bluuebunny/crossref_metadata_2025 huggingface dataset:
Forest Management, Conservation, and Global Timber Markets
Authors: Sohngen Brent , Mendelsohn Robert , Sedjo Roger
Published: July 2006

This article develops a global timber market model which captures how timber supply reacts to future predicted increases in the demand for timber. Higher future demand is expected to increase prices, increase investments in regeneration, increase establishment of plantations, and expand output. Dynamic market responses imply a greater reliance on plantations in productive regions, allowing large areas of natural forest in low‐valued regions to remain largely intact. Sensitivity analysis suggests that price, harvest, and management are most sensitive to the rate of demand increase, the interest rate, the cost of plantations, and access costs of natural forests. Two forest conservation strategies are examined which predict the system‐wide implications of forest conservation in Europe and North America. The policies indicate that whereas set asides can induce net conservation, harvests increase elsewhere, particularly in natural forests.
The Importance of Learning in the Adoption of High‐Yielding Variety Seeds
Authors: Cameron Lisa A.
Published: July 2006

To date, due to the lack of panel data, most micro‐level empirical studies of technology adoption have used cross‐sectional data. These studies cannot examine the dynamic processes of adoption such as learning. This article uses panel data to study the adoption of a new high‐yielding variety seed. First, it establishes that learning is an important variable in the adoption process. Second, it establishes that cross‐sectional estimates of a dynamic process are biased but that the extent of this bias may be small. Third, it illustrates the econometric methods needed to estimate a dynamic model when controlling for unobserved household heterogeneity.
International Marketing Margins for Agricultural Products: Effects of Some Nontariff Trade Barriers
Authors: Gallagher Paul
Published: July 2006

Trade uncertainty occurs when quality changes or when Administrative Trade Barriers (ATBs) cause a chance that a commodity will not enter the import market. Trade uncertainty adversely affects marketing firms and commodity trade. But arbitrage still precludes the distribution of rents to middlemen. An exporter subsidy may correct price distortions and expand trade towards the highest world welfare. The case for intervention appears strongest in thin markets with a low number of trade transactions and perishable commodities. Nonetheless, promoting trade liberalization before other interventions may still make sense when ATBs are present because reduced trade uncertainty also improves world welfare.
Fringe Benefits Provision by Rural Small Businesses
Authors: Variyam Jayachandran N. , Kraybill David S.
Published: July 2006

We examine the relationship between employer size and the provision of fringe benefits in a large sample of rural businesses. A clear employer size‐benefits relationship exists only in the case of health insurance, while other benefits are not strongly linked to employer size. The negative relationship between employer size and health insurance is weaker, though still existent, in businesses whose employees have relatively high skill levels. Single, independent establishments and sole proprietorships are less likely to provide fringe benefits than multi‐establishment and corporate firms.
The Effects of Breeding Stock Productivity on the U.S. Beef Cattle Cycle
Authors: Marsh John M.
Published: July 2006

The effects of breeding stock productivity on the U.S. beef cattle cycle were econometrically estimated. Growth in output per beef cow was hypothesized to impact inventory response via cattle prices and marketing alternatives. Beef productivity included carcass weights of steers, heifers, and cull cows but excluded carcass weights of dairy cattle and cattle imports. Results indicate that from ten years to an equilibrium period, the beef cow herd averaged 0.5% to 2.5% smaller compared to if zero productivity growth had occurred. In addition, productivity growth decreased the inventory elasticity of supply by 18% between 1960–74 and 1975–96.
Economics of Antipoaching Enforcement and the Ivory Trade Ban
Authors: Bulte Erwin H. , van Kooten G. Cornelis
Published: July 2006

A model of elephant conservation that includes illegal poaching, enforcement effort, and legal culling is used to analyze enforcement and elephant populations for alternative policies, with and without legal trade in ivory. Consistent with previous theoretical models, banning trade may increase or decrease equilibrium stocks. As an empirical application, information for Zambia, along with sensitivity analysis, are used to show that the ivory trade ban is more effective in conserving the African elephant (Loxodonta africana) than in permitting open trade. However, in all situations, current elephant populations likely exceed optimal levels as perceived by the range states, and further reductions in elephant numbers might be expected.
An Analysis of Ill‐Posed Production Problems Using Maximum Entropy
Authors: Paris Quirino , Howitt Richard E.
Published: July 2006

Production economics problems are often ill‐posed. This means that the number of parameters to be estimated is greater than the number of observations. In this article we show how to recover flexible cost functions from very limited data sets using a maximum entropy approach. We also argue that there exists a continuum of analysis between mathematical programming and traditional econometric techniques which is based solely upon the available information. The limiting case of a multi‐output cost function recovered using only a single observation of a farmer's allocation decisions can be easily extended to handle more than one observation.
Nonparametric Estimation of Crop Yield Distributions: Implications for Rating Group‐Risk Crop Insurance Contracts
Authors: Goodwin Barry K. , Ker Alan P.
Published: July 2006

We use nonparametric density estimation procedures to evaluate county‐level crop yield distributions. Implications for rating area‐yield crop insurance contracts are discussed. The procedures developed are used to measure yield risk and calculate insurance premium rates for wheat and barley in the 1995–96 Group Risk Program.
Allocative Efficiency, Traditional Agriculture, and Risk
Authors: Dillon John L. , Anderson J. R.
Published: July 2006

A decision theory approach is presented for the assessment of allocative efficiency from cross‐section production function estimates. Reappraisal of some of the evidence previously adduced gives only mixed support to the hypothesis of profit‐maximizing behavior by farmers in traditional agricultures. It is suggested that scope remains for investigation of the alternative hypothesis of utility maximization which, unlike profit maximization, explicitly allows for subjective risk considerations and might therefore provide a more realistic basis for policies aimed at the modernization of traditional agricultures.
Cognitive Reactivity to Sad Mood Provocation and the Prediction of Depressive Relapse
Authors: Segal Zindel V. , Kennedy Sidney , Gemar Michael , Hood Karyn , Pedersen Rebecca , Buis Tom
Published: July 2006

Context

Episode remission in unipolar major depression, while distinguished by minimal symptom burden, can also be a period of marked sensitivity to emotional stress as well as an increased risk of relapse.

Objective

To examine whether mood-linked changes in dysfunctional thinking predict relapse in recovered patients who were depressed.

Design

In phase 1 of this study, patients with major depressive disorder were randomly assigned to receive either antidepressant medication or cognitive behavior therapy. In phase 2, patients who achieved clinical remission underwent sad mood provocation and were then observed with regular clinical assessments for 18 months.

Setting

Outpatient psychiatric clinics at the Centre for Addiction and Mental Health, Toronto, Ontario.

Participants

A total of 301 outpatients with major depressive disorder, aged 18 to 65 years, participated in phase 1 of this study and 99 outpatients with major depressive disorder in remission, aged 18 to 65 years, participated in phase 2.

Main Outcome Measure

Occurrence of a relapse meetingDSM-IVcriteria for a major depressive episode as assessed by the longitudinal interval follow-up evaluation and a Hamilton Depression Rating Scale score of 16 or greater.

Results

Patients who recovered through antidepressant medication showed greater cognitive reactivity following the mood provocation than those who received cognitive behavior therapy. Regardless of type of prior treatment, the magnitude of mood-linked cognitive reactivity was a significant predictor of relapse over the subsequent 18 months. Patients whose mood-linked endorsement of dysfunctional attitudes increased by a minimum of 8 points had a significantly shorter time to relapse than those whose scores were not as elevated.

Conclusions

The vulnerability of remitted depressed patients for illness relapse may be related to the (re)activation of depressive thinking styles triggered by temporary dysphoric states. This is the first study to link such differences to prognosis following successful treatment for depression. Further understanding of factors predisposing to relapse/recurrence in recovered patients may help to shorten the potentially lifelong course of depression.
Controlled blunt microdissection for percutaneous recanalization of lower limb arterial chronic total occlusions: A single center experience
Authors: Mossop Peter J. , Amukotuwa Shalini A. , Whitbourn Robert J
Published: July 2006

Background: Percutaneous techniques for the revascularization of symptomatic lower limb arterial chronic total occlusions (CTOs) remain suboptimal due to difficulty in safely and reliably crossing these heavily calcified lesions using standard guidewire and balloon technology. Objectives: The objective of this prospective study was to evaluate the technical success and safety of controlled blunt microdissection (CMD) for the treatment of resistant peripheral CTOs. Methods: This series enrolled 36 patients (26 men; mean age 67 ± 12 years), with 44 symptomatic CTOs (2 terminal aortic, 24 iliac, 16 femoral, and 2 popliteal), which had previously failed conventional percutaneous revascularization. CMD was carried out using a specialized prototype catheter. Actuation of the hinged jaws of this CMD catheter created a channel within the occluded arterial segment for guidewire passage, and subsequent angioplasty and stenting using standard procedures. The problem of subintimal CMD catheter passage, creating an eccentric channel, was addressed using a second novel device, the true‐lumen reentry (LRE) catheter, which allowed reentry into the downstream lumen. Results: Procedural success, evaluated angiographically, was achieved in 40 (91%) of the 44 CTOs. Fourteen (35%) of these 40 successful recanalizations required guidewire redirection, using the LRE catheter for lesion traversal. There were no complications related to CMD per se; although one patient experienced acute in‐stent thrombosis, managed successfully with intra‐arterial thrombolysis. Conclusions: We therefore conclude that CMD can be used safely and successfully to facilitate recanalization of resistant CTOs in the pelvic and lower limb arteries. © 2006 Wiley‐Liss, Inc.
Feasibility study of the use of the TandemHeart® percutaneous ventricular assist device for treatment of cardiogenic shock
Authors: Burkhoff Daniel , O'Neill William , Brunckhorst Corinna , Letts Dustin , Lasorda David , Cohen Howard A.
Published: July 2006

Background: The mortality of cardiogenic shock (CGS) remains high despite currently available pharmacological and mechanical treatment options. The standard of care in medically refractory situations has been the insertion of an intra‐aortic balloon pump. The purpose of this study was to investigate the feasibility, safety, and hemodynamic impact of the TandemHeart® percutaneous left ventricular assist device (pVAD) in CGS. Methods: Thirteen patients from five centers in the US with the diagnosis of CGS were enrolled in the study. Hemodynamic measurements, including cardiac index (CI), mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) were performed presupport, during support and after device removal. Patients were monitored for 6 months. Results: The pVAD was successfully implanted in all 13 patients, with duration of support averaging 60 ± 44 hr. During support, CI increased from 2.09 ± 0.64 at baseline to 2.53 ± 0.65 (P = 0.02), MAP increased from 70.6 ± 11.1 to 81.7 ± 14.6 (P = 0.01), PCWP decreased from 27.2 ± 12.2 to 16.5 ± 4.8 (P = 0.01), and CVP from 12.9 ± 3.7 to 12.6 ± 3.6 (P = NS). Ten patients survived to device explant, 6 of whom were bridged to another therapy. Seven patients survived to hospital discharge and were all alive at 6 months. The two most common adverse events were distal leg ischemia (n = 3) and bleeding from the cannulation site (n = 4). Conclusion: The TandemHeart® PTVA System may be a useful complementary treatment for patients with CGS, especially as a bridge to another treatment. Further study is needed to definitively establish safety and efficacy. © 2006 Wiley‐Liss, Inc.
Prevention of arterial spasm during percutaneous coronary interventions through radial artery: The SPASM study
Authors: Varenne Olivier , Jégou Arnaud , Cohen Remy , Empana Jean Philippe , Salengro Emmanuel , Ohanessian Alice , Gaultier Cédric , Allouch Philippe , Walspurger Sylvie , Margot Olivier , El Hallack Abdel , Jouven Xavier , Weber Simon , Spaulding Christian
Published: July 2006

Aims: Radial artery spasm remains the major limitation of transradial approach for percutaneous coronary interventions. The aim of our study was to evaluate the efficacy of vasodilators in the prevention of radial artery spasm during percutaneous coronary interventions. Methods and results: 1,219 patients were consecutively randomized to receive placebo (n = 198), molsidomine 1 mg (n = 203), verapamil 2.5 mg (n = 409), 5 mg (n = 203) or verapamil 2.5 mg and molsidomine 1 mg (n = 206). All drugs were administered through the arterial sheath. The primary end point was the occurrence of a radial artery spasm defined by the operator as severe limitation of the catheter movement, with or without angiographic confirmation. Main characteristics including age, sex, wrist and arterial sheath diameters and procedure duration were identical across the groups. The rate of radial artery spasm was lowest in patients receiving verapamil and molsidomine (4.9%), compared to verapamil 2.5 mg or 5 mg (8.3 and 7.9%), or molsidomine 1 mg (13.3%); and placebo (22.2%) (P < 0.0001). Conclusion: Radial artery spasm during transradial percutaneous interventions was effectively prevented by the administration of vasodilators. The combination of verapamil 2.5 mg and molsidomine 1 mg provided the strongest relative risk reduction of spasm compared to placebo and should therefore be recommended during percutaneous coronary interventions through the radial approach. © 2006 Wiley‐Liss, Inc.
Phase Equilibrium in Binary Systems AIVBVI. Part 3. Systems Sn—Chalcogenides
Authors: Bletskan D. I.
Published: July 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Light and Singlet Oxygen in Plant Defense Against Pathogens: Phototoxic Phenalenone Phytoalexins
Authors: Flors Cristina , Nonell Santi
Published: July 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Controlled Microwave Heating as an Enabling Technology: Expedient Synthesis of Protease Inhibitors in Perspective
Authors: Larhed Mats , Wannberg Johan , Hallberg Anders
Published: July 2006

Since the early days of organic chemistry, oil baths, hot plates, metal blocks, and isomantles have been the heating devices of choice for driving chemical reactions. Over the last years, microwave heating has evolved as a well‐demonstrated alternative to classic heating with the potential to emerge as the preferred heating method in organic synthesis. In this perspective, we will illustrate that microwave heating has an edge over conventional heating also in medicinal and high‐throughput chemistry applications, enabling both an expanded reaction range and the diminishing of reaction times from many hours or days down to minutes. By focusing on the development of protease inhibitors, we present a series of successful lead optimizations starting from complex core structures and using controlled microwave heating as the energy source. In short, hundreds of protease inhibitors have been quickly synthesized under microwave irradiation since the start of our high‐speed program back in 1998.
QSAR Studies Related to Toxicity of Aromatic Compounds on Tetrahymena Pyriformis
Authors: Laszlo Tarko , Beteringhe Adrian
Published: July 2006

Results of some QSAR studies in which the training set contained aromatic compounds with toxic effect onTetrahymena pyriformisare presented. The QSAR studies reveal the existence of two classes of compounds – with and without hydrogen bonds – for which the calculation of some QSAR separated equations are recommended. QSAR equations obtained for the two classes of aromatic compounds have good predictive powers:N=87,p=6,r2=0.7962,s=0.3178, andN=113,p=5,r2=0.8950,s=0.2637, respectively. For the compounds with hydrogen bonds, “moment of inertiaB” and “QSPR of percentage of mass fragments” are molecular characteristics with a powerful influence on toxicity values, and logKowhas a moderate influence. For compounds without hydrogen bonds “bonds number weighted total energy” and “LUMO‐HOMO gap weighted molecular volume” are the molecular characteristics with a powerful effect on toxicity values, and topological descriptor AAA has a moderate effect.
Perennial grasses for turf, sport and amenity uses: evolution of form, function and fitness for human benefit
Authors: CASLER M. D.
Published: July 2006

The history of genetic modification and improvement of perennial grasses used for turf and sport can be traced back to the earliest events leading to the evolution of traits such as perenniality, asexual reproduction by rhizomes or stolons, apical dominance and hardening or acclimation responses to environmental stress. Human influences on perennial grasses likely began with the dawn of agriculture and the domestication of livestock about 8–10000 years ago with the movement of grasses from forest margins and meadows to pastures and cropland. As agrarian cultures found more time for leisure and recreation, perennial grasses became multi-functional, taking on a greater role with the invention of ball games, sports and a sod industry. Early human selection of superior turf grasses was largely based on individual clones that were vegetatively propagated for commercial purposes, dating back as far as 12th century Japan. The science of turf breeding began in 1962 with the initiation of extensive efforts to collect superior clones from old turf sods in highly stressful environments, followed by numerous cycles of recurrent selection for turf traits in harsh environments and under realistic mowing regimes. These efforts spawned many public and commercial breeding ventures and thousands of cultivars that have spread throughout the world, improving the quality, persistence and functionality of turf for many uses.
Gastrointestinal nematode species burdens and host mortality in a feral sheep population
Authors: CRAIG B. H. , PILKINGTON J. G. , PEMBERTON J. M.
Published: July 2006

Every few years a large proportion of the feral sheep on Hirta, St Kilda die due to food shortage. The effects of malnutrition are exacerbated by gastrointestinal nematodes. As found in sheep flocks in mainland Britain,Teladorsagia circumcinctahas long been considered the predominant and most pathogenic nematode species in all age classes of Soay sheep. Previous research indicated that intensity of this species showed a negative association with host age and comprised 75% of the entire gastrointestinal burden. Here we present new data that showTrichostrongylus axeiandTrichostrongylus vitrinusto be the predominant worm pathogens in young Soay sheep. In the present study,Trichostrongylusspp. burdens declined with host age whereasT. circumcinctaactually increased in burden over the first few age classes. Also, male hosts had significantly higher burdens ofTrichostrongylusspp. than females, with this genus making up a higher proportion of the strongyle egg producing community in male hosts than female hosts. These new findings raise questions concerning our previous interpretation of the main nematode species contributing to strongyle egg count in the population, and the contrasting infection patterns of these nematode species in unmanaged St Kilda Soay sheep compared with domestic sheep in mainland Britain.
Hepatitis A virus in urban sewage from two Mediterranean countries
Authors: PINTÓ R. M. , ALEGRE D. , DOMÍNGUEZ A. , EL-SENOUSY W. M. , SÁNCHEZ G. , VILLENA C. , COSTAFREDA M. I. , ARAGONÈS L. , BOSCH A.
Published: July 2006

Molecular methods for the detection and typing of hepatitis A virus (HAV) strains in sewage were applied to determine its distribution in Cairo and Barcelona. The study revealed the occurrence of different patterns of hepatitis A endemicity in each city. The circulating strains characterized, whether in Cairo or Barcelona, were genotype IB. The effects of a child vaccination programme and the increase in the immigrant population on the overall hepatitis A occurrence in Barcelona were evaluated. While vaccination contributed to a significant decrease in the number of clinical cases, the huge recent immigration flow has probably been responsible for the re-emergence of the disease in the last year of study, in the form of small outbreaks among the non-vaccinated population.
Concepts and Approaches Towards Understanding the Cellular Redox Proteome
Authors: Ströher E. , Dietz K.‐J.
Published: July 2006

Abstract: The physiological activity of a significant subset of cell proteins is modified by the redox state of regulatory thiols. The cellular redox homeostasis depends on the balance between oxidation of thiols through oxygen and reactive oxygen species and reduction by thiol‐disulfide transfer reactions. Novel and improved methodology has been designed during recent years to address the level of thiol/disulfide regulation on a genome‐wide scale. The approaches are either based on gel electrophoresis or on chromatographic techniques coupled to high end mass spectrometry. The review addresses diagonal 2D‐SDS‐PAGE, targeted identification of specific redox‐interactions, affinity chromatography with thioredoxins and glutaredoxins, gel‐based and non‐gel based labelling techniques with fluorophores (such as Cy3, Cy5, ICy), radioisotopes, or with isotope‐coded affinity tags (ICAT), differential gel electrophoresis (DIGE) and combined fractional diagonal chromatography (COFRADIC). The extended methodological repertoire promises fast and new insight into the intricate regulation network of the redox proteome of animals, bacteria, and plants.
Stomatal Conductance is a Key Parameter to Assess Limitations to Photosynthesis and Growth Potential in Barley Genotypes
Authors: Jiang Q. , Roche D. , Monaco T. A. , Hole D.
Published: July 2006

Abstract: Fourteen genotypes of barley were compared for response to salinity by monitoring the parameters gas exchange and chlorophyll fluorescence. We present relationships between stomatal conductance (gs) gas exchange chlorophyll fluorescence parameters and aboveground dry matter (AGDM). We found that genetic variability provided a continuum of data for gs across control and saline conditions. We used this continuum of gs values to test the overall relationships between gs and net photosynthesis (A), leaf internal CO2 concentration (Ci), actual quantum yield of PSII electron transport (ΦPSII), relative electron yield over net CO2 assimilation rate (ETR/A), and AGDM. The relationship between gs and A was highly significant (p < 0.0001) for both control and saline treatments, while correlations between gs and Ci, and Ci and A were significant only under control conditions. Unexpectedly, we found positive correlations between gs and ΦPSII (p < 0.0001) for both conditions. A comparison between relationships of gs and A, and gs and ΦPSII seemed to indicate a possible acclimation to salinity at the chloroplastic level. Finally, the relationships between gs and ETR/A were exceptionally strong for both growing conditions (p < 0.0001) indicating that, as gs values were negatively affected in barley by genetics and salinity as main or interactive effects, there was a progressive increase in photorespiration in barley. Overall, we found that stomatal conductance was a key parameter in the study of barley responses to limiting situations for photosynthesis. We also found a strong relationship between AGDM and gs regardless of growing conditions and genotypes. For breeding evaluations to select barley genotypes for salinity tolerance, it may be possible to replace all measurements of gas exchange and chlorophyll fluorescence by the simple use of a porometer.
Labor and Housing Markets as Public Spaces: ‘Personal Responsibility’ and the Contradictions of Welfare-Reform Policies
Authors: Trudeau Daniel , Cope Meghan
Published: July 2006

Recent US welfare-form initiatives affecting employment and housing assistance have promoted more flexible applications of assistance as well as devolving the responsibility of care for the poor from federal levels to the individual. Implicit in these policy changes is the assumption that individuals enter labor and housing markets where open access is the norm and a ‘level playing field’ exists. In this paper, we use the analogy of seeing labor and housing markets as public spaces to analyze how the ideals of democratic capitalism in labor and housing markets exist normatively, but are always violated in practice. We argue that the influence of neoliberalism, and the devolution of welfare responsibility to the individual in particular, have led to policy changes that neglect issues of unequal access connected to hierarchies of race and gender and their spatial manifestations. Welfare reform in the specific areas of employment and housing assistance has promoted the primacy of private markets as essential components to ensuring social welfare. These reforms have super-ficially opened more options to recipients of public assistance while simultaneously allowing to continue the instruments, institutions, and structural forces that constrain practical access to the full range of jobs and housing. We argue that efforts to maintain these markets have not been distributed to measures ensuring fair play of participants. As a consequence, some problematic contradictions between policy and practice call into question the suitability of the private market as a strategy of providing welfare for the poor.
Women and the Work of Community
Authors: Staeheli Lynn A
Published: July 2006

The term ‘community’ is an integral part of the discourse regarding social-service and human-service delivery in the United States, Canada, Australia, and the United Kingdom. Yet, there are a host of meanings and goals that are part of the project of community; these meanings reflect the ambiguous position of community with respect to ideas of publicity and privacy. In this paper I explore some of those meanings and goals through the use of interviews with women who work in nonprofit, community-based organizations that support human and social services. The focus is on the ways in which the women frame the concept of community and the ways in which these may be part of a strategy to create political and material spaces for caring, empowerment, and justice.
Microtubule bundling and nested buckling drive stripe formation in polymerizing tubulin solutions
Authors: Liu Yifeng , Guo Yongxing , Valles James M. , Tang Jay X.
Published: July 2006

Various mechanisms govern pattern formation in chemical and biological reaction systems, giving rise to structures with distinct morphologies and physical properties. The self-organization of polymerizing microtubules (MTs) is of particular interest because of its implications for biological function. We report a study of the microscopic structure and properties of the striped patterns that spontaneously form in polymerizing tubulin solutions and propose a mechanism driving this assembly. Microscopic observations reveal that the pattern comprises wave-like MT bundles. The retardance of the solution and the fluorescence intensity of labeled MTs vary periodically in space, suggesting a coincident periodic variation in MT alignment and density. This wave-like structure forms through the development and coordinated buckling of initially aligned MT bundles. Both static magnetic fields and convective flow can induce the initial alignment. The nesting of the buckled MT bundles gives rise to density variations that are in quantitative accord with the data. We further propose that the buckling wavelength is selected by a balance between the bending energy of the bundles and the elastic energy of the MT network surrounding them. These studies reveal a unique physical chemical mechanism by which mechanical buckling couples with protein polymerization to produce macroscopic patterns. Self-organization of this type may be important to the formation of certain biological structures.
Packing, tiling, and covering with tetrahedra
Authors: Conway J. H. , Torquato S.
Published: July 2006

It is well known that three-dimensional Euclidean space cannot be tiled by regular tetrahedra. But how well can we do? In this work, we give several constructions that may answer the various senses of this question. In so doing, we provide some solutions to packing, tiling, and covering problems of tetrahedra. Our results suggest that the regular tetrahedron may not be able to pack as densely as the sphere, which would contradict a conjecture of Ulam. The regular tetrahedron might even be the convex body having the smallest possible packing density.
Theories and measures of consciousness: An extended framework
Authors: Seth Anil K. , Izhikevich Eugene , Reeke George N. , Edelman Gerald M.
Published: July 2006

A recent theoretical emphasis on complex interactions within neural systems underlying consciousness has been accompanied by proposals for the quantitative characterization of these interactions. In this article, we distinguish key aspects of consciousness that are amenable to quantitative measurement from those that are not. We carry out a formal analysis of the strengths and limitations of three quantitative measures of dynamical complexity in the neural systems underlying consciousness: neural complexity, information integration, and causal density. We find that no single measure fully captures the multidimensional complexity of these systems, and all of these measures have practical limitations. Our analysis suggests guidelines for the specification of alternative measures which, in combination, may improve the quantitative characterization of conscious neural systems. Given that some aspects of consciousness are likely to resist quantification altogether, we conclude that a satisfactory theory is likely to be one that combines both qualitative and quantitative elements.
Whence cometh the allosterome?
Authors: Lindsley Janet E. , Rutter Jared
Published: July 2006

Regulation of cellular functions can be accomplished by many mechanisms, including transcriptional regulation, alternative splicing, translational regulation, phosphorylation and other posttranslational covalent modifications, degradation, localization, protein–protein interactions, and small-molecule allosteric effectors. Largely because of advances in the techniques of molecular biology in the past few decades, our knowledge of regulation by most of these mechanisms has expanded enormously. Regulation by small-molecule, allosteric interactions is an exception. Many of the best-known allosteric regulators were discovered decades ago, when we knew little about all of these other forms of regulation. Allostery is the most direct, rapid, and efficient regulatory mechanism to sense changes in the concentration of small molecules and alter cellular responses to maintain homeostasis. In this perspective, we present the argument that allosteric regulation is underappreciated in the systems biology world and that many allosteric effectors remain to be discovered.
PlyC: A multimeric bacteriophage lysin
Authors: Nelson Daniel , Schuch Raymond , Chahales Peter , Zhu Shiwei , Fischetti Vincent A.
Published: July 2006

Lysins are murein hydrolases produced by bacteriophage that act on the bacterial host cell wall to release progeny phage. When added extrinsically in their purified form, these enzymes produce total lysis of susceptible Gram-positive bacteria within seconds, suggesting a unique antimicrobial strategy. All known Gram-positive lysins are produced as a single polypeptide containing a catalytic activity domain, which cleaves one of the four major peptidoglycan bonds, and a cell-wall-binding domain, which may bind a species-specific carbohydrate epitope in the cell wall. Here, we have cloned and expressed a unique lysin from the streptococcal bacteriophage C
1
, termed PlyC. Molecular characterization of the
plyC
operon reveals that PlyC is, surprisingly, composed of two separate gene products, PlyCA and PlyCB. Based on biochemical and biophysical studies, the catalytically active PlyC holoenzyme is composed of eight PlyCB subunits for each PlyCA. Inhibitor studies predicted the presence of an active-site cysteine, and bioinformatic analysis revealed a cysteine, histidine-dependent amidohydrolase/peptidase domain within PlyCA. Point mutagenesis confirmed that PlyCA is responsible for the observed catalytic activity, and Cys-333 and His-420 are the active-site residues. PlyCB was found to self-assemble into an octamer, and this complex alone was able to direct streptococcal cell-wall-specific binding. Similar to no other proteins in sequence databases, PlyC defines a previously uncharacterized structural family of cell-wall hydrolases.
Signaling across the synapse: a role for Wnt and Dishevelled in presynaptic assembly and neurotransmitter release
Authors: Ahmad-Annuar Azlina , Ciani Lorenza , Simeonidis Iordanis , Herreros Judit , Fredj Naila Ben , Rosso Silvana B. , Hall Anita , Brickley Stephen , Salinas Patricia C.
Published: July 2006

Proper dialogue between presynaptic neurons and their targets is essential for correct synaptic assembly and function. At central synapses, Wnt proteins function as retrograde signals to regulate axon remodeling and the accumulation of presynaptic proteins. Loss of Wnt7a function leads to defects in the localization of presynaptic markers and in the morphology of the presynaptic axons. We show that loss of function of Dishevelled-1 (Dvl1) mimics and enhances the Wnt7a phenotype in the cerebellum. Although active zones appear normal, electrophysiological recordings in cerebellar slices from Wnt7a/Dvl1 double mutant mice reveal a defect in neurotransmitter release at mossy fiber–granule cell synapses. Deficiency in Dvl1 decreases, whereas exposure to Wnt increases, synaptic vesicle recycling in mossy fibers. Dvl increases the number of Bassoon clusters, and like other components of the Wnt pathway, it localizes to synaptic sites. These findings demonstrate that Wnts signal across the synapse on Dvl-expressing presynaptic terminals to regulate synaptic assembly and suggest a potential novel function for Wnts in neurotransmitter release.
A major histocompatibility complex class I–dependent subset of memory phenotype CD8+ cells
Authors: Boyman Onur , Cho Jae-Ho , Tan Joyce T. , Surh Charles D. , Sprent Jonathan
Published: July 2006

Most memory phenotype (MP) CD44hi CD8+ cells are resting interleukin (IL)-15–dependent cells characterized by high expression of the IL-2/IL-15 receptor β (CD122). However, some MP CD8+ cells have a CD122lo phenotype and are IL-15 independent. Here, evidence is presented that the CD122lo subset of MP CD8+ cells is controlled largely by major histocompatibility complex (MHC) class I molecules. Many of these cells display surface markers typical of recently activated T cells (CD62Llo, CD69hi, CD43hi, and CD127lo) and show a high rate of background proliferation. Cells with this phenotype are highly enriched in common γ chain–deficient mice and absent from MHC-I−/− mice. Unlike CD122hi CD8+ cells, CD122lo MP CD8+ cells survive poorly after transfer to MHC-I−/− hosts and cease to proliferate. Although distinctly different from typical antigen-specific memory cells, CD122lo MP CD8+ cells closely resemble the antigen-dependent memory CD8+ cells found in chronic viral infections.
Expression of interleukin (IL)-2 and IL-7 receptors discriminates between human regulatory and activated T cells
Authors: Seddiki Nabila , Santner-Nanan Brigitte , Martinson Jeff , Zaunders John , Sasson Sarah , Landay Alan , Solomon Michael , Selby Warwick , Alexander Stephen I. , Nanan Ralph , Kelleher Anthony , de St. Groth Barbara Fazekas
Published: July 2006

Abnormalities in CD4+CD25+Foxp3+ regulatory T (T reg) cells have been implicated in susceptibility to allergic, autoimmune, and immunoinflammatory conditions. However, phenotypic and functional assessment of human T reg cells has been hampered by difficulty in distinguishing between CD25-expressing activated and regulatory T cells. Here, we show that expression of CD127, the α chain of the interleukin-7 receptor, allows an unambiguous flow cytometry–based distinction to be made between CD127lo T reg cells and CD127hi conventional T cells within the CD25+CD45RO+RA− effector/memory and CD45RA+RO− naive compartments in peripheral blood and lymph node. In healthy volunteers, peripheral blood CD25+CD127lo cells comprised 6.35 ± 0.26% of CD4+ T cells, of which 2.05 ± 0.14% expressed the naive subset marker CD45RA. Expression of FoxP3 protein and the CD127lo phenotype were highly correlated within the CD4+CD25+ population. Moreover, both effector/memory and naive CD25+CD127lo cells manifested suppressive activity in vitro, whereas CD25+CD127hi cells did not. Cell surface expression of CD127 therefore allows accurate estimation of T reg cell numbers and isolation of pure populations for in vitro studies and should contribute to our understanding of regulatory abnormalities in immunopathic diseases.
Police suicide: an overview
Authors: Miolanti John M.
Published: July 2006

Police work is an occupation replete with psychological stress and trauma, danger, and availability of firearms. Under such conditions, one might expect an increased risk of suicide, and police suicide rates have appeared to increase over the past decade. In this article, we discuss relationships of occupational stress, availability of firearms, alcohol use, and retirement with police suicide. Also discussed are suggestions for reducing police suicide, including intervention programs, suicide awareness training, and increasing the accuracy of police suicide rates to increase awareness for police organizational prevention policies.
Puberty stage and spontaneous descent of acquired undescended testis: implications for therapy?
Authors: Sijstermans K. , Hack W. W. M. , Van Der Voort‐Doedens L. M. , Meijer R. W. , Haasnoot K.
Published: July 2006

We assessed spontaneous descent of acquired undescended testis (UDT) at puberty. 299 Boys (aged 1.2–16.5 years, mean 9.4) with 350 acquired‐UDT were examined annually during a 12.6‐year period (mean 3.1). An acquired‐UDT was defined as a previously intrascrotal testis which can no longer be manipulated into a stable scrotal position. Each year, position of the testis and pubertal development according to Tanner's stages were assessed. Early puberty was defined as puberty stage G2 (testicular volume 4–9 mL), mid‐puberty as puberty stages G3 (testicular volume 10 mL) and G4 (testicular volume 11–15 mL), and late puberty as puberty stage G5 (testicular volume >15 mL). Follow‐up was completed if spontaneous descent had occurred, if mid‐pubertal orchidopexy (ORP) had to be performed, if the boy was lost for follow‐up, or if pre‐pubertal ORP was performed in another hospital. In 139 boys with 164 acquired‐UDT follow‐up was meanwhile completed. Twelve boys with 14 UDT were lost for follow‐up. In an additional 16 boys with 21 UDT, ORP was performed in another hospital. In 98 of the remaining 129 (76.0%) acquired‐UDT spontaneous descent at puberty occurred. Mean follow‐up was 2.5 years (range 0.2–8.5). In 70 of 98 testes (71.4%) descent occurred in early puberty, in 26 of 98 testes (26.5%) in mid‐puberty, and in two testes in late puberty. In 31 of 129 testes (24.0%) ORP had to be performed at mid (30 cases) or late (one case) puberty. In this series, 98 of 129 acquired‐UDT (76.0%) descended spontaneously at puberty, whereas in 31 of 129 (24.0%) pubertal ORP was performed. If ORP is postponed until puberty stage G3 (testicular volume of 10 mL) three of four acquired‐UDT will descend spontaneously.
Pattern of paediatric maxillofacial fractures in Lagos, Nigeria
Authors: OGUNLEWE M. O. , JAMES O. , LADEINDE A. L. , ADEYEMO W. L.
Published: July 2006

Summary.  Background.  Maxillofacial fractures in children are rare when compared to those occurring in adults.

Aim.  To establish the incidence, pattern, and aetiology of maxillofacial fractures in children aged 15 years and below in Lagos, Nigeria.

Design.  A review of patients with maxillofacial fractures aged 15 years and below seen and treated at the Lagos University Teaching Hospital, Lagos, Nigeria between January 1997 and December 2004 was conducted.

Results.  Of the 225 patients with maxillofacial fractures seen within the study period, 37 (16·4%) were children aged 15 years and below, with a male‐to‐female ratio of 1·5 : 1. The highest incidence recorded was found within the age group 12–15 years (41%), with the lowest incidence occurring in the age group 0–5 years (27%). Multiple fractures were commoner in older patients (P > 0·05), and in boys (P > 0·05). There were no statistically significant relationships between the age of the patients, gender distribution, and mechanisms of injury. Road traffic crashes were the most common aetiological factor (64·9%), with the mandible being the most involved facial bone (63·8%). Majority of the mandibular fractures (33·3%) were located in parasymphyseal region. Zygomatic complex fractures were the most common in the mid‐facial region. Most of the fractures (81·1%) were immobilized by simple methods (arch bars, eyelet wires, acrylic splint with circum‐mandibular wiring) with or without intermaxillary fixation. Of the cases, 18·9% were managed conservatively.

Conclusion.  The incidence of facial fractures in this study was found to be higher than previously reported in Nigeria and worldwide, with almost two‐thirds of cases a result of road traffic crashes. There is a need to enforce legislation aimed at preventing road traffic crashes to reduce maxillofacial injuries in children.
Predictors of recruitment for willows invading riparian environments in south‐east Australia: implications for weed management
Authors: STOKES KATE E. , CUNNINGHAM SAUL A.
Published: July 2006

Predicting geographical areas susceptible to weed invasion is a primary target for land managers. Willows (Salix spp.) invading riparian environments have recently been increasing in number in south‐east Australia. In order to prioritize management decisions, a clear understanding of the factors affecting recruitment success for sexually and asexually generated Salix recruits is vital.

Multiple variables are hypothesized to determine the spatial distribution of Salix recruits. Therefore an information–theoretic model comparison (ITMC) approach was used to analyse factors determining the abundance and distribution of Salix recruits along four rivers in south‐east Australia with differing flow regulation. Generalized linear modelling techniques were applied to multiparameter candidate models, developed from existing knowledge of the system and plausible hypotheses. Predictor variables included parameters describing river disturbance, availability of propagule sources and competition for recruitment space.

Models of sexually produced Salix recruits performed well, generating 95% confidence sets of candidate models that were small relative to the potential set of models analysed (18%), whereas models of asexual recruits performed less well, indicated by 95% confidence sets that were large relative to the potential set of models explored (67%).

A multimodel inference approach was required: model results indicated that availability of mating partners in the environment plays an important role in determining the abundance of sexually derived Salix recruits, whereas for asexual recruits river disturbance parameters better predicted abundance.

For the models of sexual reproduction, model plausibility was strengthened by corroborative results from an independent data set collected in the same geographical region. However, the validation data set was too small to assess the predictive capability of the model‐averaged model.

Synthesis and applications. Information–theoretic model selection methods helped clarify the relative importance of different model parameters on the abundance of Salix recruits. Knowledge of the link between river regulation and willow recruitment enables a greater degree of management flexibility in response to risk forecasting under future scenarios for different water flows. Targeting control programmes to focus on removal of female and seeding willows in rivers with low levels of disturbance may eliminate Salix recruits altogether, whereas the same treatment applied to high‐level disturbance rivers is likely to result in persistent problems with asexual recruits.
Pharmacokinetics and anesthetic activity of eugenol in male Sprague–Dawley rats
Authors: GUENETTE S. A. , BEAUDRY F. , MARIER J. F. , VACHON P.
Published: July 2006

Eugenol, the principle chemical constituent of clove oil, has recently been evaluated for its anesthetic and analgesic properties in fish and amphibians. The objective of this study was to determine the pharmacokinetic (PK) and anesthetic activity of eugenol in rats. Male Sprague–Dawley rats received single i.v. doses of eugenol (0, 5, 10, 20, 40 and 60 mg/kg) and anesthetic level was evaluated with the withdrawal reflex. For the 20 mg/kg dose level, blood and urinary samples were collected over 1 h for the PK assessment. Plasma and blood concentrations of eugenol, as well as metabolite identification in urine, were determined using a novel dansyl chloride derivatization method with liquid chromatography mass spectrometry (LC/MS/MS). PK parameters were calculated using noncompartmental methods. Eugenol‐induced loss of consciousness in a dose‐dependent manner, with mean (±SEM) recovery in reflex time of 167 ± 42 sec observed at the highest dose level. Mean systemic clearance (Cl) in plasma and blood were 157 and 204 mL/min/kg, respectively. Glucuronide and sulfate conjugates were identified in urine. Overall, eugenol produced a reversible, dose‐dependent anesthesia in male Sprague–Dawley rats.