Functional integral bosonization for an impurity in a Luttinger liquid

We use a functional integral formalism developed earlier for the pure Luttinger liquid (LL) to find an exact representation for the electron Green function of the LL in the presence of a single backscattering impurity in the low-temperature limit. This allows us to reproduce results (well known from the bosonization techniques) for the suppression of the electron local density of states (LDOS) at the position of the impurity and for the Friedel oscillations at finite temperature. In addition, we have extracted from the exact representation an analytic dependence of LDOS on the distance from the impurity and shown how it crosses over to that for the pure LL.

Green's function for paraxial equation

The theory and experimental applications of optical Airy beams are in active development recently. The Airy beams are characterised by very special properties: they are non-diffractive and propagate along parabolic trajectories. Among the striking applications of the optical Airy beams are optical micro-manipulation implemented as the transport of small particles along the parabolic trajectory, Airy-Bessel linear light bullets, electron acceleration by the Airy beams, plasmonic energy routing. The detailed analysis of the mathematical aspects as well as physical interpretation of the electromagnetic Airy beams was done by considering the wave as a function of spatial coordinates only, related by the parabolic dependence between the transverse and the longitudinal coordinates. Their time dependence is assumed to be harmonic. Only a few papers consider a more general temporal dependence where such a relationship exists between the temporal and the spatial variables. This relationship is derived mostly by applying the Fourier transform to the expressions obtained for the harmonic time dependence or by a Fourier synthesis using the specific modulated spectrum near some central frequency. Spatial-temporal Airy pulses in the form of contour integrals is analysed near the caustic and the numerical solution of the nonlinear paraxial equation in time domain shows soliton shedding from the Airy pulse in Kerr medium. In this paper the explicitly time dependent solutions of the electromagnetic problem in the form of time-spatial pulses are derived in paraxial approximation through the Green's function for the paraxial equation. It is shown that a Gaussian and an Airy pulse can be obtained by applying the Green's function to a proper source current. We emphasize that the processes in time domain are directional, which leads to unexpected conclusions especially for the paraxial approximation.

Investigation of chromatic function in the normal and abnormal eye

This study examined the use of non-standard parameters to investigate the visual field, with particular reference to the detection of glaucomatous visual field loss. Evaluation of the new perimetric strategy for threshold estimation - FASTPAC, demonstrated a reduction in the examination time of normals compared to the standard strategy. Despite an increased within-test variability the FASTPAC strategy produced a similar mean sensitivity to the standard strategy, reducing the effects of patient fatigue. The new technique of Blue-Yellow perimetry was compared to White-White perimetry for the detection of glaucomatous field loss in OHT and POAG. Using a database of normal subjects, confidence limits for normality were constructed to account for the increased between-subject variability with increase in age and eccentricity and for the greater variability of the Blue-Yellow field compared to the White-White field. Effects of individual ocular media absorption had little effect on Blue-Yellow field variability. Total and pattern probability analysis revealed five of 27 OHTs to exhibit Blue-Yellow focal abnormalities; two of these patients subsequently developed White-White loss. Twelve of the 24 POAGs revealed wider and/or deeper Blue-Yellow loss compared with the White-White field. Blue-Yellow perimetry showed good sensitivity and specificity characteristics, however, lack of perimetric experience and the presence of cataract influenced the Blue-Yellow visual field and may confound the interpretation of Blue-Yellow visual field loss. Visual field indices demonstrated a moderate relationship to the structural parameters of the optic nerve head using scanning laser tomography. No abnormalities in Blue-Yellow or Red-Green colour CS was apparent for the OHT patients. A greater vulnerability of the SWS pathway in glaucoma was demonstrated using Blue-Yellow perimetry however predicting which patients may benefit from B-Y perimetric examination is difficult. Furthermore, cataract and the extent of the field loss may limit the extent to which the integrity of the SWS channels can be selectively examined.

Development of visual evoked responses to tritan,red-green and luminance stimuli in human infants

The principal aim of this work was to investigate the development of the S-cone colour-opponent pathway in human infants aged 4 weeks to 6 months. This was achieved by recording transient visual evoked responses to pattern-onset stimuli along a tritanopic confusion axis (tritan stimuli) at and around the adult isoluminant match. For comparison, visual evoked responses to red-green and luminance-modulated stimuli were recorded from the same infants at the same ages. Evoked responses were also recorded from colour-normal adults for comparison with those of the infants. The transient VEP allowed observation of response morphology as luminance differences were introduced to the chromatic stimuli. In this way, an estimate of isoluminance was possible in infants. Estimated isoluminant points for a group of six infants aged 6 to 10 weeks closely approximated the adult isoluminant match. This finding has implications for the use of photometric isoluminance in infant work, and suggests that photopic spectral sensitivity is similar in infants and adults. Abnormalities of the visual evoked responses to tritan, red-green and luminance-modulated stimuli in an infant with cystic fibrosis are reported. The results suggest abnormal function of the retino-striate visual pathway in this infant, and it is argued that these may be secondary to his illness, although data from more infants with cystic fibrosis are needed to clarify this further. A group of nine healthy infants demonstrated evoked responses to tritan stimuli by 4 to 10 weeks and to red-green stimuli by 6 to 11 weeks post-term age. Responses to luminance-modulated stimuli were present in all nine infants at the earliest age tested, namely 4 weeks post-term. The slightly earlier age of onset of evoked responses to tritan stimuli than for red-green may be explained by the relatively lower cone contrast afforded by red-green stimuli. Latency of the evoked response to both types of chromatic stimuli and to luminance-modulated stimuli decreased with age at a similar rate, suggesting that the visual pathways transmitting luminance and chromatic information mature at similar rates in young infants.

Green operations initiatives in the automotive industry:an environmental reports analysis and benchmarking study

Purpose: The purpose of this paper is to focus on investigating and benchmarking green operations initiatives in the automotive industry documented in the environmental reports of selected companies. The investigation roadmaps the main environmental initiatives taken by the world's three major car manufacturers and benchmarks them against each other. The categorisation of green operations initiatives that is provided in the paper can also help companies in other sectors to evaluate their green practices. Design/methodology/approach: The first part of the paper is based on existing literature on the topic of green and sustainable operations and the "unsustainable" context of automotive production. The second part relates to the roadmap and benchmarking of green operations initiatives based on an analysis of secondary data from the automotive industry. Findings: The findings show that the world's three major car manufacturers are pursuing various environmental initiatives involving the following green operations practices: green buildings, eco-design, green supply chains, green manufacturing, reverse logistics and innovation. Research limitations/implications: The limitations of this paper start from its selection of the companies, which was made using production volume and country of origin as the principal criteria. There is ample evidence that other, smaller, companies are pursuing more sophisticated and original environmental initiatives. Also, there might be a gap between what companies say they do in their environmental reports and what they actually do. Practical implications: This paper helps practitioners in the automotive industry to benchmark themselves against the major volume manufacturers in three different continents. Practitioners from other industries will also find it valuable to discover how the automotive industry is pursuing environmental initiatives beyond manufacturing, apart from the green operations practices covering broadly all the activities of operations function. Originality/value: The originality of the paper is in its up-to-date analysis of environmental reports of automotive companies. The paper offers value for researchers and practitioners due to its contribution to the green operations literature. For instance, the inclusion of green buildings as part of green operations practices has so far been neglected by most researchers and authors in the field of green and sustainable operations. © Emerald Group Publishing Limited.

Seventeen a-subunit isoforms of paramecium V-ATPase provide high specialization in localization and function

In the Paramecium tetraurelia genome, 17 genes encoding the 100-kDa-subunit (a-subunit) of the vacuolar-proton-ATPase were identified, representing by far the largest number of a-subunit genes encountered in any organism investigated so far. They group into nine clusters, eight pairs with >82% amino acid identity and one single gene. Green fluorescent protein-tagging of representatives of the nine clusters revealed highly specific targeting to at least seven different compartments, among them dense core secretory vesicles (trichocysts), the contractile vacuole complex, and phagosomes. RNA interference for two pairs confirmed their functional specialization in their target compartments: silencing of the trichocyst-specific form affected this secretory pathway, whereas silencing of the contractile vacuole complex-specific form altered organelle structure and functioning. The construction of chimeras between selected a-subunits surprisingly revealed the targeting signal to be located in the C terminus of the protein, in contrast with the N-terminal targeting signal of the a-subunit in yeast. Interestingly, some chimeras provoked deleterious effects, locally in their target compartment, or remotely, in the compartment whose specific a-subunit N terminus was used in the chimera.

Purchasing green transport and logistics services:implications for small business

Considering its strong environmental impact, logistics plays a critical role in green supply chain management. It provides strategic links in the supply chain and is an essential function in the delivery of green products to the consumer. There is a general consensus on the fact that more environmentally sustainable companies may be achieved only if transport and logistics activities also become greener. To achieve this objective, buyer companies need to incorporate green considerations in the purchasing of transport and logistics services. This appears particularly challenging for small and medium sized enterprises (SMEs) because of their traditional lack of managerial, organisational and financial resources that often result in failure to adopt an environmental perspective. In the extant literature, green purchasing has received increased attention over the past decade and the strategic importance of introducing green aspects into purchasing practices has been recognised. However, little has been written in relation to purchasing green transport and logistics services. The aim of this paper is to explore practices in the buying of green transport and logistics services and to derive implications for small buyer companies. The paper analyses how general environmental company ambitions and environmental purchasing practices are reflected when green transport and logistics services are purchased in three different European countries (Italy, Ireland and Sweden) using a multiple case study research approach. The results of the paper indicate that while the case companies show a relatively high concern for green issues at corporate level, a lower importance is attributed to green issues at the purchasing function level. When green concerns in the purchasing of transport and logistics services are analysed the level of importance decreases further. Thus, a conflicting attitude is evident between the overall corporate level and the purchasing of transport and logistics services specifically. This suggests that there is potential for improvement especially in the area of green collaboration in buyer and supplier relationships.

Weight loss strategies, stress, and cognitive function:supervised versus unsupervised dieting

The early stages of dieting to lose weight have been associated with neuro-psychological impairments. Previous work has not elucidated whether these impairments are a function solely of unsupported or supported dieting. Raised cortico-steroid levels have been implicated as a possible causal mechanism. Healthy, overweight, pre-menopausal women were randomised to one of three conditions in which they dieted either as part of a commercially available weight loss group, dieted without any group support or acted as non-dieting controls for 8 weeks. Testing occurred at baseline and at 1, 4 and 8 weeks post baseline. During each session, participants completed measures of simple reaction time, motor speed, vigilance, immediate verbal recall, visuo-spatial processing and (at Week 1 only) executive function. Cortisol levels were gathered at the beginning and 30 min into each test session, via saliva samples. Also, food intake was self-recorded prior to each session and fasting body weight and percentage body fat were measured at each session. Participants in the unsupported diet condition displayed poorer vigilance performance (p=0.001) and impaired executive planning function (p=0.013) (along with a marginally significant trend for poorer visual recall (p=0.089)) after 1 week of dieting. No such impairments were observed in the other two groups. In addition, the unsupported dieters experienced a significant rise in salivary cortisol levels after 1 week of dieting (p<0.001). Both dieting groups lost roughly the same amount of body mass (p=0.011) over the course of the 8 weeks of dieting, although only the unsupported dieters experienced a significant drop in percentage body fat over the course of dieting (p=0.016). The precise causal nature of the relationship between stress, cortisol, unsupported dieting and cognitive function is, however, uncertain and should be the focus of further research. © 2005 Elsevier Ltd. All rights reserved.

Nutritional influences on cognitive function:mechanisms of susceptibility

The impact of nutritional variation, within populations not overtly malnourished, on cognitive function and arousal is considered. The emphasis is on susceptibility to acute effects of meals and glucose loads, and chronic effects of dieting, on mental performance, and effects of cholesterol and vitamin levels on cognitive impairment. New developments in understanding dietary influences on neurohormonal systems, and their implications for cognition and affect, allow reinterpretation of both earlier and recent findings. Evidence for a detrimental effect of omitting a meal on cognitive performance remains equivocal: from the outset, idiosyncrasy has prevailed. Yet, for young and nutritionally vulnerable children, breakfast is more likely to benefit than hinder performance. For nutrient composition, despite inconsistencies, some cautious predictions can be made. Acutely, carbohydrate-rich–protein-poor meals can be sedating and anxiolytic; by comparison, protein-rich meals may be arousing, improving reaction time but also increasing unfocused vigilance. Fat-rich meals can lead to a decline in alertness, especially where they differ from habitual fat intake. These acute effects may vary with time of day and nutritional status. Chronically, protein-rich diets have been associated with decreased positive and increased negative affect relative to carbohydrate-rich diets. Probable mechanisms include diet-induced changes in monoamine, especially serotoninergic neurotransmitter activity, and functioning of the hypothalamic pituitary adrenal axis. Effects are interpreted in the context of individual traits and susceptibility to challenging, even stressful, tests of performance. Preoccupation with dieting may impair cognition by interfering with working memory capacity, independently of nutritional status. The change in cognitive performance after administration of glucose, and other foods, may depend on the level of sympathetic activation, glucocorticoid secretion, and pancreatic β-cell function, rather than simple fuelling of neural activity. Thus, outcomes can be predicted by vulnerability in coping with stressful challenges, interacting with nutritional history and neuroendocrine status. Functioning of such systems may be susceptible to dietary influences on neural membrane fluidity, and vitamin-dependent cerebrovascular health, with cognitive vulnerability increasing with age.

Novel glucagon-like peptide-1 (GLP-1) analog (Val8)GLP-1 results in significant improvements of glucose tolerance and pancreatic β-cell function after 3-week daily administration in obese diabetic (ob/ob) mice

This study evaluates the antidiabetic potential of an enzyme-resistant analog, (Val8)GLP-1. The effects of daily administration of a novel dipeptidyl peptidase IV-resistant glucagon-like peptide-1 (GLP-1) analog, (Val8)GLP-1, on glucose tolerance and pancreatic β-cell function were examined in obese-diabetic (ob/ob) mice. Acute intraperitoneal administration of (Val8)GLP-1 (6.25-25 nmol/kg) with glucose increased the insulin response and reduced the glycemic excursion in a dose-dependent manner. The effects of (Val8)GLP-1 were greater and longer lasting than native GLP-1. Once-daily subcutaneous administration of (Val8)GLP-1 (25 nmol/kg) for 21 days reduced plasma glucose concentrations, increased plasma insulin, and reduced body weight more than native GLP-1 without a significant change in daily food intake. Furthermore, (Val8)GLP-1 improved glucose tolerance, reduced the glycemic excursion after feeding, increased the plasma insulin response to glucose and feeding, and improved insulin sensitivity. These effects were consistently greater with (Val8)GLP-1 than with native GLP-1, and both peptides retained or increased their acute efficacy compared with initial administration. (Val8)GLP-1 treatment increased average islet area 1.2-fold without changing the number of islets, resulting in an increased number of larger islets. These data demonstrate that (Val8)GLP-1 is more effective and longer acting than native GLP-1 in obese-diabetic ob/ob mice.

Body iron is associated with cognitive executive planning function in college women

Evidence of the relationship between altered cognitive function and depleted Fe status is accumulating in women of reproductive age but the degree of Fe deficiency associated with negative neuropsychological outcomes needs to be delineated. Data are limited regarding this relationship in university women in whom optimal cognitive function is critical to academic success. The aim of the present study was to examine the relationship between body Fe, in the absence of Fe-deficiency anaemia, and neuropsychological function in young college women. Healthy, non-Anaemic undergraduate women (n 42) provided a blood sample and completed a standardised cognitive test battery consisting of one manual (Tower of London (TOL), a measure of central executive function) and five computerised (Bakan vigilance task, mental rotation, simple reaction time, immediate word recall and two-finger tapping) tasks. Women's body Fe ranged from - 4·2 to 8·1 mg/kg. General linear model ANOVA revealed a significant effect of body Fe on TOL planning time (P= 0.002). Spearman's correlation coefficients showed a significant inverse relationship between body Fe and TOL planning time for move categories 4 (r - 0.39, P= 0.01) and 5 (r - 0.47, P= 0.002). Performance on the computerised cognitive tasks was not affected by body Fe level. These findings suggest that Fe status in the absence of anaemia is positively associated with central executive function in otherwise healthy college women. Copyright © The Authors 2012.

Are dieting-related cognitive impairments a function of iron status?

The aim of the present study was to investigate whether the impairments in cognitive function observed in unsupported dieting are related to compromised Fe status. During a non-clinical intervention, overweight participants (age: 18-45 years, BMI: 25-30 kg/m2) either participated in a commercially available weight-loss regimen (n 14), dieted without support (n 17) or acted as a non-dieting control group (n 14) for a period of 8 weeks. Measurements of cognitive function and blood chemistry were taken at a pre-diet baseline, after 1 week and 8 weeks of dieting. After 1 week, unsupported dieters displayed impaired verbal memory, executive function and slower reaction speeds than the other two groups, this difference disappearing by the end of the study. There were no significant group-related changes in blood chemistry over the course of the study, although there were group-related changes in a number of self-reported food-related cognitions. In conclusion, impaired cognition among unsupported dieters is not due to compromised Fe status and is most likely to result from psychological variables. © 2012 The Authors.