bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of virulence factors in the newly described Salmonella enterica serotype Keurmassar emerging in Senegal (sub-Saharan Africa)
Authors: GASSAMA-SOW A. , WANE A. A. , CANU N. A. , UZZAU S. , KANE A. AIDARA- , RUBINO S.
Published: January 2006

From 2000 to 2001, nine strains of Salmonella enterica belonging to the new serotype Keurmassar have been isolated from human and poultry samples at the Senegalese National Salmonella and Shigella Reference Laboratory at the Pasteur Institute, in Dakar. All strains carried virulence factors including Salmonella Pathogenicity Islands (SPI)-1, -2, -3 and -5 encoded genes. Strains did not harbour virulence plasmid. Ribotyping analysis revealed a single clone identical to Salmonella Decatur isolated in Zimbabwe. These data suggest that strains are closely related, and may have been spread clonally. In this new serotype, insertion sequence IS200 is not present.
Effectiveness of different policies in preventing meningococcal disease clusters following a single case in day-care and pre-school settings in Europe
Authors: BOCCIA D. , ANDREWS N. , SAMUELSSON S. , HEUBERGER S. , PERROCHEAU A. , STUART J. M.
Published: January 2006

National policies for chemoprophylaxis after single cases of meningococcal disease in day-care or nursery settings vary across Europe. We carried out a multi-national retrospective study to compare the effectiveness of different policies. Countries were divided into those recommending chemoprophylaxis only to close contacts (policy A, close) and those recommending chemoprophylaxis for all children in the same nursery (policy B, mass). Country-specific relative risk (RR) of a cluster was defined as the ratio of the number of clusters observed to the number of clusters expected by chance. In total, 37 clusters were identified between 1 January 1993 and 31 December 2002. After adjusting for marked heterogeneity in RR by country, the ratio of RR between countries suggested possible benefit from mass prophylaxis (RR ratio 3·8, 95% CI 0·7–22·0), although the difference was not statistically significant (P=0·22). The costs of this approach and the low risk of clustering need to be taken into account when deciding national policy.
Interpersonal Aspects of Responsibility and Obsessive Compulsive Symptoms
Authors: Ashbaugh Andrea R. , Gelfand Laurie A. , Radomsky Adam S.
Published: January 2006

Obsessive-compulsive disorder (OCD) is associated with an inflated sense of responsibility to prevent harm. Increasingly, it has been recognized that inflated responsibility is a complex phenomenon. The purpose of this study was to examine how interpersonal aspects of responsibility are related to symptoms of OCD. Three new valid and reliable scales assessing beliefs about other people's responsibility, comparative beliefs about responsibility, beliefs about the allocation of responsibility, and beliefs about how others allocate responsibility were used to evaluate interpersonal influences on responsibility. Whereas personal beliefs about responsibility were related to all OCD symptom types, it appears that beliefs about other people's responsibility were related to only a subgroup of symptom types. Furthermore, the belief that one is more responsible than others predicts OC symptoms beyond commonly assessed personal beliefs about responsibility. Finally, individuals with OC symptoms tend to allocate more responsibility to themselves than others, compared to individuals without OC symptoms, despite the fact that individuals with OC symptoms believe that others tend to allocate responsibility equitably. Results are discussed in terms of cognitive models of OCD.
Hemodynamic Impairment as a Stimulus for Functional Brain Reorganization
Authors: Marshall Randolph S , Krakauer John W , Matejovsky Theresa , Zarahn Eric , Barnes Anna , Lazar Ronald M , Hirsch Joy
Published: January 2006

We used functional magnetic resonance imaging to investigate whether hemispheral hemodynamic impairment can play an independent role in the functional reorganization of motor-related activity in the brain. Fourteen patients with large vessel occlusion but no infarct performed a simple motor task with the hand contralateral to the occluded vessel. Statistical parametric maps of regional activity were generated to compare the distribution of motor-related activity among patients with that of control subjects. Patients were classified into normal or abnormal cerebral hemodynamics on the basis of intracerebral vasomotor reactivity using transcranial Doppler and carbon dioxide inhalation. Controls and patients with normal vasomotor reactivity showed typical motor activity in contralateral motor areas. When the 9 patients with abnormal vasomotor reactivity were compared with the 14 control subjects in a single analysis, unique motor activation was identified in ipsilateral motor regions in the nonhypoperfused hemisphere. In a confirmatory analysis, blood oxygen level-dependent (BOLD) signal intensity was averaged in prespecified motor regions of interest. A significant group by hemisphere interaction was identified, driven by higher ipsilateral and lower contralateral hemisphere BOLD signal in patients with abnormal vasomotor reactivity compared with controls (F = 12.40, P=0.002). The average ipsilateral motor region signal intensity was also significantly higher in the subgroup of patients with abnormal vasoreactivity and no TIA compared with controls (P =0.04). Our results suggest that hemodynamic impairment in one hemisphere, even in the absence of any focal lesion or any symptoms can be associated with a functional reorganization to the opposite hemisphere.
Estradiol Reduces Activity of the Blood–Brain Barrier Na–K–Cl Cotransporter and Decreases Edema Formation in Permanent Middle Cerebral Artery Occlusion
Authors: O'Donnell Martha E , Lam Tina I , Tran Lien Q , Foroutan Shahin , Anderson Steven E
Published: January 2006

Estrogen has been shown to protect against stroke-induced brain damage, yet the mechanism is unknown. During the early hours of stroke, cerebral edema forms as increased transport of Na and Cl from blood into brain occurs across an intact blood–brain barrier (BBB). We showed previously that a luminal BBB Na–K–Cl cotransporter is stimulated by hypoxia and arginine vasopressin (AVP), factors present during cerebral ischemia, and that inhibition of the cotransporter by intravenous bumetanide greatly reduces edema in rats subjected to permanent middle cerebral artery occlusion (MCAO). The present study was conducted to determine whether estrogen protects in stroke at least in part by reducing activity of the BBB cotransporter, thereby decreasing edema formation. Ovariectomized rats were subjected to 210 mins of permanent MCAO after 7-day or 30-min pretreatment with 17 β-estradiol and then brain swelling and 2,3,5-triphenyltetrazolium chloride staining were assessed as measures of brain edema and lesion volume, respectively. Diffusion-weighed imaging was used to monitor permanent MCAO-induced decreases in apparent diffusion coefficient (ADC) values, an index of changes in brain water distribution and mobility. Na–K–Cl cotransporter activity of cerebral microvascular endothelial cells (CMECs) was assessed as bumetanide-sensitive K influx and cotransporter abundance by Western blot analysis after estradiol treatment. Estradiol significantly decreased brain swelling and lesion volume and attenuated the decrease in ADC values during permanent MCAO. Estradiol also abolished CMEC cotransporter stimulation by chemical hypoxia or AVP and decreased cotransporter abundance. These findings support the hypothesis that estrogen attenuates stimulation of BBB Na–K–Cl cotransporter activity, reducing edema formation during stroke.
Theoretical analysis of internal fluctuations and bistability in CO oxidation on nanoscale surfaces
Authors: Pineda M. , Imbihl R. , Schimansky-Geier L. , Zülicke Ch.
Published: January 2006

The bistable CO oxidation on a nanoscale surface is characterized by a limited number of reacting molecules on the catalytic area. Internal fluctuations due to finite-size effects are studied by the master equation with a Langmuir-Hinshelwood mechanism for CO oxidation. Analytical solutions can be found in a reduced one-component model after the adiabatic elimination of one variable which in our case is the oxygen coverage. It is shown that near the critical point, with decreasing surface area, one cannot distinguish between two macroscopically stable stationary states. This is a consequence of the large fluctuations in the coverage which occur on a fast time scale. Under these conditions, the transition times between the macroscopic states also are no longer separated from the short-time scale of the coverage fluctuations as is the case for large surface areas and far away from the critical point. The corresponding stationary solutions of the probability distribution and the mean first passage times calculated in the reduced model are supported by numerics of the full two-component model.
Large-volume ionization chamber with variable apertures for air-kerma measurements of low-energy radiation sources
Authors: Culberson W. S. , DeWerd L. A. , Anderson D. R. , Micka J. A.
Published: January 2006

This report describes the design and initial measurement results of a large-volume ionization chamber designed to realize the air kerma from therapeutic radiation sources emitting photons with energies up to about 70 keV. The measured ionization current is used to provide absolute source calibrations by the most widely used brachytherapy source strength metric called air-kerma strength. The variable-aperture free-air chamber (VAFAC), named because of its variable aperture stand, will provide insight into the angular dependence of air-kerma strength measurements. Another unique feature of this ionization chamber is its seed holder design that reduces unwanted scatter, ensures vertical positioning, and rotates the seed with a positional accuracy of 0.3°. Benchmark experiments show that the VAFAC agrees well with existing National Institute of Standards and Technology standards and is capable of measuring clinical-strength seeds with repeatabilities of less than 2% at the 1σ level (k=1).
High Q (33 000) all-epitaxial microcavity for quantum dot vertical-cavity surface-emitting lasers and quantum light sources
Authors: Muller Andreas , Shih Chih-Kang , Ahn Jaemin , Lu Dingyuan , Gazula Deepa , Deppe Dennis G.
Published: January 2006

Data are presented on the modal and lasing characteristics of a new type of vertical-cavity surface-emitting laser that uses an intracavity mesa to confine the optical mode, with the mesa also confining the quantum dot active region. The quantum dot active region is lithographically isolated within the intracavity mesa using etching and epitaxial regrowth to form an all-epitaxial microcavity light source. Cavity quality factors as high as 33 000 are measured, and ground state lasing is demonstrated with a single quantum dot active layer for temperatures up to ∼110K.
Highly directional stadium-shaped polymer microlasers
Authors: Lebental M. , Lauret J. S. , Hierle R. , Zyss J.
Published: January 2006

The far-field emission of two-dimensional stadium-shaped microlasers is investigated. Stadium-shaped microcavities based on a laser dye embedded in a polymer matrix have been elaborated. Such stadium-shaped microresonators, made by lithography and reactive ion etching have displayed quality factors greater than 6000 and a high output power. The highly directional far-field pattern of the emitted beam (full width at half maximum ∼15°) reflects the symmetries of the stadium shape.
Unbinding and preunbinding in surfactant solutions
Authors: Komura S. , Shimokawa N. , Kato T.
Published: January 2006

We propose models for the first-order unbinding transition of lyotropic lamellae in surfactant solutions. The coupling between the surfactant volume fraction and the elastic degree of freedom is considered so that the net attractive interaction between the surfactant molecules is enhanced. The elastic degree of freedom can be either (i) a membrane elastic degree of freedom or (ii) a bulk elastic degree of freedom. The phase behaviors of these two models are analyzed. For both cases, the unbinding transition becomes first order when the coupling is strong enough. We determine the associated preunbinding line which separates two lamellar phases having different repeat distances.
Polymer translocation through a nanopore: A two-dimensional Monte Carlo study
Authors: Luo Kaifu , Ala-Nissila T. , Ying See-Chen
Published: January 2006

We investigate the problem of polymer translocation through a nanopore in the absence of an external driving force. To this end, we use the two-dimensional fluctuating bond model with single-segment Monte Carlo moves. To overcome the entropic barrier without artificial restrictions, we consider a polymer which is initially placed in the middle of the pore and study the escape time τ required for the polymer to completely exit the pore on either end. We find numerically that τ scales with the chain length N as τ∼N1+2ν, where ν is the Flory exponent. This is the same scaling as predicted for the translocation time of a polymer which passes through the nanopore in one direction only. We examine the interplay between the pore length L and the radius of gyration Rg. For L⪡Rg, we numerically verify that asymptotically τ∼N1+2ν. For L⪢Rg, we find τ∼N. In addition, we numerically find the scaling function describing crossover between short and long pores. We also show that τ has a minimum as a function of L for longer chains when the radius of gyration along the pore direction R‖≈L. Finally, we demonstrate that the stiffness of the polymer does not change the scaling behavior of translocation dynamics for single-segment dynamics.
Xenon porometry at room temperature
Authors: Telkki Ville-Veikko , Lounila Juhani , Jokisaari Jukka
Published: January 2006

Xenon porometry is a method in which porous material is immersed in a medium and the properties of the material are studied by means of Xe129 nuclear magnetic resonance (NMR) of xenon gas dissolved in the medium. For instance, the chemical shift of a particular signal (referred to as signal D) arising from xenon inside small pockets formed in the pores during the freezing of the confined medium is highly sensitive to the pore size. In the present study, we show that when naphthalene is used as the medium the pore size distribution of the material can be determined by measuring a single one-dimensional spectrum near room temperature and converting the chemical shift scale of signal D to the pore radius scale by using an experimentally determined correlation. A model has been developed that explains the curious behavior of the chemical shift of signal D as a function of pore radius. The other signals of the spectra measured at different temperatures have also been identified, and the influence of xenon pressure on the spectra has been studied. For comparison, Xe129 NMR spectra of pure xenon gas adsorbed to porous materials have been measured and analyzed.
Electronic spectra and photodissociation of vinyl chloride: A symmetry-adapted cluster configuration interaction study
Authors: Arulmozhiraja Sundaram , Fukuda Ryoichi , Ehara Masahiro , Nakatsuji Hiroshi
Published: January 2006

The vertical absorption spectrum and photodissociation mechanism of vinyl chloride (VC) were studied by using symmetry-adapted cluster configuration interaction theory. The important vertical π→π* excitation was intensively examined with various basis sets up to aug-cc-pVTZ augmented with appropriate Rydberg functions. The excitation energy for π→π* transition obtained in the present study, 6.96eV, agrees well with the experimental value, 6.7–6.9eV. Calculated excitation energies along with the oscillator strengths clarify that the main excitation in VC is the π→π* excitation. Contrary to the earlier theoretical reports, the results obtained here support that the C–Cl bond dissociation takes place through the nCl-σC–Cl* state.
Single cylinder in situ scanning electron microscope fatigue system
Authors: Smiltneek Larry , Shinde Sachin R. , Hoeppner David W.
Published: January 2006

This article introduces a single cylinder fatigue machine adaptable to a scanning electron microscope chamber. The machine includes a node control mechanism to create a still observation node at any location on the specimen as fatigue cycling occurs, thereby allowing a point of interest to remain within view. The exceptional stability of this machine enables improved in situ study of the fatigue cracking phenomenon. For example, an in situ machine enhances the researcher’s ability to record material structural changes that precede crack nucleation and allows observation of the influences of microstructure (grain structure) on the early stages of crack propagation.
Microbubble oscillation in tubes with diameters of 12, 25, and 195 microns
Authors: Caskey Charles F. , Kruse Dustin E. , Dayton Paul A. , Kitano Tyler K. , Ferrara Katherine W.
Published: January 2006

Ultrasound contrast agents are often used to measure flow rate in the microvasculature; however, the oscillation of these agents in capillary-sized tubes has not been directly observed. Here, oscillations of microbubbles are examined in microvessel phantoms with diameters similar to those of capillaries. High-speed camera images demonstrate the effects of ultrasonic pressure and tube diameter and length on microbubble expansion and fragmentation occurrence. Microbubble displacement due to radiation force is also demonstrated in a phantom microvessel.
Elastic properties of MFe3N (M=Ni, Pd, Pt) studied by ab initio calculations
Authors: Music Denis , Schneider Jochen M.
Published: January 2006

Using ab initio calculations, we have studied the correlation between the electronic structure and elastic properties of MFe3N phases (M=Ni, Pd, Pt). These ternary nitrides possess a bulk-modulus-to-C44 ratio from 2.3 to 2.9, a rather unusual ratio for nitrides. This may be understood based on the electronic structure: Predominantly covalent-ionic Fe–N layers are interleaved with predominantly metallic Fe–M layers. We propose that the unusually large bulk-modulus-to-C44 ratio is a consequence of weak coupling between the Fe–N and Fe–M layers (giving rise to a low C44) as well as strong coupling within Fe–N layers (giving rise to a large bulk modulus).
Realization of high-energy density polycrystalline piezoelectric ceramics
Authors: Islam Rashed Adnan , Priya Shashank
Published: January 2006

This letter reports a high energy density piezoelectric material in the system given as: Pb[(Zr0.52Ti0.48)O3]1−x[(Zn1∕3Nb2∕3)O3]x+yMnCO3, where x=0.1 and y varies from 0.5to0.9wt%. A piezoelectric material with high energy density is characterized by a high product of piezoelectric voltage constant (g) and piezoelectric strain constant (d). The condition for obtaining large magnitude of g constant was derived to be as ∣d∣=εn, where ε is the permittivity of the material and n is constant having lower bound of 0.5. It was found that for all practical polycrystalline piezoelectric ceramic materials the magnitude of n lies in the range of 1.1–1.30 and as the magnitude of n decreases towards unity a giant enhancement in the magnitude of g was obtained. A two step sintering process was developed to optimize a polycrystalline ceramic composition with low magnitude of n. For the optimized composition the value of g33 and d33 was found to be 55.56×10−3m2∕C and 291×10−12C∕N, respectively, yielding the magnitude product d33∙g33 as ∼16168×10−15m2∕N which is significantly higher than the reported values in literature. The magnitude of n for this composition was calculated to be 1.151. This material is extremely promising for immediate applications in the sensing and energy harvesting.
ZnO p-n junction light-emitting diodes fabricated on sapphire substrates
Authors: Jiao S. J. , Zhang Z. Z. , Lu Y. M. , Shen D. Z. , Yao B. , Zhang J. Y. , Li B. H. , Zhao D. X. , Fan X. W. , Tang Z. K.
Published: January 2006

A ZnO p-n junction light-emitting diode (LED) was fabricated on a-plane Al2O3 substrate by plasma-assisted molecular-beam epitaxy. NO plasma activated by a radio frequency atomic source was used to grow the p-type ZnO layer of the LED. The current-voltage measurements at low temperatures showed a typical diode characteristic with a threshold voltage of about 4.0V under forward bias. With increasing temperature, the rectification characteristic was degraded gradually, and faded away at room temperature. Electroluminescence band of the ZnO p-n junction LED was located at the blue-violet region and was weakened significantly with increase of temperature. This thermal quenching of the electroluminescence was attributed to the degradation of the diode characteristic with temperature.
High-performance transparent flexible transistors using carbon nanotube films
Authors: Takenobu Taishi , Takahashi Tetsuo , Kanbara Takayoshi , Tsukagoshi Kazuhito , Aoyagi Yoshinobu , Iwasa Yoshihiro
Published: January 2006

Transparent flexible thin-film transistors (tf-TFTs) are an important focus of research since present silicon-based electronics cannot realize such devices. Here, we demonstrate a single-walled carbon nanotube (SWNT) tf-TFTs based on the solution process using transparent electrodes. SWNT tf-TFTs typically exhibit a mobility of 0.5cm2∕Vs and an on/off current ratio of ∼104. More importantly, these transistors are highly flexible and can be bent to a radius of 7.5mm without a significant loss in performance. This study therefore represents a major step towards “SWNT transparent plastic electronics.”
Temperature-dependent resistance changes in invar alloy nanocontact
Authors: Xu P. , Xia K. , Yang H. F. , Li J. J. , Gu C. Z.
Published: January 2006

A nanocontact structure of invar alloy is fabricated by using electron beam lithography and lift-off technique. The current-voltage (I-V) characteristic is measured under various temperatures from 10to300K. We find that the I-V curves are nonlinear and asymmetric, and the resistance change increases when the temperature decreases down to 50K. We attribute this effect to spin electron scattering by a domain wall trapped in the nanocontact. We also show that the anomaly is not observed in Cu nanocontacts. There is almost no resistance change in a Cu nanocontact with a change in the bias voltage.
An Information Statistical Approach to the Modifiable Areal Unit Problem in Incidence Rate Maps
Authors: Nakaya Tomoki
Published: January 2006

The modifiable areal unit problem becomes apparent when incidence rates are mapped on the basis of areal units. Although small units with high spatial accuracy can present unreliable rates, large spatial units may remove relevant geographical variation. Regarding mapping as a kind of statistical modelling, this author proposes a new methodology to select appropriate areal units using the Akaike information criterion and two search methods for an informative geographical aggregation in map construction. The optimal zoning of similarity is suitable for finding spatial anomalies but presents a biased overall pattern. An alternative approach is to cluster areal units according to explanatory variables: this shows clear spatial patterns of elderly men's mortality matching the ecological structure in the Tokyo metropolitan area.
Understanding Property Market Dynamics: Insights from Modelling the Supply-Side Adjustment Mechanism
Authors: Nanthakumaran Nanda , Watkins Craig , Orr Allison
Published: January 2006

The volatility of commercial property markets in the United Kingdom has stimulated the development of explanatory models of ‘price’ determination. These models have tended to focus on the demand-side as the driver of change. A corollary of this is that, despite the fact that construction lags are known to exacerbate cyclical fluctuations, the supply-side adjustment mechanism has been subject to relatively little research effort. In this paper the authors develop a new model of commercial property markets in the United Kingdom. The model is adapted from Poterba's two-equation asset-market approach to modelling the housing market. The first equation is an arbitrage relationship where the return on property is made up of rent, as determined in the user market for property services, and the capital gain, which is dependent on the return on alternative assets. This can be interpreted as a ‘stock’ demand equation. The second equation explains that ‘flow’ supply is determined by real capital values. The long-run empirical generalisation of the two-equation model allows the authors to estimate two key behavioural parameters required in explaining supply-side adjustment to market change. First, the authors interpret the coefficient on the capital value variable in the supply equation as an estimate of the long-run ‘price’ elasticity of supply. Second, from the demand equation, they estimate the extent to which new supply can act as an ‘automatic stabiliser’ on property values. It is argued that although increases in demand drive up property values, new development is also initiated and will, in turn, dampen down the growth in real capital values. The equations are estimated for the office, industrial, and retail sectors. Although there are no comparable estimates of supply elasticities in the real estate economics literature, the results are generally consistent with prior knowledge. Estimates of the stabiliser effect are also plausible and, taken together, the supply-side parameters help provide insights required in understanding property market dynamics in the last twenty-five years.
The Role of Contact Requirements in Producer Services Location
Authors: Goe W Richard , Lentnek Barry , MacPherson Alan , Phillips David
Published: January 2006

The authors explore the role of contact requirements in the locational tendencies of producer service establishments. Empirical evidence from two demand-side surveys suggests that close proximity between vendors and clients is required for contracts that involve frequent buyer–seller interaction (face-to-face linkages). These types of contracts are shown to be relatively low duration and/or low cost in nature. Specific activity classes that exhibit these characteristics include data processing, computer software development, product testing, and equipment repair services. In contrast, more advanced (and often more expensive) services such as management consulting and industrial design exhibit lower levels of contact sensitivity. The paper concludes with a discussion of forthcoming prospects for the development of a contact-based model of producer service location.
Privatisation and the Development of Tourism in the Czech Republic and Slovakia: Property Rights, Firm Performance, and Recombinant Property
Authors: Williams Allan M , Baláž Vladimir
Published: January 2006

Privatisation is one of the key elements of the package of neoliberal reforms in the transition economies of Central and Eastern Europe which collectively constitute the ‘sharp shock’ strategy. In this, privatisation is ascribed the role of redistributing and clarifying property rights, which is an assumed precondition for efficiency improvements in individual firms. In practice, the transformation is characterised by path dependency, cultural and political legacies, and uneven and partial reform of market institutions and of regulation. We contribute to the debate on the link between property rights and firm-level performance in three main ways. First, we analyse the tourism sector as a counterbalance to the emphasis in the existing literature on manufacturing and financial services; particular emphasis is given to the roles of ‘operators’ and the ‘nomenklatura’, and to complex, nonlinear shifts in property rights. Second, we assess the performance of tourism firms created by different forms of creative and distributive privatisation; this emphasises the diversity of property rights, market segmentation, and the capital and debt structures of firms. Third, the value of the concept of ‘recombinant’ property for analysing the complex and changing forms of property rights is critiqued. These arguments are illustrated through a case study of tourism in the Czech Republic and Slovakia.
The Web of Production: The Economic Geography of Commercial Internet Content Production in the United States
Authors: Zook Matthew A
Published: January 2006

This paper provides a description and analysis of the clustering behavior of the commercial Internet content industry in specific geographical locations within the United States. Using a data set of Internet domain name developed in the summer of 1998, I show that three regions—San Francisco, New York, and Los Angeles—are the leading centers for Internet content in the United States in terms both of absolute size and of degree of specialization. In order to understand better how the industrial structure of a region impacts the formation of the Internet content business, I provide an analysis of how the commercialization of the Internet has changed from 1993 to 1998 and explore the relationship between existing industrial sectors and the specialization in commercial domain names. Over time there appears to be a stronger connection between Internet content and information-intensive industries than between Internet content and the industries providing the computer and telecommunications technology necessary for the Internet to operate. Although it is not possible to assign a definitive causal explanation to the relationships outlined here, this paper provides a first step in theorizing about the overall commercialization process of the Internet.
On the Measurement and Generalisation of Urban Form
Authors: Longley Paul A , Mesev Victor
Published: January 2006

Developments in the provision and quality of digital data are opening up possibilities for more detailed measures of the form of urban areas. This paper begins with a review of some of the new data sources that are available in the United Kingdom, specifically the Ordnance Survey's ADDRESS-POINT product. The authors go on to develop a fine-scale data model of population densities, and fractal measures of the way in which urban development fills space. The research findings are compared with those of previous research that used less detailed data models.
Fathering and Faltering: “Sorry, but You Don't Have the Necessary Accoutrements”
Authors: Aitken Stuart C
Published: January 2006

The institution of the family is changing in complex and inscrutable ways. Ideally, it continues as a space of intimacy, love, and morality within which young children may find care and nurturing. This mythic conception of the institution belies the complex gendered realities of parenting. This paper focuses on the institution of fatherhood and the work of fathering. Much of our understanding of what it is to be a father hinges on an ‘idea’ that does not embrace the ‘fact’ of fathering as a daily emotional practice that is negotiated, contested and resisted differently in different spaces. Our enduring myths of social reproduction do not seem to support forms of masculinity that encompass a sense of self that is nurturing and domestically orientated. The paper derives from a series of discussions with new fathers and mothers in San Diego, California. I focus explicitly on constructions of fatherhood and the work of fathering with a focus on fathers who called themselves ‘househusbands’ and ‘Mr Moms’. Although many of the heterosexual parents in the San Diego study thought of motherhood and fatherhood as ‘natural’ categories that gave meaning to their emotions and behaviors, further scrutiny suggests that emotions and behaviors are complexly woven, unraveled and sometimes detached from the work of parenting. The paper's main contribution is to demonstrate that even the most active fathers tend to see their role as ‘helping out’ their partners rather than taking the main responsibility for child-care themselves.
Governing Interregional Conflicts: The Planning Approach to Managing Spillovers of Extended Metropolitan Pusan, Korea
Authors: Shin Dong-Ho
Published: January 2006

A perennial problem of urban industrial growth is spillovers into adjacent governmental jurisdictions. The resulting intergovernmental conflicts provide a window, as a part of urban governance, into conflict management. This paper focuses on such conflicts and the several ways of resolving them that have been attempted in southeastern Korea, centred on the country's major port of Pusan. In one way or another, conflicts with neighbouring Kyungnam Province have been festering since the administrative separation of Pusan as a metropolis, coequal in rank with the province of which it had been the capital. Three approaches of solving the region's problem were tried, all involving the central government in Seoul: aggressive annexations by Pusan of Kyungnam territories; a bland form of nonbinding mediation through an administrative device called ‘association’, and, most recently, a tripartite collaborative form of interregional planning involving Pusan, Kyungnam Province, and the national Ministry of Construction and Transportation. Based on enabling legislation, the collaborative planning approach appears to be working and has been adopted by a number of other conflicted regions in Korea.
E-Shopping in the Netherlands: Does Geography Matter?
Authors: Farag Sendy , Weltevreden Jesse , van Rietbergen Ton , Dijst Martin , van Oort Frank
Published: January 2006

Why consumers shop via the Internet, is a frequently asked question. As yet, the impact of spatial variables on e-shopping has received little attention. In this paper we report our investigation of the spatial distribution of Internet users and online buyers in the Netherlands for the time period 1996–2001 and the impact of spatial variables (residential environment and shop accessibility) on e-shopping. Two hypotheses are tested empirically. The first is that e-shopping is a predominantly urban phenomenon, because new technology usually starts in centres of innovation (innovation-diffusion hypothesis). The second is that people are more likely to adopt e-shopping when their accessibility to shops is relatively low (efficiency hypothesis). Our findings indicate that Internet use and online buying are still largely urban phenomena in the Netherlands, but that there is a trend towards diffusion to the weakly urbanised and rural areas. Not only the innovation diffusion hypothesis, but also the efficiency hypothesis is confirmed by our findings. People living in a (very) strongly urbanised area have a higher likelihood of buying online, but people with a low shop accessibility buy more often online. The analysis also shows that the support for the two hypotheses depends on the type of product. Airline tickets are still mainly bought in very strongly urbanised areas, whereas compact discs, videos, DVDs, and clothing are bought relatively more often in weakly urbanised areas. In conclusion, geography seems to matter for e-shopping.
Security and Space: Managing the Contradictions of Access Restriction in Johannesburg
Authors: Harrison Philip , Mabin Alan
Published: January 2006

Local officials attempt to resolve deep contradictions in most urban settings. The gating of sections of cities provides a notable example, setting fear of crime against rights of movement and access. Johannesburg, South Africa, reveals just such challenges. In this paper the authors review the recent history of policy formulation by city officials on ‘security access restriction’ in Johannesburg. They note the diverse and shifting views and behaviour of various actors and the difficulties faced by policymakers. They highlight how policy has emerged in a profoundly controversial and contested terrain, showing how Johannesburg, at least, has attempted to manage the conflicts. However, the policy environment remains unstable, and existing policy may be only a partial and temporary resolution to a deep contradiction.
Assessment of Urban Environmental Quality in a Subtropical City Using Multispectral Satellite Images
Authors: Nichol Janet , Wong Man Sing , Fung Christopher , Leung Kenneth K M
Published: January 2006

Urban environmental quality (UEQ) is a complex and spatially variable parameter of increasing concern, especially in densely populated cities of the tropics and subtropics where climate, air quality, and the urban infrastructure may interact to produce uncomfortable and hazardous effects. The study investigates the application of multispectral remote sensing from the Landsat ETM+ and IKONOS satellite sensors for the mapping of UEQ in urban Hong Kong at a detailed level, using the measurable, image-based parameters of temperature and biomass, and examines the relationship between these and air quality in selected study districts. Multiple-criteria queries on these two parameters show that spatial variations in UEQ are closely related to natural topographic factors and urban morphology. The amount of biomass, as opposed to total area of vegetation, is also shown to be an important factor in the spatial variation of UEQ. The data permit visualisation of the relationship between the human and natural factors involved in UEQ and generate recommendations for future planning and urban-renewal projects.
On the Algorithmic Design of Architectural Configurations
Authors: Fuhrmann Oded , Gotsman Craig
Published: January 2006

The algorithmic design of an architectural configuration depends on one's ability to compare the merit of different solutions quantitatively, in order to decide which design is superior. We propose a merit function that accounts for the amount of view from a given unit and its accessibility to other units. The amount of view is measured as the size of the spatial region visible from the center of the unit, and accessibility is quantified as the proximity of the unit to all other units in the configuration. We show how to compute the merit of a given configuration of units efficiently and to use this in an algorithm that generates configurations by greedily adding and removing units with the aim of maximizing the merit of the resulting configuration, either in a planar or a spatial setting. We demonstrate that this method reproduces familiar architectural designs (such as streets, plazas, and skylines) and sheds light on the forces that drive their creation.
A cold treatment for postharvest control of western flower thrips on strawberry runners
Authors: Williams P. , Green K. M. , Swanson B.
Published: January 2006

In 1998–99, outbreaks of Frankliniella occidentalis (Pergrande), western flower thrips (WFT), caused extensive damage to strawberry crops in the Yarra Valley, Victoria. These crops were within 30 km of Toolangi where over 80% of certified strawberry runners for Australia are produced. Commercial growers store runners for various periods of time at temperatures as low as –2°C. Cold temperature disinfestation was evaluated as a potential strategy in a contingency plan to prevent the spread of WFT on strawberry runners. Western flower thrips at various life stages on gerbera flowers (on which they were reared), were placed in small bags, made from the plastic liners used in commercial strawberry runner cartons, together with strawberry runners and exposed to –2°C for periods of 1, 2, 4, or 8 weeks. All WFT died within 4 weeks. Additional experiments were conducted in which WFT, in bags with runners or on gerbera leaf disks in petri dishes, were exposed to –2°C for 3 weeks. Only a few WFT survived these treatments; however, they were moribund. When they were assessed 2 days after completion of the exposure period, all WFT were dead. It was concluded that strawberry runners carrying WFT can be disinfested by exposing WFT to –2°C for 4 weeks and that this should be achievable under commercial conditions.
Reproductive protein protects functionally sterile honey bee workers from oxidative stress
Authors: Seehuus Siri-Christine , Norberg Kari , Gimsa Ulrike , Krekling Trygve , Amdam Gro V.
Published: January 2006

Research on aging shows that regulatory pathways of fertility and senescence are closely interlinked. However, evolutionary theories on social species propose that lifelong care for offspring can shape the course of senescence beyond the restricted context of reproductive capability. These observations suggest that control circuits of aging are remodeled in social organisms with continuing care for offspring. Here, we studied a circuit of aging in the honey bee (
Apis mellifera
). The bee is characterized by the presence of a long-lived reproductive queen caste and a shorter-lived caste of female workers that are life-long alloparental care givers. We focus on the role of the conserved yolk precursor gene
vitellogenin
that, in
Caenorhabditis elegans
, shortens lifespan as a downstream element of the insulin/insulin-like growth factor signaling cascade. Vitellogenin protein is synthesized at high levels in honey bee queens and is abundant in long-lived workers. We establish that
vitellogenin
gene activity protects worker bees from oxidative stress. Our finding suggests that one mechanistic explanation for patterns of longevity in bees is that a reproductive regulatory pathway has been remodeled to extend life. This perspective is of considerable relevance to research on longevity regulation that builds largely on inference from solitary model species.
Label-free detection of DNA hybridization using carbon nanotube network field-effect transistors
Authors: Star Alexander , Tu Eugene , Niemann Joseph , Gabriel Jean-Christophe P. , Joiner C. Steve , Valcke Christian
Published: January 2006

We report carbon nanotube network field-effect transistors (NTNFETs) that function as selective detectors of DNA immobilization and hybridization. NTNFETs with immobilized synthetic oligonucleotides have been shown to specifically recognize target DNA sequences, including H63D single-nucleotide polymorphism (SNP) discrimination in the
HFE
gene, responsible for hereditary hemochromatosis. The electronic responses of NTNFETs upon single-stranded DNA immobilization and subsequent DNA hybridization events were confirmed by using fluorescence-labeled oligonucleotides and then were further explored for label-free DNA detection at picomolar to micromolar concentrations. We have also observed a strong effect of DNA counterions on the electronic response, thus suggesting a charge-based mechanism of DNA detection using NTNFET devices. Implementation of label-free electronic detection assays using NTNFETs constitutes an important step toward low-cost, low-complexity, highly sensitive and accurate molecular diagnostics.
Postsynaptic TrkB signaling has distinct roles in spine maintenance in adult visual cortex and hippocampus
Authors: Chakravarthy Sridhara , Saiepour M. Hadi , Bence Matthew , Perry Sean , Hartman Robin , Couey Jonathan J. , Mansvelder Huibert D. , Levelt Christiaan N.
Published: January 2006

In adult primary visual cortex (V1), dendritic spines are more persistent than during development. Brain-derived neurotrophic factor (BDNF) increases synaptic strength, and its levels rise during cortical development. We therefore asked whether postsynaptic BDNF signaling through its receptor TrkB regulates spine persistence in adult V1. This question has been difficult to address because most methods used to alter TrkB signaling
in vivo
affect cortical development or cannot distinguish between pre- and postsynaptic mechanisms. We circumvented these problems by employing transgenic mice expressing a dominant negative TrkB–EGFP fusion protein in sparse pyramidal neurons of the adult neocortex and hippocampus, producing a Golgi-staining-like pattern. In adult V1, expression of dominant negative TrkB-EGFP resulted in reduced mushroom spine maintenance and synaptic efficacy, accompanied by an increase in long and thin spines and filopodia. In contrast, mushroom spine maintenance was unaffected in CA1, indicating that TrkB plays fundamentally different roles in structural plasticity in these brain areas.
Pollination decays in biodiversity hotspots
Authors: Vamosi Jana C. , Knight Tiffany M. , Steets Janette A. , Mazer Susan J. , Burd Martin , Ashman Tia-Lynn
Published: January 2006

As pollinators decline globally, competition for their services is expected to intensify, and this antagonism may be most severe where the number of plant species is the greatest. Using meta-analysis and comparative phylogenetic analysis, we provide a global-scale test of whether reproduction becomes more limited by pollen receipt (pollen limitation) as the number of coexisting plant species increases. As predicted, we find a significant positive relationship between pollen limitation and species richness. In addition, this pattern is particularly strong for species that are obligately outcrossing and for trees relative to herbs or shrubs. We suggest that plants occurring in species-rich communities may be more prone to pollen limitation because of interspecific competition for pollinators. As a consequence, plants in biodiversity hotspots may have a higher risk of extinction and/or experience increased selection pressure to specialize on certain pollinators or diversify into different phenological niches. The combination of higher pollen limitation and habitat destruction represents a dual risk to tropical plant species that has not been previously identified.
Stat5a/b are essential for normal lymphoid development and differentiation
Authors: Yao Zhengju , Cui Yongzhi , Watford Wendy T. , Bream Jay H. , Yamaoka Kunihiro , Hissong Bruce D. , Li Denise , Durum Scott K. , Jiang Qiong , Bhandoola Avinash , Hennighausen Lothar , O'Shea John J.
Published: January 2006

Cytokines that use the common gamma chain γc are critical for lymphoid development and function. Mutations of the IL-7 receptor, γc, or its associated kinase, Jak3, are the major cause of human severe combined immunodeficiency. Although activated by IL-7, Stat5a/b (Stat, signal transducer and activator of transcription) have been thought to play limited roles in lymphoid development. However, we now show that mice completely deficient in Stat5a/b have severely impaired lymphoid development and differentiation. Absence of Stat5 also abrogates T cell receptor γ rearrangement and survival of peripheral CD8
+
T cells. Thus, deficiency of Stat5 results in severe combined immunodeficiency, similar in many respects to deficiency of IL-7R, γc, and Jak3.
Activation of protein C by the thrombin–thrombomodulin complex: Cooperative roles of Arg-35 of thrombin and Arg-67 of protein C
Authors: Yang Likui , Manithody Chandrashekhara , Rezaie Alireza R.
Published: January 2006

The binding of Ca
2+
to the 70–80 loop of protein C inhibits protein C activation by thrombin in the absence of thrombomodulin (TM), but the metal ion is required for activation in the presence of TM. Structural data suggests that the 70–80 loop is located between two antiparallel β strands comprised of residues 64–69 and 81–91 on the protease domain of protein C. To test the hypothesis that a salt-bridge/hydrogen bond interaction between Arg-67 of the former strand and Asp-82 of the latter strand modulates the unique Ca
2+
-binding properties of protein C, we engineered a disulfide bond between the two strands by substituting both Arg-67 and Asp-82 with Cys residues. The activation of this mutant was enhanced 40- to 50-fold independent of TM and Ca
2+
. Furthermore, the Arg-67 to Ala mutant of protein C was activated in the absence of TM by the Arg-35 to Glu mutant of thrombin with the same efficiency as wild-type protein C by wild-type thrombin–TM complex. These results suggest that TM functions by alleviating the Ca
2+
-dependent inhibitory interactions of Arg-67 of protein C and Arg-35 of thrombin.