inhibition processes that distinguished themselves by the degree of volitional initiation of memory suppression. Only the memory retrieval component correlated with a neuropsychologically-derived episodic memory score, and both memory inhibition principal components were age dependent. Conclusion: Our findings provide support for a distinction in memory suppression processes between those 'instructed' to be performed and those which happen without explicit instruction. This distinction adds nuance to the dichotomous classification of controlled vs. automatic inhibitory mechanisms, which have been shown in previous work to vary as a function of the degree of frontal involvement. Our findings further demonstrate that while both of these measures of inhibition were affected by age, the episodic memory component was not, suggesting that inhibitory impairments may precede memory deficits in healthy aging.

9.
Eur J Sport Sci ; 21(7): 1035-1044, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32781916

RESUMO

Stadium noise - created by spectators and fans - plays a critical part in the reality of professional sports. Due to a lack of research on the impact of these auditory cues and multimodal environments on motor performance, it is currently unclear how professional athletes experience and perceive stadium noise and how this potentially affects performance in practice. In order to explore the effect of stadium noise on athletes' performance, this paper presents an experimental design using the unique and standardised football training tool known as the "Footbonaut". Specifically, fifteen skilled German football players engaged in a standardised football-specific technical training programme while subjected to four different auditory training conditions; these included both "positive" and "negative" stadium noise conditions, a "baseline" condition providing auditory guidance, and a "no (auditory) cue" condition. Performance data for passing accuracy and passing time were measured for training in each auditory condition. A repeated measures MANOVA revealed a significant main effect for passing time. Specifically, participants showed faster passing times in the baseline compared to the negative and no auditory cue conditions. Findings are presented and discussed from a constraints-led perspective, allied to principles of ecological dynamics and nonlinear pedagogy. Particularly, the use of representative training experiences (including multimodal sensory and emotional information) appears to underline training to refine expert athletes' adaptive coordination of complex motor actions.


Assuntos
Desempenho Atlético/psicologia , Ruído , Exposição Ocupacional , Futebol/psicologia , Adolescente , Adulto , Percepção Auditiva/fisiologia , Sinais (Psicologia) , Humanos , Masculino , Condicionamento Físico Humano/fisiologia , Análise e Desempenho de Tarefas , Adulto Jovem
10.
Front Psychol ; 11: 1444, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760314

RESUMO

In specialist sports coaching, the type and manner of augmented information that the coach chooses to use in communicating and training with individual athletes can have a significant impact on skill development and performance. Informed by insights from psychology, pedagogy, and sport science, this position paper presents a practitioner-based approach in response to the overarching question: When, why, and how could coaches provide information to athletes during coaching interventions? In an ecological dynamics rationale, practice is seen as a search for functional performance solutions, and augmented feedback is outlined as instructional constraints to guide athletes' self-regulation of action in practice. Using the exemplar of team sports, we present a Skill Training Communication Model for practical application in the context of the role of a specialist coach, using a constraints-led approach (CLA). Further based on principles of a non-linear pedagogy and using the recently introduced Periodization of Skill Training (PoST) framework, the proposed model aims to support practitioners' understanding of the pedagogical constraints of feedback and instruction during practice. In detail, the PoST framework's three skill development and training stages work to (1) directly impact constraint manipulations in practice designs and (2) indirectly affect coaches' choices of external (coach-induced) information. In turn, these guide practitioners on how and when to apply different verbal instruction methodologies and aim to support the design of effective skill learning environments. Finally, several practical guidelines in regard to sports coaches' feedback and instruction processes are proposed.

11.
Sports Med Open ; 6(1): 55, 2020 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-33196910

RESUMO

With increasing resources in sports organisations being allocated to the development and preparation of individual athletes and sub-groups with specialist performance roles, the work of coaches, specialist (role) coaches and support staff needs to be functionally and coherently integrated. This integration of sport science support and coaching can be administered by staff in a Department of Methodology (DoM). Particularly, in this paper, we propose how specialist coaching can be situated in a DoM, presenting a model advocating effective functioning in high-performance team sports organisations. Using principles of ecological dynamics, we provide a rationale for a functional methodology for the design of practice tasks in a DoM that views learners as wayfinders, self-regulating their way through competitive performance environments. This rationale for athlete self-regulation in practice could improve athlete performance by enhancing problem solving, engagement with constraints of learning designs and supporting better attunement to contextual information abundant in a competitive environment. Finally, by introducing this unified and multidisciplinary DoM, specialist coaches, team coaches and sport science support staff, within the organisational structure, can collaboratively debate and co-design individualised athlete training programmes to enrich skill adaptability and performance functionality. To underline these contentions, three high-performance sport case studies from Australian Football: goalkeeping in Association Football and Rugby League are presented.

12.
Artigo em Inglês | MEDLINE | ID: mdl-33344984

RESUMO

Across sports and movement science, training periodization has been recognized as key for athlete development and performance. While periodization with regard to physiology has a proven history, the structuring and periodization of motor learning and skill development is seemingly less researched and practiced. Despite the existence of numerous theoretical accounts underpinning skill acquisition training and more recently emerging periodization models, a cohesive framework to practically support coaches in the context of "specialist coaching" appears to be needed. The use of "specialist coaches" for individualized, one-on-one or small group trainings displays a growing trend in team ball sports. Despite limiting the replication of game-representative environments (i.e., by constraining the number of involved athletes in training), "specialist coaches" in performance sport constantly aim to achieve marginal gains and refinements in athlete development. In order to support these "specialist coaches" and fill a research gap on skill training periodization, the current paper seeks to review and transfer contemporary skill acquisition training theory (driven by the constraints-led approach) into a practically-applicable "Periodization of Skill Training" framework ("PoST" framework). This framework provides valuable conceptual and practical support for "specialist coaches" in performance sport; which will in turn, enhance, and refine adaptive movement variability for sport skills and manipulate skill training environments (i.e., over the course of macro- and micro-cycles, and for the planning of single training sessions). Practical examples from soccer goalkeeping (i.e., a "specialist coaching" context, often constrained to a small number of players in the training environment) will underline the proposed framework.

13.
Circulation ; 100(11): 1242-8, 1999 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-10484547

RESUMO

A wide variety of pharmacological agents are currently used for prevention of recurrent neurally mediated syncope, especially the vasovagal faint. None, however, have unequivocally proven long-term effectiveness based on adequate randomized clinical trials. At the present time, beta-adrenergic receptor blockade, along with agents that increase central volume (eg, fludrocortisone, electrolyte-containing beverages), appear to be favored treatment options. The antiarrhythmic agent disopyramide and various serotonin reuptake blockers have also been reported to be beneficial. Finally, vasoconstrictor agents such as midodrine offer promise and remain the subject of clinical study. Ultimately, though, detailed study of the pathophysiology of these syncopal disorders and more aggressive pursuit of carefully designed placebo-controlled treatment studies are essential if pharmacological prevention of recurrent neurally mediated syncope is to be placed on a firm foundation.


Assuntos
Síncope/tratamento farmacológico , Antagonistas Adrenérgicos beta/uso terapêutico , Humanos , Antagonistas da Serotonina/uso terapêutico , Vasoconstritores/uso terapêutico
14.
Nat Commun ; 6: 7027, 2015 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-25960367

RESUMO

Silicon photonics holds great promise for low-cost large-scale photonic integration. In its future development, integration density will play an ever-increasing role in a way similar to that witnessed in integrated circuits. Waveguides are perhaps the most ubiquitous component in silicon photonics. As such, the density of waveguide elements is expected to have a crucial influence on the integration density of a silicon photonic chip. A solution to high-density waveguide integration with minimal impact on other performance metrics such as crosstalk remains a vital issue in many applications. Here, we propose a waveguide superlattice and demonstrate advanced superlattice design concepts such as interlacing-recombination that enable high-density waveguide integration at a half-wavelength pitch with low crosstalk. Such waveguide superlattices can potentially lead to significant reduction in on-chip estate for waveguide elements and salient enhancement of performance for important applications, opening up possibilities for half-wavelength-pitch optical-phased arrays and ultra-dense space-division multiplexing.

15.
Clin Pharmacokinet ; 22 Suppl 1: 33-42, 1992.
Artigo em Inglês | MEDLINE | ID: mdl-1319869

RESUMO

The biliary excretion of temafloxacin and temafloxacin glucuronide was characterised in this study after administration of a single oral temafloxacin 600mg dose to 8 patients with T-tube drainage of the common bile duct inserted after cholecystectomy or choledochotomy. High performance liquid chromatographic analyses of plasma, urine and bile samples collected during the 72h after temafloxacin administration showed that biliary concentrations of unchanged temafloxacin followed a time-course parallel to plasma concentrations but were 5- to 10-fold higher. Biliary temafloxacin peak concentrations ranged from 18.74 to 64.35 mg/L and time to peak concentrations from 0.71 to 10.23h. Mean hepatobiliary clearance of temafloxacin was 3.10 ml/min (0.19 L/h) when calculated for the unchanged drug and 1.43 ml/min (0.09 L/h) when calculated for its biliary excretion as glucuronic acid conjugates. Patients with higher bile production had markedly higher clearance of both temafloxacin and temafloxacin glucuronide. The elimination time-course of the conjugate in bile generally paralleled those of temafloxacin in bile and plasma, although there was a lag in the rate of appearance of the conjugate in bile. Biliary excretion of unchanged temafloxacin and temafloxacin glucuronide accounted for approximately 2.2 and 1% of the administered dose, respectively. Thus, it appears that hepatobiliary elimination of temafloxacin and its glucuronide acid accounts for only a small fraction of total temafloxacin clearance. Nonetheless, concentrations attained in the bile are far above the minimum inhibitory concentration values of pathogens relevant in biliary tract infections.


Assuntos
Anti-Infecciosos/farmacocinética , Bile/química , Fluoroquinolonas , Fígado/metabolismo , Quinolonas/farmacocinética , Administração Oral , Adulto , Idoso , Anti-Infecciosos/administração & dosagem , Colecistectomia , Cromatografia Líquida de Alta Pressão , Feminino , Humanos , Fígado/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Quinolonas/administração & dosagem
16.
Clin Pharmacokinet ; 22 Suppl 1: 24-32, 1992.
Artigo em Inglês | MEDLINE | ID: mdl-1319868

RESUMO

A multicentre study was conducted to determine whether liver impairment would alter the pharmacokinetics of temafloxacin, a new fluoroquinolone antimicrobial agent. 16 patients with cirrhosis and 12 healthy volunteers (the control group) received a single oral 600mg dose of temafloxacin. Blood and urine were sampled at frequent intervals after drug administration and assayed by high performance liquid chromatography. The mean age of patients with liver impairment was greater than that of the control group; they also had a lower creatinine clearance and urine output. There was no difference between the groups in either the peak plasma temafloxacin concentration or the time to reach peak concentration. However, the volume of distribution and elimination rate constant of temafloxacin were significantly lower in the group with liver impairment, as were total temafloxacin clearance, renal clearance, and the ratio of renal:creatinine clearance. Nonrenal clearance was similar in patients and controls. Creatinine clearance and urine output were found to account for most of the intersubject variability in total clearance as determined by multiple linear regression analysis. Because the altered temafloxacin pharmacokinetics appear to be primarily due to impaired renal function, this should be the main determinant of temafloxacin dosage in patients with liver disease.


Assuntos
Anti-Infecciosos/farmacocinética , Fluoroquinolonas , Cirrose Hepática/metabolismo , Quinolonas/farmacocinética , Adulto , Idoso , Anti-Infecciosos/sangue , Anti-Infecciosos/urina , Cromatografia Líquida de Alta Pressão , Feminino , Humanos , Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Quinolonas/sangue , Quinolonas/urina
17.
J Chromatogr A ; 992(1-2): 151-7, 2003 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-12735471

RESUMO

For a broad spectrum of simple chiral alcohols, incorporating a (substituted) (het)aryl building block, enantiomer separation characteristics are reported for both gas chromatography on a Chirasil-DEX phase, and liquid chromatography on an (S,S)-ULMO phase. On this chiral Pirkle-type phase, homochiral enantiomers (mostly R) are eluted first without exception. The elution order R before S appears conserved as a rule also for gas chromatographic separations on Chirasil-DEX, though with some remarkable exceptions indicating a change in the dominant discriminative mechanism. This was shown in the homologous series 1-phenylethanol to 1-phenylhexanol having the point of reversal at C4, while the o-methoxy analogues elute from C1 to C4 already in the reversed order.


Assuntos
Cromatografia Gasosa/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , Metanol/isolamento & purificação , Metanol/química , Espectrofotometria Ultravioleta , Estereoisomerismo
18.
J Chromatogr A ; 922(1-2): 13-23, 2001 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-11486858

RESUMO

Quantitative structure-retention (QSRR, retention factors log k1 and log k2 for the first and second eluted enantiomer) as well as enantioselective retention relationships (QSERR, separation factor log a) for a series of 42 chiral arylalkylcarbinols on four brush-type chiral stationary phases are derived by multiple linear regression analyses and artificial neuronal network calculations using 2D and 3D molecular descriptors including those obtained by quantum chemical calculations. Separation factors are in addition modeled by the 3D-QSAR method of comparative molecular field analysis (CoMFA). For the retention factors the LUMO energy turns out to be the most important descriptor, whereas for log a it is the hydrophobicity of the analytes. With CoMFA both the steric and electrostatic field are found to be of almost comparable significance.


Assuntos
Cromatografia Líquida/métodos , Metanol/isolamento & purificação , Cromatografia Líquida/instrumentação , Relação Estrutura-Atividade
19.
Cardiol Clin ; 15(2): 165-76, 1997 May.
Artigo em Inglês | MEDLINE | ID: mdl-9164708

RESUMO

Effective management of the syncope patient is critically dependent on excluding conditions in which altered consciousness is not due to syncope (e.g., seizure and sleep disorders) then establishing the basis for syncopal symptoms. The initial diagnostic step in syncope patients is differentiation of those individuals with normal cardiovascular status from those with structural heart disease. In the former, tilt-table testing and related studies of autonomic nervous system function are usually the most productive direction in which to proceed. In patients with structural heart disease, a functional assessment of the suspected structural disturbance (i.e., hemodynamic, angiographic, imaging as appropriate) and evaluation for susceptibility to symptomatic arrhythmias by monitoring or conventional electrophysiologic testing is appropriate. Autonomic function testing should follow if the diagnosis remains unclear. In only a few instances should specialized neurologic studies be undertaken as an initial step. The ultimate objective is always to obtain a sufficiently strong correlation between syncopal symptoms and detected abnormalities to feel confident in the diagnosis, permit an accurate assessment of prognosis, and develop an appropriate treatment plan.


Assuntos
Síncope/diagnóstico , Doenças Cardiovasculares/complicações , Ecocardiografia/métodos , Eletrocardiografia/métodos , Humanos , Pneumopatias/complicações , Transtornos Mentais/complicações , Síncope/classificação , Síncope/etiologia , Teste da Mesa Inclinada
20.
J Interv Card Electrophysiol ; 2(1): 25-32, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9869993

RESUMO

Vasovagal syncope is characterized by transient failure of usually reliable physiologic mechanisms responsible for maintaining both systemic arterial pressure and cerebral blood flow. Two circulatory phenomena are almost universally present: systemic arterial vasodilation and bradycardia. A third phenomenon, cerebrovascular constriction, has also been described but its contribution to the faint is less well established. The neural reflex pathways responsible for triggering the circulatory changes in the vasovagal faint are incompletely understood, but have recently been the subject of renewed interest. In part, this interest probably stems from the frequency with which vasovagal symptoms are now recognized to be the cause of fainting spells. Additionally, however, there is an increasingly recognized need to develop treatment strategies for those affected patients in whom recurrent vasovagal symptoms are particularly troublesome. It is the goal of this discussion to focus on those aspects of circulatory control, and in particular on potential interactions among certain neural and humoral systems, which may contribute to the inappropriate physiologic responses associated with the vasovagal faint.


Assuntos
Pressão Sanguínea/fisiologia , Frequência Cardíaca/fisiologia , Síncope Vasovagal/fisiopatologia , Vias Aferentes/fisiopatologia , Bradicardia/fisiopatologia , Sistema Nervoso Central/fisiopatologia , Circulação Cerebrovascular/fisiologia , Suscetibilidade a Doenças , Vias Eferentes/fisiopatologia , Retroalimentação/fisiologia , Homeostase , Humanos , Pressorreceptores/fisiologia , Síncope Vasovagal/etiologia , Síncope Vasovagal/imunologia , Síncope Vasovagal/terapia , Vasodilatação/fisiologia
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