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Notes: Scanning anode field emission microscopy is used to map the electron emission current I(x,y) under constant anode voltage and the electron extraction voltage V(x,y) under constant emission current as a function of tip position on carbon based thin film emitters. The spatially resolved field enhancement factor β(x,y) is derived from V(x,y) maps. It is shown that large variations in the emission site density (ESD) and current density can be explained in terms of the spatial variation of the field enhancement β(x,y). Comparison of β(x,y) and I(x,y) shows that electron emission currents are correlated to the presence of high aspect ratio field enhancing structures. We introduce the concept of field enhancement distribution f(β), which is derived from β(x,y) maps to characterize the field emission properties of thin films. In this context f(β)dβ gives the number of emitters on a unit surface with field enhancement factors in the interval (β,β+dβ). It is shown experimentally for the carbon thin film emitters investigated that f(β) has an exponential dependence with regard to the field enhancement factor β. The field enhancement distribution function f(β) can be said to give a complete characterization of the thin film field emission properties. As a consequence, the emitted current density and ESD can be optimized by tuning f(β) of the emitting thin film. © 2001 American Institute of Physics.

Notes: The effect of hypothermia upon cerebral metabolic rate for oxygen (CMRO2) was studied in artificially ventilated rats, anaesthetized with nitrous oxide. Cerebral blood flow was measured with a modification of the Kety and Schmidt technique using 133xenon. CMRO2, was found to decrease linearily with temperature in the temperature range 37°C-22°C. At normal temperatures CMRO2, fell by about 5 per cent per degree C. At a body temperature of 22°C both cerebral blood flow and CMRO2, were reduced to about 25 per cent of normal.

Notes: The current-induced emission degradation of a carbon nanotube (CNT) thin-film electron emitter is studied under constant emission current for different current levels, using a scanning anode field emission microscope. A permanent emission degradation is observed for emission currents higher than 300 nA per CNT and is associated with resistive heating at the CNT–substrate interface for the sample under investigation. A second field-induced emission degradation mechanism, associated with the removal of CNTs from the substrate, is also reported. © 2001 American Institute of Physics.

Notes: The investigation of the field emission (FE) properties of carbon nanotube (CNT) films by a scanning anode FE apparatus, reveals a strong dependence on the density and morphology of the CNT deposit. Large differences between the microscopic and macroscopic current and emission site densities are observed, and explained in terms of a variation of the field enhancement factor β. As a consequence, the emitted current density can be optimized by tuning the density of CNTs. Films with medium densities (on the order of 107 emitters/cm2, according to electrostatic calculations) show the highest emitted current densities. © 2000 American Institute of Physics.

Notes: Concerns about allergic side-effects of vaccines and about a possible promotion of allergic diseases contribute to incomplete vaccination rates in childhood. This article reviews the current understanding of these issues. There is evidence that pertussis and diphtheria/tetanus antigens elicit immunoglobulin E (IgE) antibody formation as part of the immune response. In murine models, pertussis toxin is an effective adjuvant for IgE formation against simultaneously administered antigens. In children, however, sensitization to unrelated antigens or development of allergic diseases do not seem to be augmented. In contrast, bacille Calmette–Guérin (BCG) and measles vaccination have been proposed as suppressors of allergy because of their T helper 1 (Th1)-fostering properties. In the murine system, BCG inhibits allergic sensitization and airway hyper-reactivity. Some epidemiological studies in humans suggest an inhibitory effect of tuberculosis on allergy. BCG vaccination in children, however, has no or merely a marginal suppressive effect on atopy. Other vaccine components such as egg proteins, gelatin, and antibiotics are a potential hazard to children with severe clinical reactions to these allergens. These rare children should be vaccinated under special precautions. In conclusion, vaccination programs do not explain the increasing prevalence of allergic diseases, but individual children may uncommonly develop an allergic reaction to a vaccine. The risks of not vaccinating children, however, far outweigh the risk for allergy. Therefore, childhood vaccination remains an essential part of child health programs and should not be withheld, even from children predisposed for allergy.

Notes: Background The prevalence of asthma and allergic diseases is significantly lower in post socialist Eastern Europe than in Western industrialized countries. The reason for this difference is largely unknown. Different types of childhood wheezing could be related to different risk factors.Objective To compare the prevalence of respiratory symptoms, asthma and atopic diseases among Estonian and Swedish schoolchildren and to evaluate characteristics for wheezing in the two countries.Methods In a prevalence study, population-based random samples of 10–11-year-old schoolchildren in Tallinn (n = 979), Estonia and in Linköping (n = 911) and Östersund (n = 1197), Sweden were studied by a parental questionnaire and skin prick tests (SPT). All 275 children with wheeze in the past 12 months and 710 randomly selected controls within the original cohorts were invited to a case-control study involving a parental questionnaire, examination for flexural dermatitis and bronchial challenge with hypertonic saline. The study adhered to the International Study of Asthma and Allergies in Childhood (ISAAC) Phase II protocol.Results The prevalence of current wheezing was similar (8–10%) in the three centres, while diagnosed asthma and atopic symptoms were more common in Sweden and cold-related respiratory symptoms were more prevalent in Estonia. Frequent wheezing was more common in Sweden than in Estonia (but significantly so only in Östersund). Wheezing children in Sweden had a high rate of positive SPT (49% in Linköping and 58% in Östersund) bronchial hyper-responsiveness (BHR) (48% in Linköping and Östersund) and anti-asthmatic treatment (63% in Linköping and 81% in Östersund). In Estonia, the proportion of wheezing children with positive SPT, BHR and anti-asthmatic treatment was only 26%, 13% and 17%, respectively. Domestic crowding was inversely related to wheezing in one of the study areas (Östersund). The mean baseline forced expiratory volume in one second (FEV1) was higher in Estonia than in Sweden, both in wheezing and non-wheezing children.Conclusions Our study suggested that although wheezing symptoms were equally common in Estonia and Sweden, they were less severe in Estonia. More frequent symptoms and a high rate of atopy, BHR and anti-asthmatic medication characterized wheezing children in Sweden. In contrast, BHR, atopy and medication were uncommon among wheezing children in Estonia.

Notes: Aims : To evaluate the role of antibiotic susceptibility for the treatment outcome of proton pump inhibitor-dependent and independent Helicobacter pylori eradication regimens.Methods : In a placebo-controlled clinical study of peptic ulcer patients with H. pylori infection, patients were randomized to receive lansoprazole, clarithromycin and tinidazole twice-daily, clarithromycin and tinidazole once-daily with lansoprazole or with placebo. Helicobacter pylori status was assessed by culture and antibiotic susceptibility by E-test minimal inhibitory concentration (MIC) in 205 clinical isolates.Results : Primary resistance to clarithromycin and metronidazole was 1 and 76%, respectively. In metronidazole susceptible strains eradication rates were similar at 〉 90% for all treatment groups (P = 0.49). With low-level metronidazole resistance (4 μg/mL 〈 MIC 〈 256 μg/mL), eradication rates were similar at 〉75% (P = 0.80). The major difference was found at high-level metronidazole resistance (MIC ≥ 256 μg/mL) with 95%, 58% and 21% eradication in the lansoprazole, clarithromycin and tinidazole twice-daily, lansoprazole, clarithromycin and tinidazole once-daily and placebo, clarithromycin and tinidazole once-daily groups, respectively (P 〈 0.001).Conclusion : In the absence of antibiotic resistance, a once-daily therapy of only clarithromycin and tinidazole can achieve a high rate of H. pylori eradication. Such a combination could offer a simpler and cheaper treatment option for developing countries. The standard, twice-daily proton pump inhibitor-based triple therapy was shown to be efficient in H. pylori eradication even in the presence of high-level metronidazole resistance.

Notes: Abstract Theγ-ray spectra following neutron capture in silicon have teen recorded in the neutron energy range 2.7–6.2 MeV and partial cross sections forγ-rays to the 2s1/2 ground state and 1d3/2 first excited states in29Si determined. The results indicate considerable fluctuations with neutron energy with a prominent resonance peak at 4.6 MeV in the (n,γ o) cross section. The existence of fluctuations is predicted in a recent theoretical calculation based on a model designed to include single-particle resonances in nuclear reaction processes.

Notes: Abstract The fine-structure splittings of the inverted 5 and 62 D states of potassium were measured by observing level-crossing signals at high magnetic fields. TheD levels were populated using step-wise excitations, employing two CW tunable dye lasers. For the fine-structure intervals δW we find: δW (5d)= −15,102.0 (5) MHz andδW(6d) = −7,965.8 (6) MHz. These values are about 100 times more accurate than previous results for these states. An expression is given, describing the fine-structure splittings in the sequence of potassium2D states.

Notes: Conclusions With some exaggeration it can be said that we now have at hand the necessary tools to analyse the sequence of events when a building is subjected to impact or impulsive loadings. The degree of precision in our analysis may be very poor, however, since we often do not know the relevant parameters well enough and, even if we did, the computation costs might be prohibitive. To obtain useful solutions for the practice much more research work is needed. To begin with one example, the damping effect of debris, floorings etc on top of an impacted floor slab has not been studied. Likewise, some highly non-linear phenomena, such as the crushing and cracking occurring in the contact zone at high impact velocities, are poorly understood. To proceed from there, little has been published on spalling from the surface opposite an impact, and only crude predictions of local penetration are possible. Some additional information may exist here in classified papers from defence research. Wave propagation in simple elastic media can be predicted but the presence of complex boundaries severely complicates the analysis and non-linearities in material behaviour and geometry further cut down the number of solvable cases. With the aid of numerical methods, primarily the finite element method, complex cases have been handled. The efforts of program location, data preparation, running costs, and data presentation are nevertheless considerable. For some situations such as designs against external and internal blasts, design formulas and diagrams already exist in the literature, though more detailed methods may be expected to emerge in these areas as well as in others in the future.