Further studies of the visually evoked subcortical potential in man

The Visually Evoked Subcortical Potential, a far-field signal, was originally defined to flash stimulation as a triphasic positive-negative-positive complex with mean latencies of P21 N26.2 P33.6 (Harding and Rubinstein 1980). Inconsistent with its subcortical source however, the signal was found to be tightly localised to the mastoid. This thesis re-examines the earlier protocols using flash stimulation and with auditory masking establishes by topographic studies that the VESP has a widespread scalp distribution, consistent with a far-field source of the signal, and is not a volume-conducted electroretinogram (ERG). Furthermore, mastoid localisation indicates auditory contamination from the click, on discharge of the photostimulator. The use of flash stimulation could not precisely identify the origin of the response. Possible sources of the VESP are the lateral geniculate body (LGB) and the superior colliculus. The LGB received 80% of the nerve fibres from the retina, and responds to high contrast achromatic stimulation in the form of drifting gratings of high spatial frequencies. At low spatial frequencies, it is more sensitive to colour. The superior colliculus is insensitive to colour and suppressed by contrast and responds to transitory rapid movements, and receives about 20% of the optic nerve fibres. A pattern VESP was obtained to black and white checks as a P23.5 N29.2 P34 complex in 93% of normal subjects at an optimal check size of 12'. It was also present as a P23.0 N28.29 P32.23 complex to red and green luminance balanced checks at 2o check size in 73% of subjects. These results were not volume-conducted pattern electroretinogram responses. These findings are consistent with the spatial frequency properties of the lateral geniculate body which is the considered source of the signal. With further work, the VESP may supplement electrodiagnosis of post-chiasmal lesions.

Executive function and emotional focus in autobiographical memory specificity in older adults

The current study examined the role of executive function in retrieval of specific autobiographical memories in older adults with regard to control of emotion during retrieval. Older and younger adults retrieved memories of specific events in response to emotionally positive, negative and neutral word cues. Contributions of inhibitory and updating elements of executive function to variance in autobiographical specificity were assessed to determine processes involved in the commonly found age-related reduction in specificity. A negative relationship between age and specificity was only found in retrieval to neutral cues. Alternative explanations of this age preservation of specificity of emotional recall are explored, within the context of control of emotion in the self-memory system and preserved emotional processing and positivity effect in older adults. The pattern of relationships suggests updating, rather than inhibition as the source of age-related reduction in specificity, but that emotional processing (particularly of positively valenced memories) is not influenced by age-related variance in executive control. The tendency of older adults to focus on positive material may thus act as a buffer against detrimental effects of reduced executive function capacity on autobiographical retrieval, representing a possible target for interventions to improve specificity of autobiographical memory retrieval in older adults.

Biofuel subsidies and international trade

This paper explores optimal biofuel subsidies in a general equilibrium trade model. The focus is on the production of biofuels such as corn-based ethanol, which diverts corn from use as food. In the small-country case, when the tax on crude is not available as a policy option, a second-best biofuel subsidy may or may not be positive. In the large-country case, the twin objectives of pollution reduction and terms-of-trade improvement justify a combination of crude tax and biofuel subsidy for the food exporter. Finally, we show that when both nations engage in biofuel policies, the terms-of-trade effects encourage the Nash equilibrium subsidy to be positive (negative) for the food exporting (importing) nation. © 2013 John Wiley & Sons Ltd.

The effects of ingroup-outgroup membership on minority influence when group membership is determined by a trivial categorisation

Two experiments are reported which investigate the influence of ingroup and outgroup minority influence where group membership was determined according to a trivial dimension. The results of the first experiment replicate an earlier study and show that an ingroup minority has significantly more influence than an outgroup minority. In the second study the connotations associated with membership of the ingroup and outgroup (positive/negative) were experimentally manipulated. When ingroup/outgroup membership was associated with a positive/negative image respectively, the ingroup minority had the most influence. However, when ingroup/outgroup membership was associated with a negative/positive image, as predicted, an outgroup minority had more influence than an ingroup minority. These results are interpreted as supporting an intergroup analysis of minority influence processes.

Help-seeking for medically unexplained hearing difficulties:a qualitative study

Aims - Up to 10% of audiology patients report diffi culties hearing speech in noise even though clinical investigation reveals normal hearing thresholds, in other words, no evidence of physical pathology. The diagnostic category applied to these patients is known as King-Kopetzky Syndrome (KKS). This study aimed to gather descriptions of patients' experiences of the clinical encounter involving their KKS diagnosis and analyse the themes of help-seeking, as part of a larger study into the process of coping with medically unexplained hearing diffi culties. Method - A qualitative approach was employed, comprising unstructured interviews in the homes of 25 patients who had attended audiology services (and received a diagnosis of KKS) in Bath and Cardiff. Thematic analysis of transcripts was undertaken, infl uenced by grounded theory techniques. Findings - Informants characterized the clinical encounter as either negative or positive. Negative consultations were those in which patients' illness claims were dismissed and as such not validated. Positive encounters were typifi ed by the provision of meaningful information that reconciled clinical information with the patients' experiences of hearing loss. Conclusion - Successful management of medically unexplained illnesses requires the adoption of a patient-centred approach, rather than focusing on the absence of observable pathology

In vitro activities of novel oxapenems, alone and in combination with ceftazidime, against gram-positive and gram-negative organisms

Four novel oxapenem compounds (i.e., AM-112, AM-113, AM-114, and AM-115) were investigated for their β-lactamase inhibitory activity against a panel of isolated class A, C, and D enzymes, which included expanded-spectrum β-lactamase enzymes (ESBLs). The oxapenems were potent β-lactamase inhibitors. Activity varied within the group, with AM-113 and AM-114 proving to be the most active compounds. The 50% inhibitory concentrations for these agents were up to 100,000-fold lower than that of clavulanic acid against class C and D enzymes. As a group, the oxapenems were more potent than clavulanic acid against enzymes from all classes. The ability of these compounds to protect ceftazidime from hydrolysis by β-lactamase-producing strains was evaluated by MIC tests that combined ceftazidime and each oxapenem in a 1:1 or 2:1 ratio. The oxapenems markedly reduced the MICs for ceftazidime against class C hyperproducing strains and strains producing TEM- and SHV-derived ESBLs. There was little difference between the activity of 1:1 and 2:1 combinations of ceftazidime and oxapenem. The oxapenems failed to enhance the activity of ceftazidime against derepressed AmpC-producing Pseudomonas aeruginosa strains.

A study of potential serum markers for a diagnosis of gram-positive and gram-negative bacterial sepsis

Sepsis continues to be a major cause of morbidity and mortality as it can readily lead tosevere sepsis, septic shock, multiple organ failure and death. The onset can be rapid and difficult to define clinically. Despite the numerous candidate markers proposed in the literature, to date a serum marker for sepsis has not been found. The aim of this study was to assay the serum of clinically diagnosed patients with eithera Gram-negative or Gram- positive bacterial sepsis for elevated levels of nine potentialmarkers of sepsis, using commercially produced enzyme linked immunosorbent assays(ELISA). The purpose was to find a test marker for sepsis that would be helpful toclinicians in cases of uncertain sepsis and consequently expose false positive BC'scaused by skin or environmental contaminants. Nine test markers were assayed including IL-6, IL-I 0, ILI2, TNF-α, lipopolysaccharide binding protein, procalcitonin, sE-selectin, sICAM -1 and a potential differential marker for Gram-positive sepsis- anti-lipid S antibody. A total of 445 patients were enrolled into this study from the Queen Elizabeth Hospital and Selly Oak Hospital (Birmingham). The results showed that all the markers were elevated in patients with sepsis and that patients with a Gram-negative sepsis consistently produced higher median/range serum levels than those with a Gram-positive sepsis. No single marker was able to identify all the septic patients. Combining two markers caused the sensitivities and specificities for a diagnosis of sepsis to increase to within a 90% to 100% range. By a process of elimination the markers that survived into the last phase were IL-6 with sICAM -1, and anti-lipid S IgG assays Defining cut-off levels for a diagnosis of sepsis became problematic and a semi-blind trial was devised to test the markers in the absence of both clinical details and positive blood cultures. Patients with pyrexia of unknown origin and negative BC were included in this phase (4). The results showed that IL-6 with sICAM-l are authentic markers of sepsis. There was 82% agreement between the test marker diagnosis and the clinical diagnosis for sepsis in patients with a Gram-positive BC and 78% agreement in cases of Gram-negative Be. In the PUO group the test markers identified 12 cases of sepsis and the clinical diagnosis 15. The markers were shown to differentiate between early sepsis and sepsis, inflammatory responses and infection. Anti-lipid S with IL-6 proved be a sensitive marker for Gram-positive infections/sepsis.

Brain connectivity in positive and negative syndrome schizophrenia

If, as is widely believed, schizophrenia is characterized by abnormalities of brain functional connectivity, then it seems reasonable to expect that different subtypes of schizophrenia could be discriminated in the same way. However, evidence for differences in functional connectivity between the subtypes of schizophrenia is largely lacking and, where it exists, it could be accounted for by clinical differences between the patients (e.g. medication) or by the limitations of the measures used. In this study, we measured EEG functional connectivity in unmedicated male patients diagnosed with either positive or negative syndrome schizophrenia and compared them with age and sex matched healthy controls. Using new methodology (Medkour et al., 2009) based on partial coherence, brain connectivity plots were constructed for positive and negative syndrome patients and controls. Reliable differences in the pattern of functional connectivity were found with both syndromes showing not only an absence of some of the connections that were seen in controls but also the presence of connections that the controls did not show. Comparing connectivity graphs using the Hamming distance, the negative-syndrome patients were found to be more distant from the controls than were the positive syndrome patients. Bootstrap distributions of these distances were created which showed a significant difference in the mean distances that was consistent with the observation that negative-syndrome diagnosis is associated with a more severe form of schizophrenia. We conclude that schizophrenia is characterized by widespread changes in functional connectivity with negative syndrome patients showing a more extreme pattern of abnormality than positive syndrome patients.

Du tout au rien:libre-choix et polarité negative

This monograph proposes a general model for the analysis of polysemy. The underspecified content of polysemic items produces interpretations in relation with characterised contextual indicators. This ternary set of schematic representations applies to the meaning organisation of French indefinite qui que ce soit ('any'). Universal positive readings, existential and opposition readings are generated by modalised predicate, a modalised proposition and syntactically adjoined functions. "Affective" contexts yield a negative polarity interpretation, the interpretation is generated through concessive reasoning, which explains how scalar values can be evoked by an item representing arbitrary selection. Such contextual reasoning and characterised contextual indicators are the two modes for the calculation of the contextual interpretation of polysemous items.

Negative data in DEA:a directional distance approach applied to bank branches

This paper is drawn from the use of data envelopment analysis (DEA) in helping a Portuguese bank to manage the performance of its branches. The bank wanted to set targets for the branches on such variables as growth in number of clients, growth in funds deposited and so on. Such variables can take positive and negative values but apart from some exceptions, traditional DEA models have hitherto been restricted to non-negative data. We report on the development of a model to handle unrestricted data in a DEA framework and illustrate the use of this model on data from the bank concerned.

Discovery of a potent phenolic N1-benzylidene- pyridinecarboxamidrazone selective against Gram-positive bacteria

As part of a study into antimycobacterial compounds a set of phenolic N1-benzylidene-pyridinecarboxamidrazones was prepared and evaluated. This report describes the unexpected discovery of a potent compound with a pronounced selectivity for Gram-positive bacteria over Gram-negative micro-organisms. In addition, this compound is active against various drug-resistant Gram-positive bacteria. © 2005 Elsevier Ltd. All rights reserved.

A DEA model for units with negative data

In this paper we propose an alternative method for measuring efficiency of Decision making Units, which allows the presence of variables with both negative and positive values. The model is applied to data on the notional effluent processing system to compare the results with recent developed methods; Modified Slacks Based Model as suggested by Sharp et al (2007) and Range Directional Measures developed by Silva Portela et al (2004). A further example explores advantages of using the new model.

A semi-oriented radial measure for measuring the efficiency of decision making units with negative data, using DEA

Data Envelopment Analysis (DEA) is a nonparametric method for measuring the efficiency of a set of decision making units such as firms or public sector agencies, first introduced into the operational research and management science literature by Charnes, Cooper, and Rhodes (CCR) [Charnes, A., Cooper, W.W., Rhodes, E., 1978. Measuring the efficiency of decision making units. European Journal of Operational Research 2, 429–444]. The original DEA models were applicable only to technologies characterized by positive inputs/outputs. In subsequent literature there have been various approaches to enable DEA to deal with negative data. In this paper, we propose a semi-oriented radial measure, which permits the presence of variables which can take both negative and positive values. The model is applied to data on a notional effluent processing system to compare the results with those yielded by two alternative methods for dealing with negative data in DEA: The modified slacks-based model suggested by Sharp et al. [Sharp, J.A., Liu, W.B., Meng, W., 2006. A modified slacks-based measure model for data envelopment analysis with ‘natural’ negative outputs and inputs. Journal of Operational Research Society 57 (11) 1–6] and the range directional model developed by Portela et al. [Portela, M.C.A.S., Thanassoulis, E., Simpson, G., 2004. A directional distance approach to deal with negative data in DEA: An application to bank branches. Journal of Operational Research Society 55 (10) 1111–1121]. A further example explores the advantages of using the new model.

Exchange rate economic exposure and hedging:the significance of currency options

This thesis focuses on the theoretical examination of the exchange rate economic (operating) exposure within the context of the theory of the firm, and proposes some hedging solutions using currency options. The examination of economic exposure is based on such parameters as firms' objectives, industry structure and production cost efficiency. In particular, it examines an hypothetical exporting firm with costs in domestic currency, which faces competition from foreign firms in overseas markets and has a market share expansion objective. Within this framework, the hypothesis is established that economic exposure, portrayed in a diagram connecting export prices and real exchange rates, is asymmetric (i.e. the negative effects depreciation are higher than the positive effects of a currency depreciation). In this case, export business can be seen as a real option, given by exporting firms to overseas customer. Different scenarios about the asymmetry hypothesis can be derived for different assumptions about the determinants of economic exposure. Having established the asymmetry hypothesis, the hedging against this exposure is analysed. The hypothesis is established, that a currency call option should be used in hedging against asymmetric economic exposure. Further, some advanced currency options stategies are discussed, and their use in hedging several scenarios of exposure is indicated, establishing the hypothesis that, the optimal options strategy is a function of the determinants of exposure. Some extensions on the theoretical analysis are examined. These include the hedging of multicurrency exposure using options, and the exposure of a purely domestic firm facing import competition. The empirical work addresses two issues: the empirical validity of the asymmetry hypothesis and the examination of the hedging effectiveness of currency options.