Increased frequency of travel in the presence of cross-immunity may act to decrease the chance of a global pandemic.

The high frequency of modern travel has led to concerns about a devastating pandemic since a lethal pathogen strain could spread worldwide quickly. Many historical pandemics have arisen following pathogen evolution to a more virulent form. However, some pathogen strains invoke immune responses that provide partial cross-immunity against infection with related strains. Here, we consider a mathematical model of successive outbreaks of two strains-a low virulence (LV) strain outbreak followed by a high virulence (HV) strain outbreak. Under these circumstances, we investigate the impacts of varying travel rates and cross-immunity on the probability that a major epidemic of the HV strain occurs, and the size of that outbreak. Frequent travel between subpopulations can lead to widespread immunity to the HV strain, driven by exposure to the LV strain. As a result, major epidemics of the HV strain are less likely, and can potentially be smaller, with more connected subpopulations. Cross-immunity may be a factor contributing to the absence of a global pandemic as severe as the 1918 influenza pandemic in the century since. This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'. This issue is linked with the subsequent theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'.

Midpoint transverse process to pleura catheter placement for postoperative analgesia following video-assisted thoracoscopic surgery.

The ultrasound-guided midpoint transverse process to pleura block has been described as an alternative end-point for thoracic paravertebral blockade. Although originally described as a single-level block, midpoint transverse process to pleura blockade may cover more than one level when larger volumes of injectate are used. Moreover, a continuous catheter midpoint transverse process to pleura blockade technique was previously thought to be unfeasible. We report three cases where a midpoint transverse process to pleura continuous catheter technique was successfully used for postoperative analgesia following video-assisted thoracoscopic surgery.

Effects of racial socialization and racial identity on acculturative stress in African American college students.

The aim of this study was to determine if racial identity mediates the relation between racial socialization and acculturative stress in African American university students, once demographic factors are accounted for. In a sample of 84 participants, significant relations were found between racial socialization and acculturative stress, racial socialization and racial identity, and racial identity and acculturative stress. Partial support for a mediational model was found, with the best predictors of acculturative stress being immersion attitudes and internalization attitudes.

Establishment of normal values of nasal choanal size in children: comparison of nasal choanal size in children with and without symptoms of nasal obstruction.

Twenty-eight pediatric patients between the ages of 2 and 13 years underwent intraoperative measurement of the nasal choanae using an instrument custom designed for this purpose by the Pilling Surgical Instrument Company. Additional data points recorded included age, surgical procedure, and the presence or absence of nasal obstructive symptoms which was determined by carefully questioning parents or guardians. Results were analyzed using linear regression, analysis of variance, and logistic regression. Data supported the following conclusions: (1) a linear relationship exists between age and average choanal size with the choanae enlarging at a rate of 0.208 +/- 0.09 mm per year (P < 0.03, r2 = 0.16); (2) there is no significant difference between the average choanal size in children with and without nasal obstructive symptoms; (3) the size of the posterior choanal air space cannot be used to accurately predict the presence or absence of nasal obstructive symptoms in children between the ages of 2 and 13 years.

Reconstructive memory in the dating of personal and public news events.

Two experiments investigated memory for the dates of events selected and recorded by subjects in diaries. In Experiment 1, personal events and public news events were compared, with retention time varying from 1 week up to 9 months. It was found that the day of the week was more accurately identified for personal events than for news events, that day-of-the-week (DOW) accuracy did not decrease with increasing retention time, and that memory of the personal context of both event types was more important for DOW accuracy than was memory of the core of the events. These results support our view that memory of the day of the week is mainly reconstructed by reference to a temporal week schema based on personal experiences, and that the relation of news events to the week schema is mediated by memory of personal context. The distribution of DOW errors was modeled as the outcome of a process of guessing constrained by subdivisions of the week schema, without assuming any special temporal memory trace. In Experiment 2, the model was shown to fit independently collected data from a different subject pool and country equally well.

The use of partial temporal information in dating personal events.

The use of different types of partial temporal information is shown to affect dating accuracy and the distribution of errors in event dating. Several different types of partial temporal information are discussed, but three are highlighted by the data. Specifically, subjects' dating error patterns suggest that they (1) use different types of within-week information, (2) use recalled event sequences, and (3) use boundary landmarks to report the dates of events. In general, these data suggest that although precise temporal information is sometimes represented in the memory trace for an event, more often the date-related information is inferred from other aspects of memory.

The role of language familiarity in voice identification.

Four experiments examined the effects of language characteristics on voice identification. In Experiment 1, monolingual English listeners identified bilinguals' voices much better when they spoke English than when they spoke German. The opposite outcome was found in Experiment 2, in which the listeners were monolingual in German. In Experiment 3, monolingual English listeners also showed better voice identification when bilinguals spoke a familiar language (English) than when they spoke an unfamiliar one (Spanish). However, English-Spanish bilinguals hearing the same voices showed a different pattern, with the English-Spanish difference being statistically eliminated. Finally, Experiment 4 demonstrated that, for English-dominant listeners, voice recognition deteriorates systematically as the passage being spoken is made less similar to English by rearranging words, rearranging syllables, and reversing normal text. Taken together, the four experiments confirm that language familiarity plays an important role in voice identification.

The influence of uncoordinated histidines on iron release from transferrin. A chemical modification study.

Histidine residues that influence the chelate-mediated removal of iron from transferrin have been investigated. Diferric human serum transferrin was chemically modified to various extents using ethoxyformic anhydride, a reagent for histidines. A kinetic analysis of the modification reaction revealed the presence of a fast reacting pool of 9 +/- .8 histidine residues and a slow reacting pool of 5.8 +/- .6 residues. There are 18 histidine residues in transferrin. The rates of modification of the two pools differed by a factor of 5. The pyrophosphate-mediated removal of iron from the two binding sites of native and partially modified transferrins was studied at pH 6.9 using desferrioximine B as a terminal iron acceptor. Under these conditions, the rate of iron removal from the NH2-terminal site was about six times faster than from the COOH-terminal site. Both rates were significantly reduced, i.e. by a factor of approximately 6-8, upon complete ethoxyformylation of all reactive histidines on the protein. The kinetic data of partially modified transferrins were analyzed by the Tsou Chen-Lu statistical method; the results are consistent with the hypothesis that modification of a single uncoordinated histidine in each of the two iron binding domains stabilizes the protein kinetically against loss of iron. The dependence of the iron removal reaction on pH is consistent with such an interpretation. The putative histidines, although not ligands, may be close to the metal in both binding sites, thus influencing the rate of iron removal by pyrophosphate. These histidines belong to the pool of rapidly modified residues and thus are readily accessible to solvent and chelators.

The effects of salts and amino group modification on the iron binding domains of transferrin.

The origins of the effects of salts on the properties of the iron binding sites of transferrin have been investigated. The chaotropically distinct salts NaCl and NaClO4 each induce characteristic changes in the EPR lineshapes of the N- and C-terminal Fe3+ binding domains, respectively. To a good approximation the perturbed EPR spectrum of diferric transferrin in the presence of salts is the sum of the EPR spectra of the N- and C-terminal monoferric proteins. Acetylation of amino groups causes spectral and kinetic changes in the protein similar to those induced by NaClO4. Thus, both acetylation and NaClO4 cause a loss of structure in the g' = 4.3 EPR signal of the N-terminal domain, and both retard iron removal from this domain. In contrast, iron removal from the C-terminal domain is accelerated by acetylation or the presence of NaClO4. These observations are ascribed to charge effects of lysine residues which are probably in the vicinity of the iron binding sites.

Congenital cystic disease of the liver: isotope scanning, ultrasonography and angiography.

The radioisotope scanning, ultrasonic and angiographic findings in 16 patients with congenital cystic liver disease are described. Radioisotope scans are useful in determining the size, location and number of lesions. Ultrasonography is of value in differentiating solid from fluid-filled lesions, thus narrowing the differential diagnosis. At angiography, cysts produced well-defined avascular areas in the hepatogram in all 14 patients examined, enhanced by a well-defined "rim sign" in seven. This sign is considered pathognomonic of a cystic lesion (hydatid or congenital). Two had a "honeycomb" pattern at angiography, pathognomonic of congenital polycystic liver disease.

Encoding specificity: retrieval asymmetry in the recognition failure paradigm.

The paradigm producing recognition failure of recallable words was investigated in a series of three experiments. Results indicate that retrieval asymmetry: (a) exists in the recognition failure paradigm directly following list study, (b) increases significantly following a free-association task aimed at generation of the target words from the study list, and (c) can be used as a reasonably good predictor of the magnitude of recognition failure. Retrieval asymmetry and recognition failure are reliably related even when adjusted for the level of recognition probability, which has previously been shown by Tulving and Wiseman to be a good predictor of recognition failure.

The within-list distributed practice effect: Tests of the varied context and varied encoding hypotheses.

The present studies provided separate tests of the varied context and varied encoding hypotheses of the MP-DP effect. The investigation of varied encoding used an incidental learning procedure in which the nature of the orienting task was manipulated such that the subject attended to different attributes of words (varied encoding) or only one attribute (same encoding). While the prediction that the recall of MP-DP items should be comparable under comparable levels of encoding was not supported, differences were obtained in recall of items under same and variable orienting task conditions. An MP-DP effect was obtained under the incidental learning procedure. Tests of varied context involved the presentation of target items in list contexts which were the same or different from list contexts on previous occurrences of the item. The prediction that recall of items surrounded by different context should exceed that of items surrounded by the same context was not supported.