1,673 research outputs found
Helping children think: Gaze aversion and teaching
No full textLooking away from an interlocutor's face during demanding cognitive activity can help adults answer challenging arithmetic and verbal-reasoning questions (Glenberg, Schroeder, & Robertson, 1998). However, such `gaze aversion' (GA) is poorly applied by 5-year-old school children (Doherty-Sneddon, Bruce, Bonner, Longbotham, & Doyle, 2002). In Experiment 1 we trained ten 5-year-old children to use GA while thinking about answers to questions. This trained group performed significantly better on challenging questions compared with 10 controls given no GA training. In Experiment 2 we found significant and monotonic age-related increments in spontaneous use of GA across three cohorts of ten 5-year-old school children (mean ages: 5;02, 5;06 and 5;08). Teaching and encouraging GA during challenging cognitive activity promises to be invaluable in promoting learning, particularly during early primary years
Wideband High Power Doherty Amplifiers
No full textCurrently the Doherty Power Amplifier (DPA) is replacing the traditional Class B amplifier in base-station and broadcast applications, as such becoming the preferred choice of industry due to its simplicity and high efficiency performance. In spite of its success, so far practical DPA implementations can provide only a very limited RF bandwidth, which tends to narrow down even more at higher power levels. This narrowband behavior of the DPA is mostly caused by the use of traditional operating classes for the active devices and bandwidth restrictions related to use of a conventional impedance inverter. In this work, the bandwidth of different DPA topologies has been analyzed, followed by a discussion of recent techniques that can help to improve the DPA bandwidth. To overcome the remaining bandwidth limitations in a DPA design, a novel differential configuration was proposed. In this approach, transmission line based baluns are used to implement the desired wideband 2nd harmonic terminations of the active devices. By combining this technique with a novel wideband impedance inverter, excellent DPA wideband performance can be achieved. Unfortunately, when going to practical balun implementations, various imperfections come to light, which trouble the achievable DPA bandwidth performance. For this reason, three practical balun structures are investigated in detail, namely, the coaxial cable based balun, the vertically installed planar balun and suspended planar stripline balun. To explore the proposed DPA concept when using practical baluns, two DPAs featuring mixed-signal driven inputs are presented. A dedicated design procedure for these DPAs is also given. The first prototype is implemented using NXP GaN devices and coaxial cable based baluns. Simulation results show a maximum output power of 52dBm, but in 6dB power back-off we only reach 40% efficiency from 530MHz to 700MHz, which is significantly less than the intend bandwidth (450MHz-810MHz). Using the lessons learned of this first amplifier, a second design with NXP LDMOS devices and suspended planar stripline balun has been developed. According to simulation this later design provides a maximum output power of 59dBm with the efficiency above 55% at both full power and 6dB power back-off. According the simulations this second design can even achieve 50% efficiency at 8dB back-off. The related center frequency is 650MHz with a high-efficiency bandwidth at 6dB power back-off (efficiency within 10% of its maximum) from 460MHz to 790MHz.Microwave groupMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Letter from A. J. Coleman, Montgomery, Alabama, to George D. Johnston, Tullahoma, Tennessee, November 18, 1862
No full textCherished Memories
No full textIssued as a blank book, with leaves of different hues. Contains manuscript passages and inscriptions signed by friends and family of Miss Teresa Doherty. Includes passages by Irish author, Mary Anne Sadlier. Includes plates engraved by W. E. Tucker, Thomas B. Welch, Elbridge Gerry Dunnel, and John Sartain; after works by William Radclyffe, Narcisse Virgile Diaz de la Peña, Frédéric Henri Schopin, and William Perring
The effectiveness of interventions to treat severe acute malnutrition in young children: a systematic review
No full textSevere acute malnutrition (SAM) arises as a consequence of a sudden period of food shortage and is associated with loss of a person’s body fat and wasting of their skeletal muscle. Many of those affected are already undernourished and are often susceptible to disease. Infants and young children are the most vulnerable as they require extra nutrition for growth and development, have comparatively limited energy reserves and depend on others. Undernutrition can have drastic and wide-ranging consequences for the child’s development and survival in the short and long term. Despite efforts made to treat SAM through different interventions and programmes, it continues to cause unacceptably high levels of mortality and morbidity. Uncertainty remains as to the most effective methods to treat severe acute malnutrition in young children.ObjectivesTo evaluate the effectiveness of interventions to treat infants and children aged < 5 years who have SAM.Data sourcesEight databases (MEDLINE, EMBASE, MEDLINE In-Process & Other Non-Indexed Citations, CAB Abstracts Ovid, Bioline, Centre for Reviews and Dissemination, EconLit EBSCO and The Cochrane Library) were searched to 2010. Bibliographies of included articles and grey literature sources were also searched. The project expert advisory group was asked to identify additional published and unpublished references.Review methodsPrior to the systematic review, a Delphi process involving international experts prioritised the research questions. Searches were conducted and two reviewers independently screened titles and abstracts for eligibility. Inclusion criteria were applied to the full texts of retrieved papers by one reviewer and checked independently by a second. Included studies were mapped to the research questions. Data extraction and quality assessment were undertaken by one reviewer and checked by a second reviewer. Differences in opinion were resolved through discussion at each stage. Studies were synthesised through a narrative review with tabulation of the results.ResultsA total of 8954 records were screened, 224 full-text articles were retrieved, and 74 articles (describing 68 studies) met the inclusion criteria and were mapped. No evidence focused on treatment of children with SAM who were human immunodeficiency virus sero-positive, and no good-quality or adequately reported studies assessed treatments for SAM among infants < 6 months old. One randomised controlled trial investigated fluid resuscitation solutions for shock, with none adequately treating shock. Children with acute diarrhoea benefited from the use of hypo-osmolar oral rehydration solution (H-ORS) compared with the standard World Health Organization-oral rehydration solution (WHO-ORS). WHO-ORS was not significantly different from rehydration solution for malnutrition (ReSoMal), but the safety of ReSoMal was uncertain. A rice-based ORS was more beneficial than glucose-based ORSs, and provision of zinc plus a WHO-ORS had a favourable impact on diarrhoea and need for ORS. Comparisons of different diets in children with persistent diarrhoea produced conflicting findings. For treating infection, comparison of amoxicillin with ceftriaxone during inpatient therapy, and routine provision of antibiotics for 7 days versus no antibiotics during outpatient therapy of uncomplicated SAM, found that neither had a significant effect on recovery at the end of follow-up. No evidence mapped to the next three questions on factors that affect sustainability of programmes, long-term survival and readmission rates, the clinical effectiveness of management strategies for treating children with comorbidities such as tuberculosis and Helicobacter pylori infection and the factors that limit the full implementation of treatment programmes. Comparison of treatment for SAM in different settings showed that children receiving inpatient care appear to do as well as those in ambulatory or home settings on anthropometric measures and response time to treatment. Longer-term follow-up showed limited differences between the different settings. The majority of evidence on methods for correcting micronutrient deficiencies considered zinc supplements; however, trials were heterogeneous and a firm conclusion about zinc was not reached. There was limited evidence on either supplementary potassium or nicotinic acid (each produced some benefits), and nucleotides (not associated with benefits). Evidence was identified for four of the five remaining questions, but not assessed because of resource limitation.LimitationsThe systematic review focused on key questions prioritised through a Delphi study and, as a consequence, did not encompass all elements in the management of SAM. In focusing on evidence from controlled studies with the most rigorous designs that were published in the English language, the systematic review may have excluded other forms of evidence. The systematic review identified several limitations in the evidence base for assessing the effectiveness of interventions for treating young children with severe acute malnutrition, including a lack of studies assessing the different interventions; limited details of study methods used; short follow-up post intervention or discharge; and heterogeneity in participants, interventions, settings, and outcome measures affecting generalisability.ConclusionsFor many of the most highly ranked questions evidence was lacking or inconclusive. More research is needed on a range of topic areas concerning the treatment of infants and children with SAM. Further research is required on most aspects of the management of SAM in children < 5 years, including intravenous resuscitation regimens for shock, management of subgroups (e.g. infants < 6 months old, infants and children with SAM who are human immunodeficiency virus sero-positive) and on the use of antibiotics.FundingThe National Institute for Health Research Technology Assessment programme.<br/
The induction of long-term plasticity of non-synaptic, synchronized activity by the activation of group I mGluRs
No full textIt is well established that activation of group I metabotropic glutamate receptors (mGluRs) produces long-lasting alterations in synaptic efficacy. We now demonstrate that activation of mGluRs can also induce long-term alterations in synchronised network activity that are both induced and expressed in the absence of chemical synaptic transmission. Specifically, in hippocampal slices in which synaptic transmission was eliminated by perfusing with a Ca 2+-free medium, the selective group I mGluR agonist 3,5-dihydroxyphenylglycine (DHPG) induced a persistent (>3 h) enhancement (>2-fold) of the frequency of synchronised bursting activity. The underlying biochemical mechanism responsible for the induction of this form of plasticity was similar to that for DHPG-induced long-term depression (LTD) in that it required the activation of tyrosine phosphatases. Also, like DHPG-induced LTD, this form of neuronal plasticity could be reversed by application of the mGluR antagonist α-methyl-4-carboxyphenylglycine (MCPG). This unusual form of plasticity, which presumably also occurs when synaptic transmission is intact, could contribute to long-term alterations in synchronised activity in hippocampal neuronal networks. © 2008 Elsevier Ltd. All rights reserved
The Governorship of Andrew Jackson
No full textIt was a stifling hot day in July of 1821 but the inhabitants of Pensacola, Florida, and hundreds of recently arrived newcomers were all jammed into the town’s central plaza. This was to be an important day in the lives of the people of Florida, for at ten o’clock in the morning the gaunt gray figure of Andrew Jackson would stalk from the governor’s residence and cross the plaza to the government house where the ceremonies marking the transfer of the Floridas from Spain to the United States would be completed. As he sat in the governor’s residence eating breakfast with his wife Rachel and the members of his staff, the old soldier may well have thought back to other days in Pensacola - for this was not the first time he had entered the ancient city. Twice in the previous seven years Jackson had led conquering armies into Spain’s feeble North American outpost. Yet each of those earlier visits had been followed by the restoration of Spanish sovereignty, and this time Jackson was present for the purpose of terminating that sovereignty
Volume 25, Number 1 - February 1947
No full textVolume 25, Number 1 – February 1947. 58 pages including covers and advertisements. Editorial Doherty, R.E. The Beast O\u27Brien, John J. On Coffee Eagle, George L. A Stranger in Strasbourg Shanley, Joseph V. Reflections Doherty, R.E. Thoughts on New York Gnys, Edward L. Chaos Morrison, Coleman On Floorwalkers Eagle, George L. Moment of Vision Deasy, John Living History Fortin, Andrew G. Effects of Studying the Essayists Critiqu
Andrew Jackson vs. the Spanish Governor
No full textFor more than one hundred years Andrew Jackson has been to writers of American history an exciting, inspiring, controversial, or shameful figure - according to the varying beliefs of those many writers. This writer, in recent issues of this Quarterly, has reexamined Jackson’s Florida career in two articles which were suggested by several previously unpublished Jackson letters. Several new letters coming to light have suggested a more detailed look at some of the ground covered in those earlier articles, specifically, the sources of hostility between Jackson and the last Spanish governor of West Florida, Jose Callava. Some historians have looked upon that hostility as stemming from Jackson’s inherent rascality; to others this was an inevitable product of his explosive temperament and frontier crudity. There is no denying the heat of his temper and its frequent manifestations, but this writer is inclined to deny that he was a rascal at heart or that he was the crude hillbilly some writers portray. Rather, let us dwell or the factors which conspired to inflame the feelings of both Jackson and Callava and brought on their collision, resulting in the throwing of the governor into the common jail at Pensacola at midnight under Jackson’s direct orders. These factors were: misunderstandings, several tedious delays, personal hardships, and cultural differences, as well as numerous petty annoyances
Wideband Doherty Power Amplifier Design for Base Station Application
No full textVanwege vertrouwelijke informatie of andere redenen is slechts een deel van de publicatie opgenomen in de repository. Due to confidential information or other reasons only a part of the publication is presented in the repository. Doherty Power Amplifier (DPA) is employed to improve the efficiency when operated with complex modulated signals. Due to its simplicity and high efficiency performance, it has become the preferred choice of industry. However, practical implementations of DPA only provide limited RF bandwidth, especially at high power level. The traditional narrow band device matching network, required phase shift for proper load modulation and impedance inverter seriously limit the bandwidth of DPA. In this work, the frequency behavior of the ideal 2-way symmetrical DPA is analyzed in detail, followed by the introduction of two new impedance inverters used to improve the bandwidth of DPA. In order to fully exploit the wideband potential of the new impedance inverters, the phase relation between the main and peak amplifier should be adjusted according to the power level at every frequency, which can be stored in a lookup table. Based on a previous wideband 20W DPA with mixed-signal input drive, in which the device output capacitance is incorporated into the impedance inverter, a modified DPA using the idea of compensated impedance inverter is designed and simulated. The prototype DPA design is implemented with NXP LDMOS bare die device. Simulation results have shown more than 50% 6dB back off efficiency from 1.5GHz to 2.2GHz, compared with the original case whose 50% efficiency bandwidth is from 1.9GHz to 2.3GHz. Since the prototype DPA is implemented at a low power level with bare die devices and mixed-signal input drive, it cannot be used for the practical base station applications. Traditional high power discrete DPA design method is introduced and the frequency behavior is analyzed. It is found that for the high power DPA, the matching network and the offset line are more important than the impedance inverter for the narrow bandwidth of DPA. A new DPA structure was proposed for wideband operation. Simulation results show smaller gain and power added efficiency spread in a 200MHz frequency band from 2.04GHz to 2.24GHz than the traditional DPA.Microwave groupMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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