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This article discusses how detecting defects within reinforced concrete is vital to the safety and durability of infrastructure. A non-invasive technique, ElectroMagnetic Anomaly Detection (EMAD) is used in this article to provide information into the electromagnetic properties of reinforcing steel for which data analysis is currently performed visually. The first use of two neural network approaches to automate the analysis of this data is investigated in this article. These approaches are called Echo State Networks (ESNs) and Extreme Learning Machines (ELMs) where fast and efficient training procedures allow networks to be trained and evaluated in less time than traditional neural network approaches. Data collected from real-world concrete structures are analyzed in this article using these two approaches as well as using a simple threshold measure and a standard recurrent neural network. Two ESN architectures provided the best performance for a mesh-reinforced concrete structure, while the ELM approach offers a large improvement in the performance of a single tendon-reinforced structure.

X-radiography using the bremsstrahlung of a commercial broad spectrum X-ray source was used to quantify the differences and relationships between complex samples of unknown composition. The samples examined were painted and glazed ceramic mugs. The resulting pseudo-signatures were grey-level transmission spectra which can be usefully compared over a range of acceleration potential settings from 40 to 95 kV, taken at 1 kV intervals. These data are extracted from stacks of registered field-flattened X-ray images. It is shown that it is possible to differentiate between transmission spectra of the samples by concentrating mainly on the paint layers.

In this article, we report on the application of neural networks to the problem of making an element-specific determination of unknown metal targets based on the characteristics of their transmitted X-ray signatures. Our method was applied to two groups of metal targets that we characterised as light elements (atomic numbers between 40 and 50) and heavy elements (atomic numbers between 73 and 83). In all cases their X-ray signatures were pre-processed; randomly allocated into training and testing datasets; and then presented to a self-organising map neural network in order to perform the element-specific determination. The technique was able to make a correct determination of unknown metal targets with an accuracy of 95% for the heavy elements and 99% for the light elements.

This article reports on the employment of X-radiography using the bremsstrahlung of a commercial broad-.spectrum X-ray source to quantify the differences and relationships between complex materials of unknown composition. The materials examined were metallic powders embedded in a carrier paste. The resulting pseudo-signatures are transmission spectra over a range from 15 to 75 kV taken at I kV intervals, which were extracted from stacks of registered, field-flattened images. It is shown that it is possible to quantify differences between transmission spectra in order to differentiate between metallic powders used to impregnate the carrier paste.

The content of this article is indicated by what could be its full title: \An Expla- nation of the dependence of the rate of the cationic polymeriza- tions of alkenes and of the DP of their products, on the reaction variables, especially the size of the anionic moiety of the initia- tor." We continue here the dis- cussion started in 1965 and show mathematically how the theory of dieidic polymerizations by unpaired and paired cations can explain why some of these poly- merizations become faster with falling temperature, why the Arrhenius plot of the DP of the polymers obtained from most such systems shows a discontinu- ity or kink, and also how the tem- perature of minimum rate, TM, and that at which the kink occurs, TK, depend on the reaction varia- bles, namely the concentrations of monomer, m, and of initiator, c, and the a, D, and T (interionic distance in the ion-pair, dielectric constant of the reaction mixture and temperature). Our treatment explains why the most effective way of achieving the economi- cally desirable aim, to make the longest polymers at the highest possible temperatures, is by maxi- mizing the product a.D ,s o as to increase the TK, preferably by the use of polar solvents and initiators with large anions. The choice of such combinations by several investigators, but for other, vaguer, reasons, is given here a theoretical basis. Our argument is illustrated by Literature examples and is presented in the form of a new diagram (the Plesch-Austin plot) which shows the TK as a function of a.D for several

Homoclinic (and heteroclinic) trajectories are closed paths in phase space that connect one or more saddle points. They play an important role in the study of dynamical systems and are associated with the creation/destruction of limit cycles as a parameter is varied. Often, this creation/destruction process involves complicated sequences of bifurcations in small regions of parameter space and there is now an established theoretical framework for the study of such systems.The eigenvalues of saddle points in the phase space determine the behaviour of the system. In this article we present a new eigenvalue estimation technique based on a wavelet transformation of a time series under study and compare it with an existing method based on phase space reconstruction. We find that the two methods give good agreement with theory using clean model data, but where noisy data are analysed the wavelet technique is both more robust and easier to implement.

In this article element-specific mapping using a broad-spectrum laboratory based X-ray source is reported. Element-specific and element-exempt images of silver nitrate and di-hydrated barium chloride have been obtained from raw images collected either side of the K-edges for silver and barium. The informed positioning of filters between the source and sample narrowed the X-ray spectra, thereby enhancing the final images. For barium, samples with a barium area density of less than 8×10 −5 g mm −2 have been analysed. The system used here can be employed for mapping the distribution of elements from the middle of the second row transition metals to the light lanthanides.

The drying phase during the manufacture of ceramic pieces is often the point of failure owing to the formation of cracks. In this study, non-destructive microfocus X-ray imaging has been employed to study the onset of cracking in porcelain and correlate it with the moisture content. Samples of moist porcelain paste were extruded through dies of 30 and 50 mm diameter. Sections of the extrudate were placed into an X-ray transparent oven and imaged while drying at constant temperature and low humidity. The time to the onset of cracking was found to be a function of temperature. The mode of failure was consistent across the temperature range 40–120 °C. The higher the drying temperature, the shorter the time to failure and the higher the moisture loss at failure. For a particular paste consistency and sample geometry there was found to be a critical moisture content below which cracking began to occur. This moisture threshold was observed to be weakly temperature dependent; it appears to be more sensitive to sample geometry and paste consistency. A safe drying curve has been constructed which provides a boundary for the process parameters which prevent cracking. The implication is that during the drying of a ceramic piece, different sections may have different safe parameter boundaries and the process must be designed to keep all sections within the safe region.

A degassing procedure is necessary prior to taking ultrasonic measurements in aqueous kaolin suspensions as well as many other liquid based colloids. In this work we compare two degassing methods and show that subjecting a sample to a power ultrasound field is easier and less time consuming than exposing it to a vacuum. We also combine degassing and deflocculation procedures to show that air bubbles are trapped in cage-like kaolin flocs and are released when such flocs break up.

Early theories of acoustic propagation such as those by Urick, and Urick and Ament, are attractive because of their computational simplicity, but limited in application. The more complex models of Allegra and Hawley, and Harker and Temple, have since gained application. A wideband ultrasonic attenuation and phase velocity spectrometer have been used to determine the validity of these models for a range of colloidal materials. Measurements taken validate the Allegra and Hawley model for colloids with spherical base particles. The Harker and Temple model is used to infer changes in the flocculation state of kaolin slurries which result from chemical intervention.

Sections 36–41 of the Violent Crimes Reduction Act (2006), which came into force in England and Wales on 1st October 2007, have placed significant restrictions on the sale and possession of ‘realistic imitation firearms’. This legislation attempts to produce a definition of a ‘realistic imitation’ which clearly differentiates these items from other imitation firearms (which are not covered by the legislation). This paper will go a stage further by demonstrating techniques by which blank firing realistic imitation firearms which may be suitable for illegal conversion to fire live rounds may be differentiated from other less ‘suitable’ (but visually identical) realistic imitations. The article reports on the use of X-radiography, utilizing the bremsstrahlung of a commercial broad spectrum X-ray source, to identify the differences between alloys constituting the barrels of distinct replica and/or blank firing handguns. The resulting pseudo-signatures are transmission spectra over a range from 20 to 75 kV, taken at 1 kV intervals, which are extracted from stacks of registered, field flattened images. It is shown that it is possible to quantify differences between transmission spectra for components of different realistic imitation fire arms, and apply the results to determine the suitability of particular gun barrels from blank firing imitation firearms for illegal conversion to fire live rounds, or related illegal modifications.

This paper investigates the method for object fingerprinting in the context of element specific x-ray imaging. In particular, the use of spectral descriptors that are illumination invariant and viewpoint independent for pattern identification was examined in some detail. To improve generating the relevant "signature", the spectral descriptor constructed is enhanced with a differentiator which has built-in noise filtration capability and good localisation properties, thus facilitating the extraction of element specific features at a coarse-grained level. In addition to the demonstrable efficacy in identifying significant image intensity transitions that are associated with the underlying physical process of interest, the method has the distinct advantage of being conceptually simple and computationally efficient. These latter properties allow the descriptor to be further utilised by an intelligent system capable of performing a fine-grained analysis of the extracted pattern signatures. The performance of the spectral descriptor has been studied in terms of the quality of the signature vectors that it generated, quantitatively based on the established framework of Spectral Information Measure (SIM). Early results suggested that such a multiscale approach of image sequence analysis offers a considerable potential for real-time applications.

Jonathan Osborne's letter (February p20) in response to Joao Magueijo's article on university-lecturer training (December 2009 pp16–17) surely cannot go unanswered. Contrary to what Osborne claims, Magueijo did not say that we should use lectures because students like them – in fact, he advocated the use of exactly the "interactive, discursive methods" that Osborne favours as alternatives to traditional lecture courses. The real point of Magueijo's article was that lecturer training as currently practised in the UK is a waste of time – not that lecturers need no training at all.

Thefractal dimension of kaolin flocs suspended in water was increased by the addition of potassium chloride and indirectly monitored by low-power ultrasonic pulses in a test cell with a "pitch-catch" configuration. The results from these measurements were compared with fractal dimensions obtained from quasi-elastic light-scattering measurements in a kaolin suspension of a much lower solid volume fraction. Further comparison with a coupled phase theory of ultrasound propagation, utilizing measured slope viscosity and particle size distribution, revealed that the observed changes in the ultrasound signature were commensurate with changes in the fractal dimension observed by light scattering over a potassium chloride concentration range of approximately 0-1 mM. Copyright 1999 Academic Press.

"There is strong evidence for the cancerous impact of cigarette smoking, but we should not ignore those who think otherwise." Imagine the outcry if these words were to open an editorial in the flagship magazine of a leading medical society. Yet change "cancerous impact of cigarette smoking" to "human impact on climate change" and you obtain the opening sentence of the Physics World editorial in the February issue (p15). You might think I am stretching the point, but the tide of expert opinion really is as strong for human-induced climate change as it is for cigarette-induced cancer.

By employing a simplified technique of autocerebral hypothermic perfusion (without pump or oxygenator) the monkey brain has been cooled to intracerebral temperatures 5–8°C and rendered ischaemic for 1 h with normal recovery in the animals. The efficiency of isolated cerebral cooling was markedly enhanced with exogenous catecholamines and a cephalic ice helmet.

Cerebral viability (as evidenced by the persistence of EEG activity) has been maintained in situ for many hours by utilizing simplified extracorporeal (pump-oxygenator) perfusion systems to provide cephalo-cerebral circulation, in cardiac-arrested canine and monkey preparations. Additional studies using unicarotid mechanical perfusion and EEG monitoring demonstrated the limitations at present characterizing the pumping elements utilized in isolated cerebral perfusion.

James C. Austin and Donald A. Koch's Popular Literature in America (Bowling Green, Ohio: Bowling Green University Popular Press, 1972—$17.95/3.00) John Fischer's Six in the Easy Chair (Urbana: University of Illinois Press, 1973—$7.95) Fredric [sic] Wertham's The World of Fanzines: A Special; Form of Communication (Carbondale: Southern Illinois University Press, 1973—$10.00) Arthur Asa Berger's The Comic Stripped American (New York: Walker, 1973—$7.95) Mass Comm Review (Department of Journalism, Temple University, Philadelphia, Pa. 19122—$4.00 per year for two issues) Marvin Kimbrough's Black Magazines: An Exploratory Study (Austin: Center for Communication Research of the University of Texas, 1973—$2.00, paper) George R. Allen's The Graduate Students' Guide to Theses and Dissertations: A Practical Manual for Writing and Research (San Francisco: Jossey-Bass, 1973—$7.75)

The ultrasonic Doppler flow meter was used to measure digital blood velocity in two groups of ten male volunteers. In the experimental group, digital blood-flow velocity was measured before and after smoking one cigarette. In the control group, two digital blood-flow velocity measurements were made at the same intervals. Blood-flow velocity remained unchanged in the control group. In the experimental group the Doppler shift was reduced by 40±9% during systole, 48±10% during diastole, and the mean Doppler shift was reduced by 42±6% Since the Doppler shift is proportional to blood-flow velocity, it is concluded that smoking a single cigarette reduces mean blood-flow velocity by 42±6% ( JAMA 229:1327-1328, 1974)

T HE LETTERS OF BILL ARP, by the Georgia humorist Charles Henry Smith, have been recognized as an appealing expression of the Southern point of view during the Civil War, the Reconstruction, and the later nineteenth century. They also have been noted as a source of authentic language and lore from northwestern Georgia. The following list grew out of the preparation of James C. Austin's Bill Arp (New York: Twayne, 1970). Smith was the son of a New England merchant who moved to Georgia about 1817. Born in 1826 in Lawrenceville, Smith later moved to Rome and then to Cartersville. Until his death in 1903, he was a resident of north Georgia, having left the region only for occasional trips for pleasure or for lecturing or because of military duties or the necessity of moving his family during the Civil War. He attended Franklin College (later the University of Georgia) in Athens for almost four years, and in 1850 he was admitted to the Georgia bar. As a circuit lawyer, he swapped stories and witticisms with all classes. After service in the Confederate Army, he spent the remainder of his long life as successively a merchant, a politician, a farmer, and a writer. The Bill Arp letters, begun during the heat of secession in 1861, had tremendous local popularity. Published in the Rome Courier and other Southern papers, and as far away as the New York Metropolitan Record and the Detroit Free Press, they helped Southern morale and expressed Southern viewpoints. From 1878 to 1903, they appeared regularly in the Atlanta Constitution as the genial philosophizing of an old-fashioned farmer. The object of the list that follows is to present a sampling of the linguistic features of the Bill Arp letters. The sampling is intended as a representative cross section of the complete Bill Arp letters as published in book form. Because much of the deliberate misspelling and dialect spelling was eliminated in the book publications, one of the letters as it originally appeared in the Atlanta Southern Confederacy in 1863 has been included as a source. The citations in the list are selected from a word-by-word consideration of all recognizable deviations from standard English in that letter and in about twenty pages from each of the five books listed below, plus random selections from many more pages. The twenty-page portions were chosen to represent the chronological changes that occurred in the writing, the differences due to different media of publication, and the obvious fluctuation of the literary