bluuebunny/crossref_metadata_2025 huggingface dataset:
Targeting the mTOR Signaling Network for Cancer Therapy
Authors: Meric-Bernstam Funda , Gonzalez-Angulo Ana Maria
Published: March 2009

The serine-threonine kinase mammalian target of rapamycin (mTOR) plays a major role in the regulation of protein translation, cell growth, and metabolism. Alterations of the mTOR signaling pathway are common in cancer, and thus mTOR is being actively pursued as a therapeutic target. Rapamycin and its analogs (rapalogs) have proven effective as anticancer agents in a broad range of preclinical models. Clinical trials using rapalogs have demonstrated important clinical benefits in several cancer types; however, objective response rates achieved with single-agent therapy have been modest. Rapalogs may be more effective in combination with other anticancer agents, including chemotherapy and targeted therapies. It is increasingly apparent that the mTOR signaling network is quite complex, and rapamycin treatment leads to different signaling responses in different cell types. A better understanding of mTOR signaling, the mechanism of action of rapamycin, and the identification of biomarkers of response will lead to more optimal targeting of this pathway for cancer therapy.
Scale-factor corrections in the optical inertial sensor
Authors: Lee D-C , Han C-S
Published: March 2009

In the operations of optical inertial sensors, geometric variations due to temperature and operation environments cause thermoelastic deformations of their components, which lead to changes in the area and perimeter of their resonator block. The fluctuations in the geometric scale factor are corrected by the piezoelectric actuator. This article presents the numerical formulation of the elastic behaviour of each piezoelectric actuator, and the numerical formulations are verified through comparisons with the results of a finite element simulation.
Modelling and control of a human-like arm incorporating muscle models
Authors: Mailah M , Jahanabadi H , Zain M Z M , Priyandoko G
Published: March 2009

This article focuses on the modelling and control of a two-link planar mechanical manipulator that emulates a human arm. The simplicity of the control algorithm and its ease of computation are particularly highlighted in this study. The arm is subjected to a vibratory excitation at a specific location on the arm while performing trajectory tracking tasks in two-dimensional space, taking into account the presence of ‘muscle’ elements that are mathematically modelled. A closed-loop control system is applied using an active force control strategy to accommodate the disturbances based on a predefined set of loading and operating conditions to observe the system responses. Results of the study imply the effectiveness of the proposed method in compensating the vibration effect to produce robust and accurate tracking performance of the system. The results may serve as a useful tool in aiding the design and development of a tooling device for use in a mechatronic robot arm or even human arm (smart glove) where precise and/or robust performance is a critical factor and of considerable importance.
A direct method for determining meshing surfaces of globoidal cams with tapered roller followers
Authors: Tsay D M , Chen H P , Lin S Y
Published: March 2009

For determining the globoidal cam profile with tapered rollers radially mounted at its turret, a direct and relative simple approach is presented. The concept of the proposed procedure is based on the cam surfaces that can be represented as the swept surfaces of the tapered roller of the globoidal cam-turret mechanism in motion. For finding the swept surfaces of the tapered roller, the pitch surface yielded by the locus of the tapered roller is first generated through the rigid body transformation. Then, in the process of producing the swept surfaces for the cam surfaces, the meshing angles and meshing vectors are defined and identified by using the pitch surface of the tapered roller. Since it is not necessary to solve any non-linear contact equations usually encountered in traditional methods, such a procedure provides a convenient tool in determining the spatial cam surfaces. To demonstrate the feasibility and accuracy of the proposed approach, its analytical formulations with numerical results are compared with those obtained by an earlier technique based on the theory of screws.
Dynamic analysis of a composite beam subjected to a moving load
Authors: Rezvani M J , Khorramabadi Karami M
Published: March 2009

In this article, the dynamic analysis of an infinite Timoshenko beam made of a laminated composite located on a generalized Pasternak viscoelastic foundation is studied. The beam is subjected to a moving concentrated load. It is assumed that the mechanical properties of the beam change in the direction of the beam thickness but remain constant in the axial direction. Closed-form steady-state solutions, based on the first-order shear deformation theory, are developed. By selection of an appropriate displacement field for the composite beam, and using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained and solved through a complex infinite Fourier transformation method. The results are introduced in terms of deflection, bending moment, shear force, and stress. In addition, the effects of stiffness, shear layer viscosity coefficients of foundation, velocity of the moving load, number of layers, and various angles of layers over the beam response are studied. For some specific cases, the results are compared with those presented in some other published papers, with which good agreements are observed.
Ground propagation of vibrations from railway vehicles using a finite/infinite-element model of the soil
Authors: Kouroussis G , Verlinden O , Conti C
Published: March 2009

The purpose of this study is to investigate the generation and propagation of ground vibrations induced by railway traffic, more specifically in the case of urban vehicles. The complete vehicle—track—soil model is developed according to an uncoupled approach: the vehicle—track subsystem is first simulated so as to provide the ground forces which, in turn, are applied to the model of the soil. The vehicle—track model is built with the help of the home-made C++library
Thermohydrodynamic analysis of turbulent flow in journal bearings running under different steady conditions
Authors: Maneshian B , Nassab S A Gandjalikhan
Published: March 2009

In this study, the thermohydrodynamic (THD) characteristics of journal bearings with turbulent lubricant flow are determined using computational fluid dynamic techniques. The bearing has infinite length and operates under incompressible and steady conditions. The numerical solution of two-dimensional Navier—Stokes equations, with the equations governing the kinetic energy of turbulence and the dissipation rate, coupled with the energy equation in the lubricant flow and the heat conduction equation in the bearing is carried out. The AKN low- Re k–ε turbulence model is employed for computation of turbulence fluctuations. Because of the complex physical geometry, the governing equations are transformed for use in the computational domain such that the relation between computational and physical domains is obtained by conformal mapping. Discretized forms of the transformed equations are obtained by the control volume method and solved by the SIMPLE algorithm. Cavitation effects are also considered by using an appropriate cavitation model. The liquid fraction in the cavitated region is computed based on the continuity requirements, and rather than the two-phase flow of lubricant in this region, a homogeneous mixture with equivalent property is assumed and the governing equations still apply in the cavitated domain. In this study, the effects of Reynolds number, clearance ratio, and eccentricity ratio on THD behaviour of journal bearings are examined. Comparison between the present numerical results and experiment shows good agreement.
What Do (and Don't) We Know about the Value Added Tax? A Review of Richard M. Bird and Pierre-Pascal Gendron's The VAT in Developing and Transitional Countries
Authors: Keen Michael
Published: March 2009

The VAT has taken the tax world by storm over the last fifty years, but left little trace in the academic literature. Bird and Gendron provide an impressively informed and informative account of the VAT experience in lower income countries, largely vindicating the tax and standard advice for its design. But they rightly stress too that dominant “expert opinion” on the VAT remains troublingly uninformed by serious analysis and evidence. This article focuses on some of these gaps and recent attempts to start filling them.
A Column Generation Algorithm for Choice-Based Network Revenue Management
Authors: Bront Juan José Miranda , Méndez-Díaz Isabel , Vulcano Gustavo
Published: March 2009

During the past few years, there has been a trend to enrich traditional revenue management models built upon the independent demand paradigm by accounting for customer choice behavior. This extension involves both modeling and computational challenges. One way to describe choice behavior is to assume that each customer belongs to a segment, which is characterized by a consideration set, i.e., a subset of the products provided by the firm that a customer views as options. Customers choose a particular product according to a multinomial-logit criterion, a model widely used in the marketing literature.

In this paper, we consider the choice-based, deterministic, linear programming model (CDLP) of Gallego et al. (2004) [Gallego, G., G. Iyengar, R. Phillips, A. Dubey. 2004. Managing flexible products on a network. Technical Report CORC TR-2004-01, Department of Industrial Engineering and Operations Research, Columbia University, New York], and the follow-up dynamic programming decomposition heuristic of van Ryzin and Liu (2008) [van Ryzin, G. J., Q. Liu. 2008. On the choice-based linear programming model for network revenue management. Manufacturing Service Oper. Management 10(2) 288–310]. We focus on the more general version of these models, where customers belong to overlapping segments. To solve the CDLP for real-size networks, we need to develop a column generation algorithm. We prove that the associated column generation subproblem is indeed NP-hard and propose a simple, greedy heuristic to overcome the complexity of an exact algorithm. Our computational results show that the heuristic is quite effective and that the overall approach leads to high-quality, practical solutions.
Index Policies for the Admission Control and Routing of Impatient Customers to Heterogeneous Service Stations
Authors: Glazebrook K. D. , Kirkbride C. , Ouenniche J.
Published: March 2009

We propose a general Markovian model for the optimal control of admissions and subsequent routing of customers for service provided by a collection of heterogeneous stations. Queue-length information is available to inform all decisions. Admitted customers will abandon the system if required to wait too long for service. The optimisation goal is the maximisation of reward rate earned from service completions, net of the penalties paid whenever admission is denied, and the costs incurred upon every customer loss through impatience. We show that the system is indexable under mild conditions on model parameters and give an explicit construction of an index policy for admission control and routing founded on a proposal of Whittle for restless bandits. We are able to gain insights regarding the strength of performance of the index policy from the nature of solutions to the Lagrangian relaxation used to develop the indices. These insights are strengthened by the development of performance bounds. Although we are able to assert the optimality of the index heuristic in a range of asymptotic regimes, the performance bounds are also able to identify instances where its performance is relatively weak. Numerical studies are used to illustrate and support the theoretical analyses.
Total ankle replacement in patients with significant pre-operative deformity of the hindfoot
Authors: Hobson S. A. , Karantana A. , Dhar S.
Published: March 2009

We carried out 123 consecutive total ankle replacements in 111 patients with a mean follow-up of four years (2 to 8). Patients with a hindfoot deformity of up to 10° (group A, 91 ankles) were compared with those with a deformity of 11° to 30° (group B, 32 ankles). There were 18 failures (14.6%), with no significant difference in survival between groups A and B. The clinical outcome as measured by the post-operative American Orthopaedic Foot and Ankle Surgeons score was significantly better in group B (p = 0.036). There was no difference between the groups regarding the post-operative range of movement and complications. Correction of the hindfoot deformity was achieved to within 5° of neutral in 27 ankles (84%) of group B patients. However, gross instability was the most common mode of failure in group B. This was not adequately corrected by reconstruction of the lateral ligament.

Total ankle replacement can safely be performed in patients with a hindfoot deformity of up to 30°. The importance of adequate correction of alignment and instability is highlighted.
Revision following cemented and uncemented primary total hip replacement
Authors: Hooper G. J. , Rothwell A. G. , Stringer M. , Frampton C.
Published: March 2009

We have reviewed the rate of revision of fully cemented, hybrid and uncemented primary total hip replacements (THRs) registered in the New Zealand Joint Registry between 1999 and December 2006 to determine whether there was any statistically significant difference in the early survival and reason for revision in these different types of fixation. The percentage rate of revision was calculated per 100 component years and compared with the reason for revision, the type of fixation and the age of the patients.

Of the 42 665 primary THRs registered, 920 (2.16%) underwent revision requiring change of at least one component. Fully-cemented THRs had a lower rate of revision when considering all causes for failure (p < 0.001), but below the age of 65 years uncemented THRs had a lower rate (p < 0.01). The rate of revision of the acetabular component for aseptic loosening was less in the uncemented and hybrid groups compared with that in the fully cemented group (p < 0.001), and the rate of revision of cemented and uncemented femoral components was similar, except in patients over 75 years of age in whom revision of cemented femoral components was significantly less frequent (p < 0.02). Revision for infection was more common in patients aged below 65 years and in cemented and hybrid THRs compared with cementless THRs (p < 0.001). Dislocation was the most common cause of revision for all types of fixation and was more frequent in both uncemented acetabular groups (p < 0.001). The experience of the surgeon did not affect the findings.

Although cemented THR had the lowest rate of revision for all causes in the short term (90 days), uncemented THR had the lowest rate of aseptic loosening in patients under 65 years of age and had rates comparable with international rates of aseptic loosening in those over 65 years.
The influence of the mechanical environment on remodelling of the patellar tendon
Authors: Rumian A. P. , Draper E. R. C. , Wallace A. L. , Goodship A. E.
Published: March 2009

An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons.

The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.
Osteochondral autologous transplantation for the treatment of full-thickness cartilage defects of the shoulder
Authors: Kircher J. , Patzer T. , Magosch P. , Lichtenberg S. , Habermeyer P.
Published: March 2009

We describe the outcome at a mean follow-up of 8.75 years (7.6 to 9.8) of seven patients who had undergone osteochondral autologous transplantation for full-thickness cartilage defects of the shoulder between 1998 and 2000. These patients have been described previously at a mean of 32.6 months when eight were included. One patient has been lost to follow-up. The outcome was assessed by the Constant shoulder score and the Lysholm knee score to assess any donor-site morbidity. Standard radiographs and MR scores were obtained and compared with the pre-operative findings and the results from the previous review.

No patient required any further surgery on the shoulder. The mean Constant score improved significantly until the final follow-up (p = 0.018). The Lysholm score remained excellent throughout. There was a significant progression of osteoarthritic changes from the initial surgery to the first and final follow-up but this did not appear to be related to the size of the defect, the number of cylinders required or the Constant score (p = 0.016). MRI showed that all except one patient had a congruent joint surface at the defect with full bony integration of all osteochondral cylinders.

The results have remained satisfactory over a longer period with very good objective and subjective findings.
The supination deformity and associated deformities of the upper limb in severe birth lesions of the brachial plexus
Authors: Yam A. , Fullilove S. , Sinisi M. , Fox M.
Published: March 2009

We reviewed 42 consecutive children with a supination deformity of the forearm complicating severe birth lesions of the brachial plexus.

The overall incidence over the study period was 6.9% (48 of 696). It was absent in those in Narakas group I (27.6) and occurred in 5.7% of group II (13 of 229), 9.6% of group III (11 of 114) and 23.4% of group IV (18 of 77).

Concurrent deformities at the shoulder, elbow, wrist and hand were always present because of muscular imbalance from poor recovery of C5 and C7, inconsistent recovery of C8 and T1 and good recovery of C6. Early surgical correction improved the function of the upper limb and hand, but there was a tendency to recurrence. Pronation osteotomy placed the hand in a functional position, and increased the arc of rotation of the forearm. The supination deformity recurred in 40% (17 of 42) of those treated by pronation osteotomy alone, probably because of remodelling of the growing bone.

Children should be followed up until skeletal maturity, and the parents counselled on the likelihood of multiple operations.
A Behavioral Genetic Study of the Dark Triad of Personality and Moral Development
Authors: Campbell Jennifer , Schermer Julie Aitken , Villani Vanessa C. , Nguyen Brenda , Vickers Leanne , Vernon Philip A.
Published: March 2009

The present study is the first behavioral genetic investigation of relationships between the Dark Triad of personality — Machiavellianism, narcissism, and subclinical psychopathy — and moral development. Participants were 154 monozygotic twin pairs and 82 same-sex dizygotic twin pairs. Higher scores on Machiavellianism and psychopathy were positively correlated with low levels of moral development; high psychopathy scores also correlated negatively with high levels of moral development. Individual differences in lower levels of moral development were attributable to genetic and nonshared environmental factors but, very interestingly, individual differences in the highest levels of moral development showed no genetic basis but were entirely attributable to shared and nonshared environmental factors. Finally, correlations between the Dark Triad and moral development variables showed no genetic basis while correlations among the moral development variables were variously attributable to correlated genetic and correlated environmental factors.
The Norwegian Institute of Public Health Twin Study of Mental Health: Examining Recruitment and Attrition Bias
Authors: Tambs Kristian , Rønning Torbjørn , Prescott C. A. , Kendler Kenneth S. , Reichborn-Kjennerud Ted , Torgersen Svenn , Harris Jennifer R.
Published: March 2009

All Norwegian twin pairs born 1967–1974 and still living in Norway in 1992 were invited to a health questionnaire study (Q1). 2,570 pairs (65%) participated. These cohorts and the twin cohorts born 1967–1979 were invited to a new questionnaire study (Q2) in 1998. This time 3,334 pairs (53%) participated. Almost all pairs having participated in the 1998 study were invited to an interview study of mental health (MHS), taking place 1999–2004. 1,391 complete pairs (44%) participated. The questionnaire studies included extensive data on somatic health with fewer items on mental health and demography. Health-related and demographic information available from the Medical Birth Registry on all invited twins was applied to predict participation to the first study. A few registry variables indicating poor health predicted nonparticipation in Q1. Health information and demography from Q1 were tested as predictors of participation in the follow-up study (Q2). Monozygosity, female sex, being unmarried, having no children, and high education predicted participation, whereas few indicators of poor mental and somatic health and unhealthy lifestyle moderately predicted nonparticipation in Q2. No health indicators reported in Q2 predicted further participation. Standard genetic twin analyses of indicators of various mental disorders from Q2, validated by diagnostic data from the MHS, did not indicate differences in genetic/environmental covariance structures between participants and nonparticipants in MHS. In general the results show a moderate selection towards good mental and somatic health. Attrition from Q2 to the MHS does not appear to affect twin analyses of mental health related variables.
American Girl and the Brand Gestalt: Closing the Loop on Sociocultural Branding Research
Authors: Diamond Nina , Sherry John F. , Muñiz Albert M. , McGrath Mary Ann , Kozinets Robert V. , Borghini Stefania
Published: March 2009

This article describes an investigation of the American Girl brand that provides a more complete and holistic understanding of sociocultural branding. Recent research on emotional branding, together with prior work on brands’ symbolic nature and their role as relationship partners, represents a significant shift in the way marketers think about brands and brand management. However, a full understanding of powerful and emotionally resonant brands has been elusive, in part because sociocultural branding knowledge has accumulated in a piecemeal way and lacks coherence and integrity. In addition, powerful brands are extraordinarily complex and multifaceted, but in general they have been studied from a single perspective in a single setting. On the basis of a qualitative exploration of the American Girl brand that is both deep and broad, the authors posit that an emotionally powerful brand is best understood as the product of a complex system, or gestalt, whose component parts are in continuous interplay and together constitute a whole greater than their sum. Studying American Girl from the perspectives of various stakeholder groups in many of the venues in which the brand is manifest, the authors attempt to close the sociocultural branding research loop and identify implications for brand management.
Retrodifferentiation – a mechanism for cellular regeneration?
Authors: Hass Ralf
Published: March 2009

Cellular differentiation can be characterized by the acquisition of specified properties during several steps of development whereby the original stem- or precursor-like populations can finally obtain a certain phenotype with highly specific cell functions. The continuing maturation process can be paralleled by progressively reduced proliferative capacity in various cell types functioning as postmitotic tissues. Conversely, other cell populations (e.g., distinct immune cells) may carry out their specific function upon stimulation of proliferation. While these differentiated phenotypes perform their appropriate specific duties throughout the functioning organism, nature may provide an interesting alternative within this concept of life: sometimes, differentiation steps appear to be reversible. Thus, retrograde differentiation – also termed retrodifferentiation – and accordingly rejuvenation may occur when differentiated cells lose their specific properties acquired during previous steps of maturation. Consequently, retrodifferentiation and rejuvenation could provide enormous potential for tissue repair and cell renewal; however, regulatory dysfunctions within these retrograde developments may also involve the risk of tumor promotion.
Management of the human mucosal defensive barrier: evidence for glycan legislation
Authors: Patsos Georgios , Corfield Anthony
Published: March 2009

The human gastrointestinal barrier comprises several layers which enable protection against the external environment. The mucosal epithelium, lamina propria, glycocalyx and secreted mucus each make a contribution to barrier protection. Glycocalyx and secreted mucins constitute a glycosylated environment which interacts with the enteric microflora. Turnover of the mucus layer and the creation of binding ligands for bacteria are significant factors in gut homeostasis. The gut microbiota is composed of many bacterial species, but improved technology has allowed detection of populations present at different stages of development and in disease. Interaction of the microflora with the gut occurs from birth onwards and enables maturation of gut angiogenesis and glycosylation as demonstrated in mouse models. Glycan legislation regulates the ongoing interaction between the microflora and the host mucosa. This accounts for host glycosylation mechanisms providing a dynamic response to fluctuations in the gut microflora. Evidence for glycan legislation is based on a surgical model where intact mucosa can be compared with and without contact to the faecal microflora. In addition, mucosal cell glycosylation is assessed using inhibitors of O-glycan synthesis. These inhibitors lead to growth arrest in cultured colorectal cancer cell lines through the induction of apoptosis and downregulation of proliferation.
Analysis of the Impact Performance of Ice Hockey Helmets Using Two Different Test Methodologies
Authors: Giacomazzi Amber , Smith Terry , Kersey Robert
Published: March 2009

This paper reports on the results of a study to determine the protective characteristics of ice hockey helmets when tested using two different methodologies. The first methodology involved a traditional monorail drop impact test commonly used in North American ice hockey helmet standards (i.e., ASTM F1045, CSA Z262.1). This involves a guided freefall test onto a flat anvil using an ISO headform fitted with a uniaxial accelerometer at its center of gravity. The second methodology involved striking a Hybrid III head and neck mounted to a linear bearing track with a pendulum impactor. The use of a linear bearing track permitted the Hybrid III headform to move freely following the initial impact. At the distal end of the pendulum, a flat steel anvil was used to represent the impacting object. This configuration was felt to represent a head check from an opposing player, believed to be one of the mechanisms of head injury in ice hockey. Linear and angular acceleration measurements were recorded for all pendulum tests. High speed video was used to capture all headform motion. A total of six different helmet models were evaluated using both test methodologies. Peak linear headform accelerations were compared between helmet models tested using the monorail drop system and the identical helmet model tested using the impact pendulum. The results showed significant differences between helmet models as well as between the two different test methodologies. The implications of these results relative to current ice hockey standards and relative to head injury in ice hockey are discussed.
Chapter 3 Electrical Breakdown in Dielectric Fluids
Authors: Forster EO
Published: March 2009

To start the discussion of the subject matter, it appears desirable to ascertain what is meant by dielectric fluids. Obviously there are many ways in which to classify materials which depend usually on their end use. Of interest here is the one which considers a material's resistance to the flow of electricity as a guide. For example, materials having a specific resistance of less than one microohm per centimeter are called conductors, those having less than one gigaohm per centimeter are called semiconductors, and those having higher resistivities are referred to as insulators or dielectric materials. It is this last group, that comprises in addition to fluids, solids, and gases, that is of interest here.
Chapter 4 Physical and Chemical Properties of Mineral Insulating Oils
Authors: Duval M , Rouse TO
Published: March 2009

Dielectric liquids are a major part of the electrical insulation system in many types of electrical equipment-transformers, circuit breakers, bushings, cables, and capacitors. Often the insulation liquid provides additional functions. It is also the cooling medium in transformers and cables, the arc extinguishing phase in switchgear, or even the lubricant in tap changers and circulating pumps. Each application then demands an insulating liquid with somewhat different electrical, chemical, and physical characteristics. In transformers, for example, the dielectric liquid must possess high specific heat and thermal conductivity along with low viscosity and pour point in order to provide effective heat transfer. Electrical stresses are not extremely high. However, these stresses are high in capacitors, and the dielectric liquid must provide exceptional resistance to partial electrical discharges (high discharge inception voltage, high gas adsorption). Less heat is generated in normal operation of a capacitor, and the physical characteristics of the liquid related to heat transfer are of lesser concern. Still another set of characteristics is required in circuit breakers. The electrical arc associated with operation must die abruptly as the breaker is opened or closed. The initial degradation in an arc in the liquid must not produce a situation in which the arc is sustained as the voltage across the liquid falls.
Chapter 5 Molecular Structure and Composition of Liquid Insulating Materials
Authors: Vincent GA
Published: March 2009

It is necessary to know something about the chemical bonding holding atoms together to form molecules and the interactions of molecules in order to have some understanding of matter. Why is a liquid a liquid and not a gas or a solid? What is the basis of the physical and chemical properties of liquids?
Chapter 1-Bone Grafts and Bone Graft Substitutes: A Brief History
Authors: Laurencin CT , Khan Y
Published: March 2009

THE ORIGIN OF THE FIELD OF MEDICINE as a formal discipline has been traced to Africa by many historians. Imhotep's descriptions of ailments and treatments were found written on papyrus and translated in the mid-1800s by Edwin Smith [1]. Among the medical descriptions included in Imhotep's writings are cervical dislocations, skull fractures, and compound fractures [1]. Indeed, mummies found in Egyptian tombs have been found with crude braces constructed from wood planks and linen straps on their limbs representing some of the earliest accounts of orthopedics [2]. The use of autografts, allografts, and bone graft substitutes has interesting origins as well. The use of each graft type dates back several hundred years to apparently crude yet inspired methods and theories, which nonetheless set the stage for what we today consider state-of-the-art. Below is a brief history of each graft sub-group.
Chapter 13-Bone Graft Substitutes: Basic Information for Successful Clinical Use with Special Focus on Synthetic Graft Substitutes
Authors: Agrawal M , Katti DS , Boyan BD , McMillan J , Lohmann CH , Ranly DM , Schwartz Z
Published: March 2009

BONE GRAFTING TECHNIQUES ARE USED in many fields of surgery including orthopedic and trauma surgery, periodontal surgery, and maxillofacial surgery. The need to replace bone lost in chronic disease, infection or trauma is clear, and the field has expanded considerably since substitutes were first used to supplement or replace autologous or allogeneic bone grafting. As a result, the number of choices continues to increase as new materials are developed. However, the rationale for selection of one material over another is not yet clear in many clinical situations. This is in part due to the lack of information on basic bone biology as it applies to implant materials in general, and to a particular clinical application. The purpose of this review is to introduce the variety of bone graft materials currently available, discuss some of the new materials under development, and provide a biological rationale for the outcome when these materials are used clinically in orthopedics.
Drosophila Transposon Insertions as Unknowns for Structured Inquiry Recombination Mapping Exercises in an Undergraduate Genetics Course
Authors: Marcus Jeffrey M , Hughes Tia M
Published: March 2009

Structured inquiry approaches, in which students receive a Drosophila strain of unknown genotype to analyze and map the constituent mutations, are a common feature of many genetics teaching laboratories. The required crosses frustrate many students because they are aware that they are participating in a fundamentally trivial exercise, as the map locations of the genes are already established and have been recalculated thousands of times by generations of students. We modified the traditional structured inquiry approach to include a novel research experience for the students in our undergraduate genetics laboratories. Students conducted crosses with Drosophila strains carrying P[lacW] transposon insertions in genes without documented recombination map positions, representing a large number of unique, but equivalent genetic unknowns. Using the eye color phenotypes associated with the inserts as visible markers, it is straightforward to calculate recombination map positions for the interrupted loci. Collectively, our students mapped 95 genetic loci on chromosomes 2 and 3. In most cases, the calculated 95% confidence interval for meiotic map location overlapped with the predicted map position based on cytology. The research experience evoked positive student responses and helped students better understand the nature of scientific research for little additional cost or instructor effort.
The Dot1 Histone Methyltransferase and the Rad9 Checkpoint Adaptor Contribute to Cohesin-Dependent Double-Strand Break Repair by Sister Chromatid Recombination in Saccharomyces cerevisiae
Authors: Conde Francisco , Refolio Esther , Cordón-Preciado Violeta , Cortés-Ledesma Felipe , Aragón Luis , Aguilera Andrés , San-Segundo Pedro A
Published: March 2009

Genomic integrity is threatened by multiple sources of DNA damage. DNA double-strand breaks (DSBs) are among the most dangerous types of DNA lesions and can be generated by endogenous or exogenous agents, but they can arise also during DNA replication. Sister chromatid recombination (SCR) is a key mechanism for the repair of DSBs generated during replication and it is fundamental for maintaining genomic stability. Proper repair relies on several factors, among which histone modifications play important roles in the response to DSBs. Here, we study the role of the histone H3K79 methyltransferase Dot1 in the repair by SCR of replication-dependent HO-induced DSBs, as a way to assess its function in homologous recombination. We show that Dot1, the Rad9 DNA damage checkpoint adaptor, and phosphorylation of histone H2A (γH2A) are required for efficient SCR. Moreover, we show that Dot1 and Rad9 promote DSB-induced loading of cohesin onto chromatin. We propose that recruitment of Rad9 to DSB sites mediated by γH2A and H3K79 methylation contributes to DSB repair via SCR by regulating cohesin binding to damage sites. Therefore, our results contribute to an understanding of how different chromatin modifications impinge on DNA repair mechanisms, which are fundamental for maintaining genomic stability.
Constructed Microhabitat Bundles for Sampling Fishes and Crayfishes in Coastal Plain Streams
Authors: Warren Melvin L. , Sheldon Andrew L. , Haag Wendell R.
Published: March 2009

We investigated fish and crayfish use of standardized, constructed microhabitats (bundles) in three northern Mississippi streams. Cypress Creek and the Little Tallahatchie Canal were channelized and incised and had little woody cover; Puskus Creek was unchannelized and unincised and had abundant woody cover. We constructed three types of bundles (cane, leaf, and string) and deployed replicates of each in winter and spring. Occupancy of bundles by fish and crayfish was high and included 32 fish species representing eight families. Fish abundance did not differ among bundle types or between channel positions (bank or midchannel), but abundance of crayfish showed mixed responses to bundle type and position. Fish and crayfish use of bundles was higher in the channelized streams (89% occupied) than in the unchannelized stream (49% occupied). Furthermore, after a winter storm, fish use increased in the channelized streams but not in the unchannelized stream. Bundles yielded abundance estimates with modest to poor precision (40–73% for fish; 37–125% for crayfish); about 110–140 bundles would be necessary to consistently achieve precision of 30%. Bundles were effective for sampling a subset of fish assemblages (e.g., darters Etheostoma spp. and Percina spp. and madtoms Noturus spp.), but other fish species were conspicuously underrepresented or absent in our samples relative to sampling by electrofishing and seine (e.g., open-water species and large individuals). Nevertheless, microhabitat bundles can be effective for sampling small fish and crayfish that associate with woody cover and that are difficult to sample with conventional methods.
A selective small molecule glucagon-like peptide-1 secretagogue acting via depolarization-coupled Ca2+ influx
Authors: Eiki Jun-ichi , Saeki Kaori , Nagano Norihiro , Iino Tomoharu , Yonemoto Mari , Takayenoki-Iino Yoko , Ito Satoru , Nishimura Teruyuki , Sato Yoshiyuki , Bamba Makoto , Watanabe Hitomi , Sasaki Kaori , Ohyama Sumika , Kanatani Akio , Nagase Toshio , Yada Toshihiko
Published: March 2009

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that potentiates insulin secretion in a glucose-dependent manner. Selective GLP-1 secretagogue would be one of the potential therapeutic targets for type 2 diabetes. Here, we describe a newly identified small molecule compound (compound A) that stimulates secretion of GLP-1 in murine enteroendocrine cell lines, STC-1 and GLUTag cells, and in primary cultured fetal rat intestinal cells (FRIC). The underlying mechanism by which compound A stimulated GLP-1 secretion was also examined. Compound A stimulated GLP-1 secretion from STC-1 cells in a concentration-dependent manner, and also from GLUTag cells and FRIC. The action of compound A was selective against other tested endocrine functions such as secretion of insulin from rat islets, growth hormone from rat pituitary gland cells, and norepinephrine from rat PC-12 cells. In STC-1 cells, the compound A-stimulated GLP-1 secretion was neither due to cyclic AMP production nor to Ca2+ release from intracellular stores, but to extracellular Ca2+ influx. The response was inhibited by the presence of either L-type Ca2+ channel blockers or K+ ionophore. Perforated-patch clamp study revealed that compound A induces membrane depolarization. These results suggest that neither Gαs- nor Gαq-coupled signaling account for the mechanism of action, but depolarization-coupled Ca2+ influx from extracellular space is the primary cause for the GLP-1 secretion stimulated by compound A. Identifying a specific target molecule for compound A will reveal a selective regulatory pathway that leads to depolarization-mediated GLP-1 secretion.
Inter‐cohort competition drives density dependence and selective mortality in a marine fish
Authors: Samhouri Jameal F. , Steele Mark A. , Forrester Graham E.
Published: March 2009

For organisms with complex life cycles, the transition between life stages and between habitats can act as a significant demographic and selective bottleneck. In particular, competition with older and larger conspecifics and heterospecifics may influence the number and characteristics of individuals successfully making the transition. We investigated whether the availability of enemy‐free space mediated the interaction between adult goldspot gobies (Gnatholepis thompsoni), a common tropical reef fish, and juvenile conspecifics that had recently settled from the plankton. We added rocks, which provide refuge from predators, to one‐half of each of five entire coral reefs in the Bahamas and measured the survival and growth of recent settlers in relation to adult goby densities. We also evaluated whether mortality was selective with respect to three larval traits (age at settlement, size at settlement, and presettlement growth rate) and measured the influence of refuge availability and adult goby density on selection intensity. Selective mortality was measured by comparing larval traits of newly settled gobies (≤5 d postsettlement) with those of survivors (2–3 week postsettlement juveniles). We detected a negative relationship between juvenile survival and adult goby density in both low‐ and high‐refuge habitats, though experimental refuge addition reduced the intensity of this density dependence. Juvenile growth also declined with increasing adult goby density, but this effect was similar in both low‐ and high‐refuge habitats. Refuge availability had no consistent effect on selective mortality, but adult goby density was significantly related to the intensity of size‐selective mortality: bigger juveniles were favored where adults were abundant, and smaller juveniles were favored where adults were rare. Given the typically large difference in sizes of juveniles and adults, similar stage‐structured interactions may be common but underappreciated in many marine species.
Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)
Authors: Newsome Seth D. , Tinker M. Tim , Monson Daniel H. , Oftedal Olav T. , Ralls Katherine , Staedler Michelle M. , Fogel Marilyn L. , Estes James A.
Published: March 2009

Differences in diet composition among conspecifics (dietary specialization) have been documented across a broad range of taxonomic groups and habitats, and such variation at the individual level is increasingly recognized as an important component of diversity in trophic interactions. Accurate identification of individual dietary specialization, however, requires longitudinal dietary records that are labor‐intensive and cost‐prohibitive to obtain for many species. Here we explore the use of stable isotopes (δ13C and δ15N) as a promising technique for detecting and quantifying patterns of individual dietary specialization. Southern sea otters (Enhydra lutris nereis) offer a unique opportunity for testing this approach because (1) they consume a wide variety of prey that span multiple trophic levels, habitats, and ecologically defined functional groups; and (2) individual diet specialization can be validated with existing observational data. We analyzed the isotopic composition of sea otter vibrissae (n = 31) in order to characterize inter‐ and intra‐individual variation in sea otter diets at Monterey Bay, California, USA. At the population level, sea otters showed substantial variation in both δ13C and δ15N values, occupying nearly all of the “isotopic space” created by the diversity of isotopic signatures of potential prey taxa. Most of the variation in sea otter vibrissae was accounted for by differences between individuals, with much less contributed by within‐individual variation. A majority of sea otters (∼80%) showed relatively little temporal variability in isotopic composition, suggesting that the proportional composition of most individuals' diets is relatively constant over time; a few individuals (∼20%) exhibited a high degree of intra‐vibrissa isotopic variability, suggesting seasonal shifts in diet composition. These results and our interpretation of them were supported by long‐term observational data on the diets of radio‐tagged sea otters from the same population (n = 23). Our results demonstrate that stable isotopes can provide an efficient tool for measuring individual‐ and population‐level dietary breadth and may be useful for studying populations where longitudinal data on individuals would otherwise be impossible to acquire. This will be critical for examining the causes and consequences of dietary variation within and among consumer populations, thereby improving our understanding of these important ecological and evolutionary processes at the community level.
The ecology of climate change and infectious diseases
Authors: Lafferty Kevin D.
Published: March 2009

The projected global increase in the distribution and prevalence of infectious diseases with climate change suggests a pending societal crisis. The subject is increasingly attracting the attention of health professionals and climate‐change scientists, particularly with respect to malaria and other vector‐transmitted human diseases. The result has been the emergence of a crisis discipline, reminiscent of the early phases of conservation biology. Latitudinal, altitudinal, seasonal, and interannual associations between climate and disease along with historical and experimental evidence suggest that climate, along with many other factors, can affect infectious diseases in a nonlinear fashion. However, although the globe is significantly warmer than it was a century ago, there is little evidence that climate change has already favored infectious diseases. While initial projections suggested dramatic future increases in the geographic range of infectious diseases, recent models predict range shifts in disease distributions, with little net increase in area. Many factors can affect infectious disease, and some may overshadow the effects of climate.