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1.
Colorectal Dis ; 22(9): 1169-1174, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32065472

RESUMO

AIM: The involvement of surgeons in major adverse outcomes can have a negative impact on their personal and professional lives, as well as on patient outcomes. Healthcare professionals involved in such incidents have been referred to as 'second victims'. We designed an online survey to study the impact of operative complications on surgeons' professional and personal lives. METHOD: An online survey of general, gastrointestinal, hepato-pancreato-biliary and vascular surgeons was conducted using the Twitter feed of the Association of Coloproctology of Great Britain and Ireland, the Association of Surgeons of Great Britain and Ireland and the European Society of Coloproctology over an 8-week period. RESULTS: Questionnaires were completed by 82 participants. Ninety-one per cent of respondents were consultant surgeons, 37% with more than 15 years' experience. Eighty-three per cent were colorectal surgeons. The majority of surgeons (95%) reported that their practice had been affected as a result of serious complications and 54% suggested that it had had a negative impact on their family life. Fifty-five per cent of respondents mentioned lack of support in their institution for healthcare professionals involved in adverse outcomes and an existing blame culture. Suggestions for improvement included mentoring (41%), counselling (38%), openness (66%), peer support groups (52%) and human factors training (32%). CONCLUSION: This survey highlights that the majority of surgeons involved in serious complications are adversely affected. Those involved in the running of surgical services need to improve support for surgeons in the aftermath of such events.


Assuntos
Cirurgiões , Consultores , Humanos , Inquéritos e Questionários , Reino Unido
2.
J Hosp Infect ; 122: 162-167, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35151765

RESUMO

OBJECTIVE: Surgical Site Infections (SSIs) are responsible for a significant economic burden as well as intangible costs suffered by the patient, with up to 60% deemed preventable. Colorectal patients are disproportionally affected by SSI due the risk of wound contamination with bowel content. We aimed to reduce the rate of superficial SSI after elective colorectal surgery using a bundle of evidence-based interventions. METHODS: An SSI prevention bundle was implemented in elective colorectal surgery, comprised of triclosan-coated sutures, 2% chlorhexidine skin preparation and use of warmed carbon dioxide (CO2) during laparoscopic procedures. The SSI reduction strategy was prospectively implemented and compared with historical controls. Our primary outcome measure was the overall rate of superficial SSI. Centres for Disease Control and Prevention criteria, which use microbiological evidence in conjunction with clinical features were used as the definition of SSI. RESULTS: The overall SSI rate was 27.4% in the pre-bundle group (N = 208) and 12.5% in the patients who received the SSI prevention bundle (N = 184) (adjusted odds ratio 0.38; confidence interval 0.21-0.67; P<0.001). The median time to SSI diagnosis was postoperative day 8. Overall patient length of stay (LOS) was unchanged from six days at baseline following implementation of the bundle. CONCLUSIONS: We have shown successful implementation of an SSI prevention bundle which has reduced superficial SSI rate. We recommend this SSI prevention bundle becomes standard practice in elective colorectal surgery and plan to extend the bundle to emergency general surgery.


Assuntos
Cirurgia Colorretal , Procedimentos Cirúrgicos do Sistema Digestório , Triclosan , Cirurgia Colorretal/efeitos adversos , Procedimentos Cirúrgicos Eletivos/efeitos adversos , Humanos , Infecção da Ferida Cirúrgica/tratamento farmacológico , Infecção da Ferida Cirúrgica/prevenção & controle
3.
J Hosp Infect ; 130: 131-137, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36087804

RESUMO

BACKGROUND: Surgical site infections (SSIs) are common after colorectal surgery, but most hospitals do not know their SSI rates. Approximately half of SSIs occur after discharge, and postdischarge surveillance is needed for accurate measurement. Perioperative care bundles are known to reduce SSI rates. PreciSSion is a collaboration between seven hospitals in the West of England. AIMS: To establish reliable SSI measurement after elective colorectal surgery using 30-day patient-reported outcome measures, and to implement an evidence-based four-point care bundle that had already demonstrated a reduction in the SSI rate in a local hospital. The bundle included: 2% chlorhexidine skin preparation, a second dose of antibiotic after 4 h, use of a dual-ring wound protector, and use of antibacterial sutures for abdominal wall closure. METHODS: The 30-day patient-reported SSI rate was determined using the Public Health England questionnaire, and response rates were recorded. The baseline SSI rate was measured from November 2019 to May 2020, and continued after implementation of the care bundle until March 2021. Bundle compliance was also measured. FINDINGS: The average questionnaire response rate was 81%, and average compliance was 92%, 96%, 79% and 85% for each element of the bundle. The baseline SSI rate was 8-30%. Six of seven hospitals reduced their SSI rate, and the regional average SSI rate almost halved from 18% (1447 patients) to 9.5% (1247 patients). CONCLUSION: A care bundle developed in a single hospital can be adopted in other hospitals, and a 50% reduction in SSI rate after elective colorectal surgery can be replicated in other hospitals within 18 months.


Assuntos
Cirurgia Colorretal , Pacotes de Assistência ao Paciente , Humanos , Cirurgia Colorretal/efeitos adversos , Infecção da Ferida Cirúrgica/epidemiologia , Infecção da Ferida Cirúrgica/prevenção & controle , Infecção da Ferida Cirúrgica/tratamento farmacológico , Assistência ao Convalescente , Alta do Paciente , Procedimentos Cirúrgicos Eletivos/efeitos adversos , Antibacterianos/uso terapêutico
4.
Science ; 216(4553): 1415-6, 1982 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-6178155

RESUMO

The oligonucleotide (2'-5') oligoadenylate that is induced in interferon-treated animal cells protects plant tissue from infection by the tobacco mosaic virus. This inhibition of virus multiplication was obtained at concentrations comparable to those affecting protein synthesis and antiviral activities in animal cells. After treatment with (2'-5') oligoadenylate, the multiplicability of tobacco mosaic virus was reduced by 80 to 90 percent as measured by enzyme-linked immunosorbent assay. These results, along with the observation that human interferon protects tobacco tissue from infection by tobacco mosaic virus, indicate that plants and animals may have a common pathway for virus resistance.


Assuntos
Nucleotídeos de Adenina/farmacologia , Oligonucleotídeos/farmacologia , Oligorribonucleotídeos/farmacologia , Vírus do Mosaico do Tabaco/efeitos dos fármacos , Animais , Células Cultivadas , Interferons/farmacologia , Cinética , Plantas Tóxicas , Nicotiana/microbiologia , Replicação Viral/efeitos dos fármacos
5.
Science ; 259(5101): 1614-6, 1993 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-8384375

RESUMO

Glucagon and the glucagon receptor are a primary source of control over blood glucose concentrations and are especially important to studies of diabetes in which the loss of control over blood glucose concentrations clinically defines the disease. A complementary DNA clone for the glucagon receptor was isolated by an expression cloning strategy, and the receptor protein was expressed in several kidney cell lines. The cloned receptor bound glucagon and caused an increase in the intracellular concentration of adenosine 3', 5'-monophosphate (cAMP). The cloned glucagon receptor also transduced a signal that led to an increased concentration of intracellular calcium. The glucagon receptor is similar to the calcitonin and parathyroid hormone receptors. It can transduce signals leading to the accumulation of two different second messengers, cAMP and calcium.


Assuntos
Glucagon/farmacologia , Fígado/metabolismo , Receptores dos Hormônios Gastrointestinais/fisiologia , Transdução de Sinais , Sequência de Aminoácidos , Animais , Cálcio/farmacologia , Linhagem Celular , Clonagem Molecular , Cricetinae , AMP Cíclico/metabolismo , Glucagon/metabolismo , Rim , Cinética , Dados de Sequência Molecular , Ratos , Receptores dos Hormônios Gastrointestinais/genética , Receptores dos Hormônios Gastrointestinais/metabolismo , Receptores de Glucagon , Transfecção
6.
J Crit Care ; 50: 31-35, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30471558

RESUMO

PURPOSE: To investigate the incidence, nature and risk factors for patient-reported alopecia in survivors of critical illness. MATERIALS AND METHODS: A multi-centre, mixed methods observational study in the intensive care units (ICU) of ten hospitals in Wales. All patients with an ICU stay of 5 days or more, able to give consent were included. Demographic variables and risk factors were collected. A pre-designed survey was completed at three months post-ICU discharge. Statistical analysis included numbers and percentages (categorical variables) and medians and interquartile ranges (continuous variables). Comparisons between patients with and without alopecia were made using Fisher's Exact test (categorical variables) and Mann Whitney U test (continuous variables). Multivariate logistic regression analysis was used to determine the risk factors for alopecia. RESULTS: The survey was completed by 123 patients with alopecia reported in 44 (36%) patients. The only risk factor for alopecia on analysis was sepsis / septic shock (p < .001; OR: 5.1, 95%CI: 2.1-12.4). CONCLUSIONS: Limited research exists examining the incidence, nature and risk factors for patient-reported alopecia in adult survivors of critical illness. The results of this study highlight the need to discuss the potential for alopecia with survivors of critical illness, who had sepsis / septic shock.


Assuntos
Alopecia/etiologia , Sepse/complicações , Sobreviventes , Idoso , Alopecia/fisiopatologia , Alopecia/psicologia , Estado Terminal , Feminino , Humanos , Incidência , Unidades de Terapia Intensiva/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Sepse/fisiopatologia , Sobreviventes/psicologia
7.
Age Ageing ; 37(1): 10-3, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18194966

RESUMO

Falls are a leading cause of mortality and morbidity in older adults. Physical, psychological and social consequences include injury, fall-related fear and loss of self-efficacy. In turn, these may result in decreased physical activity, reduced functional capacity, and increased risk of institutionalisation. Falls prevention exercise programmes (FPEP) are now widespread within the National Health Service, often part of multifactorial interventions, and are designed to minimise impairments that impact physical function, such as strength and balance. Assessment of the clinical efficacy of FPEPs has therefore focused on the measurement of physical function and rate of falls. Whilst important, this approach may be too narrow to capture the highly variable and multidimensional responses that individuals make to a fall and to a FPEP. We argue that the current focus may miss a paradoxical lack of or even deleterious impact on quality of life, despite a reduction in physical performance-related falls risk. We draw upon the Selective Optimisation and Compensation (SOC) model, developed by Paul and Margret Baltes, to explore how this paradox may be a result of the coping strategies adopted by individuals in response to a fall.


Assuntos
Acidentes por Quedas/prevenção & controle , Atividades Cotidianas/psicologia , Exercício Físico , Idoso Fragilizado , Adaptação Psicológica , Idoso , Idoso de 80 Anos ou mais , Bengala , Comportamento de Escolha , Estudos Transversais , Exercício Físico/psicologia , Idoso Fragilizado/psicologia , Serviços de Assistência Domiciliar , Humanos , Estilo de Vida , Limitação da Mobilidade , Modelos Psicológicos , Força Muscular , Aceitação pelo Paciente de Cuidados de Saúde , Inventário de Personalidade , Equilíbrio Postural , Qualidade de Vida/psicologia , Papel do Doente , Ajustamento Social
9.
Accid Anal Prev ; 40(1): 396-402, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18215574

RESUMO

Driver fatigue remains a significant cause of motor-vehicle accidents worldwide. New technologies are increasingly utilised to improve road safety, but there are no effective on-road measures for fatigue. While simulated driving tasks are sensitive, and simple performance tasks have been used in industrial fatigue management systems (FMS) to quantify risk, little is known about the relationship between such measures. Establishing a simple, on-road measure of fatigue, as a fitness-to-drive tool, is an important issue for road safety and accident prevention, particularly as many fatigue related accidents are preventable. This study aimed to measure fatigue-related performance decrements using a simple task (reaction time - RT) and a complex task (driving simulation), and to determine the potential for a link between such measures, thus improving FMS success. Fifteen volunteer participants (7 m, 8 f) aged 22-56 years (mean 33.6 years), underwent 26 h of supervised wakefulness before an 8h recovery sleep opportunity. Participants were tested using a 30-min interactive driving simulation test, bracketed by a 10-min psychomotor vigilance task (PVT) at 4, 8, 18 and 24h of wakefulness, and following recovery sleep. Extended wakefulness caused significant decrements in PVT and driving performance. Although these measures are clearly linked, our analyses suggest that driving simulation cannot be replaced by a simple PVT. Further research is needed to closely examine links between performance measures, and to facilitate accurate management of fitness to drive, which requires more complex assessments of performance than RT alone.


Assuntos
Condução de Veículo/psicologia , Fadiga/diagnóstico , Fadiga/etiologia , Análise e Desempenho de Tarefas , Adolescente , Adulto , Simulação por Computador , Fadiga/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Psicológicos , Valor Preditivo dos Testes , Tempo de Reação/fisiologia , Fases do Sono/fisiologia , Vigília/fisiologia
10.
IEEE Trans Biomed Eng ; 54(8): 1520-9, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17694874

RESUMO

Current demonstrations of brain-machine interfaces (BMIs) have shown the potential for controlling neuroprostheses under pure motion control. For interaction with objects, however, pure motion control lacks the information required for versatile manipulation. This paper investigates the idea of applying impedance control in a BMI system. An extraction algorithm incorporating a musculoskeletal arm model was developed for this purpose. The new algorithm, called the muscle activation method (MAM), was tested on cortical recordings from a behaving monkey. The MAM was found to predict motion parameters with as much accuracy as a linear filter. Furthermore, it successfully predicted limb interactions with novel force fields, which is a new and significant capability lacking in other algorithms.


Assuntos
Braço/fisiologia , Osso e Ossos/fisiologia , Encéfalo/fisiologia , Sistemas Homem-Máquina , Modelos Biológicos , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Simulação por Computador , Impedância Elétrica , Potenciais Evocados/fisiologia , Retroalimentação , Humanos , Interface Usuário-Computador
11.
IEEE Trans Biomed Eng ; 53(6): 1164-73, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16761843

RESUMO

Research on brain-machine interfaces (BMI's) is directed toward enabling paralyzed individuals to manipulate their environment through slave robots. Even for able-bodied individuals, using a robot to reach and grasp objects in unstructured environments can be a difficult telemanipulation task. Controlling the slave directly with neural signals instead of a hand-master adds further challenges, such as uncertainty about the intended trajectory coupled with a low update rate for the command signal. To address these challenges, a continuous shared control (CSC) paradigm is introduced for BMI where robot sensors produce reflex-like reactions to augment brain-controlled trajectories. To test the merits of this approach, CSC was implemented on a 3-degree-of-freedom robot with a gripper bearing three co-located range sensors. The robot was commanded to follow eighty-three reach-and-grasp trajectories estimated previously from the outputs of a population of neurons recorded from the brain of a monkey. Five different levels of sensor-based reflexes were tested. Weighting brain commands 70% and sensor commands 30% produced the best task performance, better than brain signals alone by more than seven-fold. Such a marked performance improvement in this test case suggests that some level of machine autonomy will be an important component of successful BMI systems in general.


Assuntos
Braço/fisiopatologia , Encéfalo/fisiologia , Transtornos dos Movimentos/reabilitação , Movimento , Robótica/métodos , Terapia Assistida por Computador/métodos , Interface Usuário-Computador , Eletroencefalografia/métodos , Potenciais Evocados/fisiologia , Retroalimentação , Força da Mão/fisiologia , Humanos , Imaginação/fisiologia , Robótica/instrumentação , Integração de Sistemas , Telemedicina/instrumentação , Telemedicina/métodos , Terapia Assistida por Computador/instrumentação
12.
Phys Med ; 32(1): 255-9, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26596874

RESUMO

There are many methods available to predict electron output factors; however, many centres still measure the factors for each irregular electron field. Creating an electron output factor prediction model that approaches measurement accuracy--but uses already available data and is simple to implement--would be advantageous in the clinical setting. This work presents an empirical spline model for output factor prediction that requires only the measured factors for arbitrary insert shapes. Equivalent ellipses of the insert shapes are determined and then parameterised by width and ratio of perimeter to area. This takes into account changes in lateral scatter, bremsstrahlung produced in the insert material, and scatter from the edge of the insert. Agreement between prediction and measurement for the 12 MeV validation data had an uncertainty of 0.4% (1SD). The maximum recorded deviation between measurement and prediction over the range of energies was 1.0%. The validation methodology showed that one may expect an approximate uncertainty of 0.5% (1SD) when as little as eight data points are used. The level of accuracy combined with the ease with which this model can be generated demonstrates its suitability for clinical use. Implementation of this method is freely available for download at https://github.com/SimonBiggs/electronfactors.


Assuntos
Elétrons , Neoplasias/radioterapia , Dosagem Radioterapêutica , Algoritmos , Humanos , Modelos Teóricos , Método de Monte Carlo , Distribuição Normal , Aceleradores de Partículas , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador , Reprodutibilidade dos Testes , Incerteza
13.
Sleep Med ; 25: 1-3, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27823701

RESUMO

BACKGROUND: Few studies have examined self-reported sleepwalking in older adolescents. The aim of this study was to examine the prevalence rates of sleepwalking in a one-month self-report period in Australian adolescents. METHODS: Participants were 532 Australian adolescents in their final two years of secondary school. RESULTS: The prevalence of sleepwalking in the one-month self-report period was 2.9% (95% confidence interval (CI) 1.47-4.33) in this sample-1% reported sleepwalking at least once a week in the previous month. A significant proportion (17.5%) of the participants was unsure if they had sleepwalked. CONCLUSION: The results provide data on the self-reported prevalence rate of sleepwalking in older adolescents. Compared with the population data, this rate falls within the confidence intervals of child and adult prevalence rates of sleepwalking and is consistent with a decline in sleepwalking from childhood and adulthood. Further research is needed to explore how adolescents know they sleepwalk to understand the reliability of self-report measures.


Assuntos
Autorrelato , Sonambulismo/epidemiologia , Adolescente , Austrália/epidemiologia , Criança , Feminino , Humanos , Masculino , Prevalência , Instituições Acadêmicas , Estudantes
14.
Gene ; 140(2): 203-9, 1994 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-8144028

RESUMO

Characterization of the human glucagon-receptor-encoding gene (GGR) should provide a greater understanding of blood glucose regulation and may reveal a genetic basis for the pathogenesis of diabetes. A cDNA encoding a complete functional human glucagon receptor (GGR) was isolated from a liver cDNA library by a combination of polymerase chain reaction and colony hybridization. The cDNA encodes a receptor protein with 80% identity to rat GGR that binds [125I]glucagon and transduces a signal leading to increases in the concentration of intracellular cyclic adenosine 3',5'-monophosphate. Southern blot analysis of human DNA reveals a hybridization pattern consistent with a single GGR locus. In situ hybridization to metaphase chromosome preparations maps the GGR locus to chromosome 17q25. Analysis of the genomic sequence shows that the coding region spans over 5.5 kb and is interrupted by 12 introns.


Assuntos
Cromossomos Humanos Par 17 , Receptores de Glucagon/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , DNA , DNA Complementar/genética , Glucagon/metabolismo , Humanos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Ratos , Receptores de Glucagon/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Transdução de Sinais
15.
Arch Ophthalmol ; 95(3): 474-8, 1977 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-843279

RESUMO

This is a clinicopathologic study of 18 oncocytic lesions involving the ocular adnexa. These lesions most commonly occur in elderly patients (median age 73), and there is a striking predilection for women. The broad spectrum of lesions included oncocytic adenomatous hyperplasia, oncocytomas, and oncocytic carcinoma. Ten lesions, all of which were oncocytomas, involved the caruncle, four the conjunctiva, and one the mucocutaneous junction of the eyelid. Two tumors involved the lacrimal sac and one the lacrimal gland. A review of the literature disclosed only 17 previously reported oncocytic lesions of the ocular adnexa. A small yellowish-tan or reddish caruncular mass, especially in an elderly woman, should alert the ophthalmologist to consider the possibility of oncocytoma in his differential diagnosis.


Assuntos
Adenoma/patologia , Túnica Conjuntiva/patologia , Neoplasias Oculares/patologia , Aparelho Lacrimal/patologia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
16.
Adv Colloid Interface Sci ; 103(3): 219-304, 2003 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-12781966

RESUMO

Until recently, the rapid time scales associated with the formation of an adsorbed surfactant layer at the solid-aqueous interface has prevented accurate investigation of adsorption kinetics. This has led to the mechanism of surfactant adsorption being inferred from thermodynamic data. These explanations have been further hampered by a poor knowledge of the equilibrium adsorbed surfactant morphology, with the structure often misinterpreted as simple monolayers or bilayers, rather than the discrete surface aggregates that are present in many surfactant-substrate systems. This review aims to link accepted equilibrium data with more recent kinetic and structural information in order to describe the adsorption process for ionic surfactants. Traditional equilibrium data, such as adsorption isotherms obtained from depletion approaches, and the most popular methods by which these data are interpreted are examined. This is followed by a description of the evidence for discrete aggregation on the substrate, and the morphology of these aggregates. Information gained using techniques such as atomic force microscopy, fluorescence quenching and neutron reflectivity is then reviewed. With this knowledge, the kinetic data obtained from relatively new techniques with high temporal resolution, such as ellipsometry and optical reflectometry, are examined. On this basis the likely mechanisms of adsorption are proposed.


Assuntos
Coloides/química , Soluções/química , Água/química , Adsorção , Calorimetria/métodos , Eletroquímica/métodos , Cinética , Espectroscopia de Ressonância Magnética/métodos , Microscopia de Força Atômica/métodos , Microscopia de Interferência/métodos , Espectrometria de Fluorescência/métodos , Eletricidade Estática , Propriedades de Superfície , Tensoativos/química , Agentes Molhantes/química
17.
J Antibiot (Tokyo) ; 49(10): 967-73, 1996 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-8968388

RESUMO

A novel inhibitor of platelet-activating factor (PAF) acetyltransferase, an essential enzyme in the remodeling pathway of platelet-activating factor synthesis, was identified by a high throughout screen of natural product extracts of microbial origin. The compound, ZG-1494 alpha, was isolated from an ethyl acetate extract of a culture broth of Penicillium rubrum through bioassay guided fractionation. The structure of ZG-1494 alpha was determined by spectroscopic methods. A key feature of the structure, which is relatively rare among natural products, is the 5-hydroxy-3-pyrrolin-2-one moiety. A 13C-13C INADEQUATE was utilized to unambiguously determine the regiochemistry of this molecule.


Assuntos
Acetiltransferases/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Penicillium/metabolismo , Animais , Inibidores Enzimáticos/química , Inibidores Enzimáticos/isolamento & purificação , Inibidores Enzimáticos/metabolismo , Células HL-60 , Histamina/metabolismo , Humanos , Estrutura Molecular , Fator de Ativação de Plaquetas/metabolismo , Ligação Proteica , Pirrolidinonas/química , Pirrolidinonas/isolamento & purificação , Pirrolidinonas/metabolismo , Pirrolidinonas/farmacologia , Coelhos , Receptores de Glucocorticoides/metabolismo
18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 64(1 Pt 2): 016413, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11461416

RESUMO

An annular shear cell has been used to investigate a number of factors known to influence stick-slip motion in an assembly of near monosized, spherical glass beads. In this paper, both the sample shear stress and volumetric strain were recorded, allowing new insights into the possible mechanics of stick-slip motion in a granular body. Rather than the commonly presented mechanism of sample dilation and fluidization accompanying the slip events, in the material studied here, sample dilation occurred during the preslip deformations of the granular body, while the slip event was accompanied by assembly contraction. Drive velocity and applied normal pressure were both found to influence the magnitude of the stick-slip spikes in a manner analogous to previous studies of stick-slip in assemblies of confined, near-spherical lubricant systems. Finally, atmospheric relative humidity was found to have a marked effect on the magnitude of the stick-slip motion. To investigate this mechanism more fully, the atomic force microscopy was employed to measure the particle-particle interaction forces as a function of atmospheric relative humidity. A water meniscus was found to form under all humidities, from less than 5% to greater than 95%. However, its influence on the adhesive forces varied by an order of magnitude. While most previous studies of stick-slip phenomena have attempted to remove atmospheric humidity as a variable, here we present a useful link between the role of relative humidity on particle-particle interaction forces and the macroscopic response of the granular assembly.

19.
J Pharm Pharmacol ; 34(5): 299-303, 1982 May.
Artigo em Inglês | MEDLINE | ID: mdl-6123567

RESUMO

The major urine metabolites of the neuroleptic drug, bromperidol, after oral doses to rats and dogs are p-fluorophenylacetic acid and its glycine conjugate resulting from oxidative N-dealkylation. While the same metabolites were also detected in human urine, also present was a major unknown component representing 50% of the total urine metabolites, which apparently was not formed by rats and dogs to any extent. Mass spectroscopic investigations a substituent attached to the tertiary hydroxyl group. The mass spectrum of the metabolite after trifluoroacetylation was consistent with an O-glucofuranosiduronolactone conjugate of bromperidol.


Assuntos
Haloperidol/análogos & derivados , Biotransformação , Fenômenos Químicos , Química , Cromatografia Líquida de Alta Pressão , Haloperidol/metabolismo , Humanos , Hidrólise , Espectrometria de Massas
20.
J Colloid Interface Sci ; 255(1): 91-7, 2002 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-12702372

RESUMO

Dilute aqueous dispersions of colloidal polystyrene latex spheres were flocculated by adding a nonadsorbing polymer sample, poly(acrylic acid). The structural compactness of the flocs thus formed was characterized in terms of their mass fractal dimension using the small-angle static light scattering technique. It was found that with low poly(acrylic acid) concentrations and thus weak depletion attraction forces, the dispersion medium viscosity had a marked effect on the floc structure. An increase in the viscosity led to formation of denser flocs. This was revealed in three sets of depletion flocculation experiments: (a) adjusting the background electrolyte concentration at a fixed level of poly(acrylic acid), (b) using water and 30% (w/w) glycerol as the respective solvents, and (c) inducing latex flocculation with two poly(acrylic acids) of different molecular weights at the respective critical polyacid concentrations. Direct force measurements were made with atomic force microscopy to isolate the influence of viscosity on floc structure from that of interparticle interaction energies. We conclude that the formation of denser flocs with increasing medium viscosity can be attributed to the reduced diffusivity of particles in the solution. The latter resulted in an enhanced rate of floc restructuring (through relaxation of attached particles) relative to floc growth.


Assuntos
Látex/química , Coloides , Cinética , Viscosidade , Água
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