bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequential deposition and electroforming of metal–ceramic composites for thermal management applications
Authors: Olevsky E. A. , Wang X. , Ma J. , Maximenko A. , Stern M. B.
Published: January 2007

Three approaches for the fabrication of ceramic–metal composites for thermal management of electronic circuitry are studied both theoretically and experimentally. The first approach includes the fabrication of Cu/Al2O3 coatings by the sequential electrophoretic deposition (EPD) – electroplating method. The kinetics of EPD, suspension stability are analysed. The SEM characterisation of the produced deposits shows good bonding between Al2O3 inclusions and copper matrix. An alternative approach includes the electroforming of copper ‘rivets’ on plastic substrate and on a porous SiC skeleton. The residual stress distribution at the ceramic/metal interface was simulated using finite element analysis. The third approach involves the fabrication of metal–ceramic foams as a basis for integrated thermal sinks. Copper–silicon carbide foam is considered as a model and experimental system for this approach. The modelling results provide recommendations on the optimal thicknesses of the deposited ceramic and metal layers to achieve the best heat conductivity with minimal thermal expansion mismatch.
Effect of zinc–phosphate–molybdate conversion precoating on performance of cathode epoxy electrocoat on AZ91D alloy
Authors: Li G. Y. , Lian J. S. , Niu L. Y. , Jiang Z. H. , Dong H.
Published: January 2007

A new chromium free zinc–phosphate–molybdate composite conversion coating on AZ91D magnesium alloy has been developed using an acidic bath mainly containing zinc phosphate, sodium molybdate and sodium fluoride. The examinations of the microstructure and phase compositions reveal that the composite conversion coating is composed of nanocrystalline metallic Zn, Zn3(PO4)2.4H2O and MgMoO4. It has been found that the addition of molybdate in the conversion bath can refine the microstructure of the composite conversion coating and eliminate the formation of microcracks. Corrosion tests demonstrated that the zinc–phosphate–molybdate composite coating possesses a better corrosion resistance than conventional zinc–phosphate conversion coatings in 3%NaCl and NaOH (pH 13) solutions. This newly developed composite conversion coating has a low weight loss during electrocoating process and can effectively improve the adhesion and corrosion resistance of the electrocoat on AZ91D alloy.
Mouse preimplantation embryo responses to culture medium osmolarity include increased expression of CCM2 and p38 MAPK activation
Authors: Fong Barry , Watson Patricia H , Watson Andrew J
Published: January 2007

Background

Mechanisms that confer an ability to respond positively to environmental osmolarity are fundamental to ensuring embryo survival during the preimplantation period. Activation of p38 mitogen-activated protein kinase (MAPK) occurs following exposure to hyperosmotic treatment. Recently, a novel scaffolding protein called Osmosensing Scaffold for MEKK3 (OSM) was linked to p38 MAPK activation in response to sorbitol-induced hypertonicity. The human ortholog of OSM is cerebral cavernous malformation 2 (CCM2). The present study was conducted to investigate whether CCM2 is expressed during mouse preimplantation development and to determine whether this scaffolding protein is associated with p38 MAPK activation following exposure of preimplantation embryos to hyperosmotic environments.

Results

Our results indicate thatCcm2along with upstream p38 MAPK pathway constituents (Map3k3,Map2k3,Map2k6,and Map2k4) are expressed throughout mouse preimplantation development. CCM2, MAP3K3 and the phosphorylated forms of MAP2K3/MAP2K6 and MAP2K4 were also detected throughout preimplantation development. Embryo culture in hyperosmotic media increased p38 MAPK activity in conjunction with elevated CCM2 levels.

Conclusion

These results define the expression of upstream activators of p38 MAPK during preimplantation development and indicate that embryo responses to hyperosmotic environments include elevation of CCM2 and activation of p38 MAPK.
Molecular analysis of hepatitis B virus "a" determinant in asymptomatic and symptomatic Mexican carriers
Authors: Ruiz-Tachiquín Martha-Eugenia , Valdez-Salazar Hilda-Alicia , Juárez-Barreto Vicencio , Dehesa-Violante Margarita , Torres Javier , Muñoz-Hernández Onofre , Alvarez-Muñoz Ma-Teresa
Published: January 2007

Background

Hepatitis B virus (HBV) is a small DNA-containing virus with 4 genes, C, S, X and P. The S gene codes for the surface antigen (HBsAg), which contains the "a" determinant, the main region for induction of a protective humoral immune response. To compare the genotype and sequence of the "a" determinant between strains isolated from asymptomatic and symptomatic Mexican HBV carriers.

Results

21 asymptomatic (blood donors) and 12 symptomatic (with clinical signs and with >1 year lamivudine treatment) HBV carriers were studied; all patients were positive for the HBsAg in serum. Viral load, genotypes, and subtypes were determined in plasma. A fragment of the S gene including the "a" determinant was PCR amplified and sequenced to determine genotype, subtype and to identify mutations. Mean viral load was 0.7965 × 104 copies/ml in asymptomatic carriers and 2.73 × 106 copies/ml in symptomatic patients. Genotypes H, C, and F were identified in asymptomatic individuals; whereas H was dominant in symptomatic patients. A fragment of 279 bp containing the "a" determinant was amplified from all 33 carriers and sequences aligned with S gene sequences in the GenBank. Mutations identified were Y100N, T126I, Q129H and N146K in the asymptomatic group, and F93I and A128V in the symptomatic group.

Conclusion

Differences in genotype and in mutations in the "a" determinant were found between strains from asymptomatic and symptomatic HBV Mexican carriers.
Pivotal Advance: CTLA-4+ T cells exhibit normal antiviral functions during acute viral infection
Authors: Raué Hans-Peter , Slifka Mark K
Published: January 2007

Previous studies have shown that T cells, which are genetically deficient in CTLA-4/CD152 expression, will proliferate uncontrollably, resulting in lethal autoimmune disease. This and other evidence indicate that CTLA-4 plays a critical role in the negative regulation of effector T cell function. In contrast to expectations, BrdU incorporation experiments demonstrated that CTLA-4 expression was associated with normal or even enhanced in vivo proliferation of virus-specific CD4+ and CD8+ T cells following acute lymphocytic choriomeningitis virus or vaccinia virus infection. When compared with CTLA-4– T cells directly ex vivo, CTLA-4+ T cells also exhibited normal antiviral effector functions following stimulation with peptide-coated cells, virus-infected cells, plate-bound anti-CD3/anti-CTLA-4, or the cytokines IL-12 and IL-18. Together, this indicates that CTLA-4 does not directly inhibit antivral T cell expansion or T cell effector functions, at least not under the normal physiological conditions associated with either of these two acute viral infections.
Improved parameterization to invert Rayleigh-wave data for shallow profiles containing stiff inclusions
Authors: Calderón-Macías Carlos , Luke Barbara
Published: January 2007

Inversion of shear-wave velocity profiles from phase-velocity measurements of Rayleigh-wave energy for sites containing stiff layers can be erroneous if such layers are not characterized in the starting or reference model. Incorporation of a priori knowledge then is key for converging upon a realistic or meaningful solution. Resolving soil profiles in desert regions where stiff layers cemented with calcium carbonate are intermixed with softer, uncemented media is an application for which locating shallow stiff inclusions has important implications. Identification of the stiff layers is critical for foundation design and cost estimating of excavations. A parameterization that seems adequate for this problem is to solve for anticipated high-stiffness layers embedded in a coarser (background) profile that captures the general shear-wave velocity trend of the study area. The optimization is accomplished by using simulated annealing. Uncertainty measures resulting from the inversion are helpful for describing the influence of the parameterization on final model estimates.
Amplitude-variation-with-offset, elastic-impedence, and wave-equation synthetics — A modeling study
Authors: Mallick Subhashis
Published: January 2007

Amplitude-variation-with-offset (AVO) and elastic-impedance (EI) analysis use an approximate plane P-wave reflection coefficient as a function of angle of incidence. AVO and EI both can be used in a three-term or a two-term formulation. This study uses synthetic data to demonstrate that the P-wave primary reflections at large offsets can be contaminated by reflections from other wave modes that can affect the quality of three-term AVO or EI results. The coupling of P-waves and S-waves in seismic-wave propagation through finely layered media generates the interfering wave modes. A methodology such as prestack-wave-equation modeling can properly account for these coupling effects. Both AVO and EI also assume a convolutional model whose accuracy decreases as incidence angles increase. On the other hand, wave-equation modeling is based on the rigorous solution to the wave equation and is valid for any incidence angle. Because wave interference is minimal at small angles, a two-term AVO/EI analysis that restricts input from small angles is likely to give more reliable parameter estimates than a three-term analysis. A three-term AVO/EI analysis should be used with caution and should be calibrated against well data and other data before being used for quantitative analysis.
A homotopy method for well-log constraint waveform inversion
Authors: Han Bo , Fu Hongsun , Liu Hong
Published: January 2007

The primary difficulty posed by the method of waveform inversion for the acoustic-wave equation is the presence of local minima of the objective function. Waveform inversion fails to converge to the global minimum unless the wavefield contains very low frequencies, or the starting model is very close to the true model. Constraints can improve the convergence of the method; however, if the starting model is far from the correct model, normal iterative methods will still get trapped in local minima. We designed a homotopy method to improve the robustness of waveform inversion; it makes natural use of constraints, such as well logs. In addition, to further condition the inverse problem, we incorporate standard Tikhonov regularization. We demonstrate through a synthetic example that our method is more likely to find a global minimum than normal iterative methods.
Nonlinear process control of wave-equation inversion and its application in the detection of gas
Authors: Shi Yumei , Zhao Wenzhi , Cao Hong
Published: January 2007

The wave equation describes how seismic waves propagate in the subsurface. Inversion methods based on the wave equation naturally take into account the complex behavior of propagating waves and can be used to make accurate estimates of model parameters. However, computational cost and poor convergence have not been overcome, and thus restrict the broad application of this technique. Preconditioned conjugate gradient inversion using back-propagation techniques is a simple, robust implementation of wave-equation inversion in which the step length for correcting the model for each iteration is a crucial factor affecting convergence and hence computational cost. The step length can be calculated by an adaptive controller based on the theory of model reference nonlinear control that ensures that the error energy of the complex system vanishes rapidly. Although the computational cost for each iteration remains the same, the inversion is robust and converges more rapidly than other methods. We tested our method on synthetic data generated from a three-layer fractured model. The inversion converges to the true model after five iterations, and different initial models give similar inversion results. The application to 2D real data from a gas field in western China illustrates that even two iterations yield unambiguous interpretable inversion sections.
A 2D numerical study of the effect of particle shape and orientation on resistivity in shallow formations
Authors: Rey Etienne , Jongmans Denis
Published: January 2007

Surficial heterogeneous soils such as till, alluvial fans, or slope deposits are difficult to characterize by geotechnical tests because of the presence of decimeter- to meter-sized pebbles or rocks. The effective resistivity of such two-component media composed of a percentage of resistive particles embedded in a conductive matrix is given by the Bussian’s equation. The application of this equation allows the concentration of resistive particles to be determined if the resistivity values of each component and of the mixture, as well as the cementation exponent [Formula: see text], are known. However, previous theoretical and experimental studies have shown that the effective resistivity is affected by the shape of the particles. The objective of this study is to numerically determine the 2D effects of particle shape and orientation on the resistivity. Two configurations have been considered in the finite element (FE) modeling: laboratory-like measurements and field layout. For circular particles, the numerical results fit the Bussian’s equation with an exponent [Formula: see text] of 2. Aligned elongated particles induce an anisotropy which can raise or diminish the exponent [Formula: see text], depending on the particle orientation and the tortuosity of the current paths. Field experiment simulations showed that [Formula: see text] varies between 2.5 and 3.1 for an aspect ratio of 5 and that anisotropy resulting from the particle shape has little effect ([Formula: see text] close to 2) when this ratio is lower than 2.5. This increase of [Formula: see text] with the aspect ratio is in agreement with both theoretical models and experimental studies. For laboratory measurement simulations, [Formula: see text] values vary between 1.3 and 4 for a particle aspect ratio of 5, whatever the resistivity contrast between the particles and the matrix. The difference in results between the two configurations is explained by the paradox of anisotropy.
Magnetotelluric static shift: Estimation and removal using the cokriging method
Authors: Tournerie Benoit , Chouteau Michel , Marcotte Denis
Published: January 2007

We present and test a new method to correct for the static shift affecting magnetotelluric (MT) apparent resistivity sounding curves. We use geostatistical analysis of apparent resistivity and phase data for selected periods. For each period, we first estimate and model the experimental variograms and cross variogram between phase and apparent resistivity. We then use the geostatistical model to estimate, by cokriging, the corrected apparent resistivities using the measured phases and apparent resistivities. The static shift factor is obtained as the difference between the logarithm of the corrected and measured apparent resistivities. We retain as final static shift estimates the ones for the period displaying the best correlation with the estimates at all periods. We present a 3D synthetic case study showing that the static shift is retrieved quite precisely when the static shift factors are uniformly distributed around zero. If the static shift distribution has a nonzero mean, we obtained best results when an apparent resistivity data subset can be identified a priori as unaffected by static shift and cokriging is done using only this subset. The method has been successfully tested on the synthetic COPROD-2S2 2D MT data set and on a 3D-survey data set from Las Cañadas Caldera (Tenerife, Canary Islands) severely affected by static shift.
European Perspective on the Costs and Cost-Effectiveness of Cancer Therapies
Authors: Drummond Michael F. , Mason Anne R.
Published: January 2007

In Europe, the vast majority of the costs of cancer therapy fall on third-party payers, normally the government, or sickness funds. Therefore, the main focus of cost-effectiveness studies is to assist payers in deciding whether new therapies are worthwhile, despite their high cost. Drug budgets are regulated in most European countries. The main form of central control is price setting, with some form of reference pricing being the most common approach. This sets the price of drugs, either to an international standard, or to a common price for drugs in the same group or cluster. At the hospital level, the main control over cancer drugs is the hospital formulary. Studies have shown a wide variation among European countries in access to cancer drugs. Explanations for these variations include differences in research funding, the drug approval process, the role of health economics in decision making, and budgetary issues. Several countries in Europe now require economic data in making decisions about the reimbursement of new drugs. An examination of decisions made by the National Institute for Health and Clinical Excellence in the United Kingdom suggests that cancer drugs have fared quite well, with most recommendations being positive. This could be because of the seriousness of the health condition and the lack of alternative therapies for some cancer patients. If the policy of requesting cost-effectiveness evidence for pricing and reimbursement decisions becomes more popular, a major implication for the pharmaceutical industry is that studies should be conducted during phase III of clinical development to generate the required data.
Cost of Cancer Care: The Patient Perspective
Authors: Kim Paula
Published: January 2007

The diagnosis of cancer, along with subsequent related care, imposes a number of burdens on patients—physical, emotional, and financial. The financial expenses incurred extend well beyond the cost of medication, surgery, and related treatments. While these important issues warrant attention, patients also need assistance dealing with the indirect costs of cancer care, such as transportation, child care, and lost wages. There is an urgent need to improve the current inconsistent—sometimes nonexistent—methods used to inform patients about costs of cancer care as well as to provide them with appropriate assistance managing the costs and overall burden of cancer. Health care providers, patient advocates, agencies, and insurers have the responsibility and opportunity to provide leadership in this process. Most importantly, limited ability to address any of the expenses brought on by cancer should not prevent any patient from receiving necessary care.
Use of Modeling to Evaluate the Cost-Effectiveness of Cancer Screening Programs
Authors: Knudsen Amy B. , McMahon Pamela M. , Gazelle G. Scott
Published: January 2007

Cost-effectiveness analysis (CEA) is an analytic tool that provides a framework for comparing the health benefits and resource expenditures associated with competing medical and public health interventions, thereby allowing decision makers to identify interventions that yield the greatest amount of health, given their resource constraints. Models are important components of most, if not all, CEAs, and they play a key role in evaluating the cost-effectiveness of cancer screening programs, in particular. In this article, we describe the basic types of models used to evaluate cancer screening programs and provide examples of the use of models in CEAs and to guide cancer screening policy. Finally, we offer some suggestions for important concepts to consider when interpreting model results.
Value of High-Cost Cancer Care: A Behavioral Science Perspective
Authors: Weinfurt Kevin P.
Published: January 2007

Concerns about the high costs of cancer care have led to a renewed interest in understanding how patients value the outcomes of care. Psychologists, economists, and others have highlighted some of the ways in which patients and caregivers perceive and make treatment decisions. Prospect theory is the predominant framework for understanding decisions made in situations where the outcomes of each choice are uncertain. Prospect theory assumes that a patient values the outcomes of care not in absolute terms, such as years of life saved, but as deviations from the patient's point of reference. This article discusses some of the implications of this notion, along with discussing differences among people in their reference points. These and other considerations from the psychology of decision making help to clarify why some patients might be inclined to seek expensive or risky treatments in the hopes of achieving benefits that others might consider not worthwhile. An appreciation of these psychological issues might improve the quality of debates concerning the rising costs of cancer care.
Medical Oncologists' Views on Communicating With Patients About Chemotherapy Costs: A Pilot Survey
Authors: Schrag Deborah , Hanger Morgan
Published: January 2007

Purpose

As chemotherapy costs escalate, financial concerns have become relevant for more cancer patients. Yet, little is known about how oncologists communicate with patients about coping with chemotherapy treatment costs.

Methods

To understand how medical oncologists view these issues, we developed a survey eliciting their attitudes and behaviors surrounding discussing costs of therapy in the context of treatment decision making. The survey was piloted at a national meeting and then mailed to a random sample of actively practicing 2005 American Society of Clinical Oncology members in the 50 United States. Survey items used a 5-point Likert scale designed to elicit oncologists' practices and attitudes regarding discussion of chemotherapy costs with patients. The first survey wave also included two clinical vignettes about hypothetical patients contemplating treatment with high-cost regimens.

Results

Of 530 mailed surveys, 167 were returned for an overall response rate of 31.5%. Most oncologists reported knowledge of their patients' financial well-being: 15% all of the time, 39% most of the time, 33% some of the time, and 13% rarely/none of the time. There was substantial variation in oncologists' attitudes toward discussing chemotherapy costs with patients: 42% did so always or most of the time, 32% sometimes did, and 26% rarely or never did. Most oncologists (80%) felt that it was important to be explicit about the impact of treatment choices on patients' finances. However, 20% maintained that costs play no role in clinical encounters, and 31% reported a high degree of discomfort in discussing costs with patients. Referral to support staff for these discussions was common. Only a few oncologists (16%) acknowledged omitting treatment options on the basis of their perceptions of patients' ability to afford treatment.

Conclusion

There is important heterogeneity in medical oncologists' attitudes toward discussing chemotherapy treatment costs with patients. Mismatch between physician and patient viewpoints has the potential to result in miscommunication and suboptimally informed treatment decisions.
Cost of Cancer Care: Issues and Implications
Authors: Meropol Neal J. , Schulman Kevin A.
Published: January 2007

Medical technology is increasingly costly in most fields of clinical medicine. Oncology has not been spared from issues related to cost, in part resulting from the tremendous scientific progress that has lead to new tools for diagnosis, treatment, and follow-up of our patients. The increasing cost of health care in general (and cancer care in particular) raises complex questions related to its effects on our economy and the citizens of our society. This article reviews the macroeconomic principles and individual behaviors that govern medical spending, and examines how cost disproportionately affects various populations. Our overall goal is to frame debate about health policy concerns that influence the clinical practice of oncology.
The Sins of the Fathers: Franciscan Friars, Parish Priests, and the Sexual Conquest of the Yucatec Maya, 1545-1808
Authors: Chuchiak John F.
Published: January 2007

Differing from the rapid political, economic, and social conquests, the conquest of indigenous sexuality was often a long and deeply contested arena of indigenous-Spanish encounters. The roots of what can be called the “sexual conquest” of the Yucatec Maya began with the initial missions of the Franciscan friars. The earliest friars produced vocabularies, grammars, sermons, and confession manuals as tools for their missionary effort. By analyzing these missionary creations, we can approach an understanding of the friars' views of Maya sexuality. The Maya, however, often took the missionary teachings concerning proper and improper sexual activities, and through the lens of their own cultural concepts of sexuality and sexual relations they manipulated them for their own purposes. This paper will examine how the knowledge of the “sins of the fathers” served both the missionaries and the Maya in their struggle for control over the complex nature of evolving colonial sexuality.
“That Monster of Nature”: Gender, Sexuality, and the Medicalization of a “Hermaphrodite” in Late Colonial Guatemala
Authors: Few Martha
Published: January 2007

In Guatemala City in 1803, the court of the Royal Protomedicato requested that the physician Narciso Esparragosa examine Juana Aguilar, called by the court a “suspected hermaphrodite,” as part of the legal proceedings against her for double concubinage with men and women. This essay considers Esparragosa's report on Aguilar's sexual ambiguity and his efforts to classify her. The first section analyzes the scope and purpose of the report and places Esparragosa's anatomical and physiological assertions within the context of Enlightenment-era understandings of sexuality and sexual difference. The second section traces how Esparragosa built the argument that led him to classify Aguilar and her ambiguous sexuality into a separate category of “neither man nor woman.” Throughout his medical report, Esparragosa appropriated the language of monstrosity to underpin his characterization of Aguilar's sexual and physical difference, recast in gendered and racialized terms. He used these assertions to make certain claims of categorization that attempted to naturalize the female genitalia and to argue that female anatomical and physiological ambiguity led to sexual deviance.
How is pluripotency determined and maintained?
Authors: Niwa Hitoshi
Published: January 2007

Mouse embryonic stem (ES) cells are pluripotent, as they have the ability to differentiate into the various cell types of a vertebrate embryo. Pluripotency is a property of the inner cell mass (ICM), from which mouse ES cells are derived, and of the epiblast of the blastocyst. Recent extensive molecular studies of mouse ES cells have revealed the unique molecular mechanisms that govern pluripotency. These studies show that ES cells continue to self-renew because of a self-organizing network of transcription factors that prevents their differentiation and promotes their proliferation, and because of epigenetic processes that might be under the control of the pluripotent transcription factor network.
Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus)
Authors: Gheshmy Afshan , Anari Ali , Besada Donela , Reid Stephen G.
Published: January 2007

The goal of this study was to examine the role of respiratory-related afferent input on the chronic hypercapnia (CHC)-induced increase in central respiratory-related pH/CO2 chemosensitivity in cane toads (Bufo marinus). Toads were exposed to CHC (3.5% CO2) for 10 days,following which in vitro brainstem-spinal cord preparations were used to assess central respiratory-related pH/CO2 chemosensitivity. Motor output from the vagus nerve root was used as an index of breathing(fictive breathing). Olfactory denervation (OD), prior to exposure to CHC, was used to remove the influence of CO2-sensitive olfactory chemoreceptors, which inhibit breathing. Exposure to chronic hyperoxic hypercapnia (CHH) was used to reduce the level of arterial chemoreceptor input compared with CHC alone. In vivo experiments examined the effects of CHC, CHH and OD on the acute hypercapnic ventilatory response of intact animals. In vitro, a reduction in artifical cerebral spinal fluid(aCSF) pH increased fictive breathing in preparations taken from control and CHC animals. CHC caused an increase in fictive breathing compared with controls. OD and CHH abolished the CHC-induced augmentation of fictive breathing. In vivo, CHC did not cause an augmentation of the acute hypercapnic ventilatory response. CHH reduced the in vivo acute hypercapnic ventilatory response compared with animals exposed to CHC. In vivo, OD reduced breathing frequency and increased breath amplitude in both control and CHC animals. The results suggest that afferent input from olfactory and arterial chemoreceptors, during CHC, is involved in triggering the CHC-induced increase in central respiratory-related pH/CO2chemosensitivity.
Gait characterisation and classification in horses
Authors: Robilliard Justine J. , Pfau Thilo , Wilson Alan M.
Published: January 2007

Although a large number of foot-fall sequences are possible in quadrupeds,few sequences are routinely used. The aim of this paper is to characterise, by foot-fall pattern, the gaits used by horses and develop a novel technique to classify symmetric and asymmetric gaits using one common criterion. To achieve this speed and relative foot-fall, timings of all four limbs of eight Icelandic horses were measured using accelerometers. Linear discriminant analysis (LDA) was performed to find criteria that are optimal for discriminating between the different gaits. This also allowed us to evaluate whether gaits should be considered a continuum or as discrete entities. Foot-fall timings (stance times, swing times, duty factors and stride frequencies) for walk, tolt, trot, pace, left canter, right canter, left gallop and right gallop during over-ground locomotion at a range of speeds are presented. In the gaits of walk, tolt, trot and pace, foot-fall timings were equal between left and right hindlimbs and forelimbs so these gaits can be considered as symmetrical. Differences in stance times and duty factors were observed between gaits but are unlikely to be of biological significance due to their similar magnitude and inconsistent relative trends. This implies that metabolics or peak limb forces derived from contact times are unlikely to be the principal driving factors in gait transition between walk, trot, pace,canters and gallops, although these factors may influence the use of tolt at the lower and higher speeds. Gaits did cluster in the LDA space and the running gaits (tolt, trot, pace, left and right canters and gallops) could be considered a kinematic continuum but the relative relationship with walk may be more complex. Thus, LDA analysis has enabled common criteria to be discovered to accurately classify equine gaits on the basis of foot-fall timings on a stride-by-stride basis.
Adaptive regulation of digestive performance in the genusPython
Authors: Ott Brian D. , Secor Stephen M.
Published: January 2007

The adaptive interplay between feeding habits and digestive physiology is demonstrated by the Burmese python, which in response to feeding infrequently has evolved the capacity to widely regulate gastrointestinal performance with feeding and fasting. To explore the generality of this physiological trait among pythons, we compared the postprandial responses of metabolism and both intestinal morphology and function among five members of the genus Python: P. brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. These infrequently feeding pythons inhabit Africa, southeast Asia and Indonesia and vary in body shape from short and stout (P. brongersmai) to long and slender (P. reticulatus). Following the consumption of rodent meals equaling 25% of snake body mass, metabolic rates of pythons peaked at 1.5 days at levels 9.9-to 14.5-fold of standard metabolic rates before returning to prefeeding rates by day 6-8. Specific dynamic action of these meals (317-347 kJ) did not differ among species and equaled 23-27% of the ingested energy. For each species,feeding triggered significant upregulation of intestinal nutrient transport and aminopeptidase-N activity. Concurrently, intestinal mass doubled on average for the five species, in part due to an 85% increase in mucosal thickness, itself a product of 27-59% increases in enterocyte volume. The integrative response of intestinal functional upregulation and tissue hypertrophy enables each of these five python species, regardless of body shape, to modulate intestinal performance to meet the demands of their large infrequent meals.
Going wild: what a global small-animal tracking system could do for experimental biologists
Authors: Wikelski Martin , Kays Roland W. , Kasdin N. Jeremy , Thorup Kasper , Smith James A. , Swenson George W.
Published: January 2007

Tracking animals over large temporal and spatial scales has revealed invaluable and spectacular biological information, particularly when the paths and fates of individuals can be monitored on a global scale. However, only large animals (greater than ∼300 g) currently can be followed globally because of power and size constraints on the tracking devices. And yet the vast majority of animals is small. Tracking small animals is important because they are often part of evolutionary and ecological experiments, they provide important ecosystem services and they are of conservation concern or pose harm to human health. Here, we propose a small-animal satellite tracking system that would enable the global monitoring of animals down to the size of the smallest birds, mammals (bats), marine life and eventually large insects. To create the scientific framework necessary for such a global project, we formed the ICARUS initiative(www.IcarusInitiative.org),the International Cooperation for Animal Research Using Space. ICARUS also highlights how small-animal tracking could address some of the `Grand Challenges in Environmental Sciences' identified by the US National Academy of Sciences, such as the spread of infectious diseases or the relationship between biological diversity and ecosystem functioning. Small-animal tracking would allow the quantitative assessment of dispersal and migration in natural populations and thus help solve enigmas regarding population dynamics,extinctions and invasions. Experimental biologists may find a global small-animal tracking system helpful in testing, validating and expanding laboratory-derived discoveries in wild, natural populations. We suggest that the relatively modest investment into a global small-animal tracking system will pay off by providing unprecedented insights into both basic and applied nature.

Tracking small animals over large spatial and temporal scales could prove to be one of the most powerful techniques of the early 21st century, offering potential solutions to a wide range of biological and societal questions that date back two millennia to the Greek philosopher Aristotle's enigma about songbird migration. Several of the more recent Grand Challenges in Environmental Sciences, such as the regulation and functional consequences of biological diversity or the surveillance of the population ecology of zoonotic hosts, pathogens or vectors, could also be addressed by a global small-animal tracking system.

Our discussion is intended to contribute to an emerging groundswell of scientific support to make such a new technological system happen.
Growing out of a caste - reproduction and the making of the queen mole-rat
Authors: Henry Erin C. , Dengler-Crish Christine M. , Catania Kenneth C.
Published: January 2007

Naked mole-rats have a eusocial colony structure consisting of non-reproductive workers and a reproductively active caste where a single,dominant queen and 1-3 males produce all of the offspring. Well-established queens have elongated bodies that characterize their caste. Worker females retain the ability to transform into queens, however the trigger and time course for this physical transformation remain a mystery. Here, we show a direct link between periods of pregnancy and vertebral lengthening in nascent queens. Adult female mole-rats were paired with a male and radiographed weekly for two and a half years to track the growth of the lumbar vertebrae as the mole-rats became sexually mature and experienced pregnancies. The lumbar vertebrae of breeding females grew at an increased rate during each pregnancy but growth rates returned to normal between pregnancies and during extended periods without reproduction. The rate of lumbar lengthening was reduced to normal rates in older, established queens experiencing pregnancies. Our results imply that the length of a new queen mole-rat is proportional to the number of pregnancies experienced and suggest that hormones related to pregnancy may play the critical role in bone growth associated with caste transformation.
Quantitative analysis of tethered and free-swimming copepodid flow fields
Authors: Catton Kimberly B. , Webster Donald R. , Brown Jason , Yen Jeannette
Published: January 2007

We quantified the flow field generated by tethered and free-swimming Euchaeta antarctica using the particle image velocimetry (PIV)technique. The streamlines around the free-swimming specimens were generally parallel to the body axis, whereas the streamlines around all of the tethered copepodids demonstrated increased curvature. Differences noted in the streamline pattern, and hence the vorticity, dissipation rate and strain rate fields, are explained by considering the forces on the free-swimming specimen compared to the tethered specimen. Viscous flow theory demonstrates that the force on the fluid due to the presence of the tether irrevocably modifies the flow field in a manner that is consistent with the measurements. Hence,analysis of the flow field and all associated calculations differ for tethered versus free-swimming conditions. Consideration of the flow field of the free-swimming predatory copepodid shows the intensity of the biologically generated flow and the extent of the mechanoreceptive signal quantified in terms of shear strain rate. The area in the dorso-ventral view surrounded by the 0.5 s-1 contour of exy, which is a likely threshold to induce an escape response, is 11 times the area of the exoskeletal form for the free-swimming case. Thus, mechanoreceptive predators will perceive a more spatially extended signal than the body size.
The energetic consequence of specific dynamic action in southern bluefin tunaThunnus maccoyii
Authors: Fitzgibbon Q. P. , Seymour R. S. , Ellis D. , Buchanan J.
Published: January 2007

The effect of feeding on the rate of oxygen consumption(ṀO2) of four groups of three southern bluefin tuna Thunnus maccoyii (SBT) was examined in a large static respirometer at water temperatures of 18.2-20.3°C. Six feeding events of rations between 2.1-8.5% body mass(%Mb) of Australian sardines (Sardinops neopilchardus) were recorded (two of the groups were fed twice). Before feeding, fish swam between 0.71 and 1.4 body lengths s-1(BL s-1) and the routine metabolic rate (RMR) was 366±32.5 mg kg-1 h-1 (mean ± s.e.m.). For all trials, ṀO2was elevated post feeding, presumably as a result of specific dynamic action(SDA). Swimming velocity was also elevated post feeding for periods similar to that of ṀO2(between 20-45 h, longest for the largest rations). Post feeding swimming velocity increased to between 0.87-2.6 BL s-1 and was also dependent on ration consumed. It is suggested that the purpose of increased post-feeding swimming velocity was to increase ventilation volume as a response to the enhanced metabolic demand associated with SDA. Peak post-prandial ṀO2increased linearly with ration size to a maximum of 1290 mg kg-1h-1, corresponding to 2.8 times the RMR. When converted to its energy equivalent, total magnitude of SDA was linearly correlated with ration size to a maximum of 192 kJ kg-1 h-1, and as a proportion of gross energy ingested (SDA coefficient), it averaged 35±2.2%. These results demonstrate that, although the factorial increase of SDA in SBT is similar to that of other fish species, the absolute energetic cost of SDA is much higher. These results support the contention that tuna are energy speculators, gambling high rates of energy expenditure for potentially higher rates of energy returns. The ration that southern bluefin tuna require to equal the combined metabolic costs of SDA and RMR is estimated in this study to be 3.5%Mb of Australian sardines per day.
Ground forces applied by galloping dogs
Authors: Walter Rebecca M. , Carrier David R.
Published: January 2007

The gallop differs from most other quadrupedal gaits in that each limb plays a unique role. This study compares the ground forces applied by the four limbs and uses force differences between limbs to address the question of why the gallop is the fastest quadrupedal gait. Individual ground forces were recorded from each of the four limbs as six dogs galloped down a runway at constant speed. Trials were videotaped at high speed using a camera positioned perpendicular to the runway, and velocity was measured using photosensors. The trailing forelimb applied greater peak vertical forces than the lead forelimb,however the vertical impulses from the two forelimbs were similar because the lead forelimb had a longer contact interval. The trailing forelimb and lead hindlimb applied greater peak accelerating forces and accelerating force impulses than their contralateral limbs despite their tendency to have shorter contact intervals. The accelerating impulse of both forelimbs combined did not differ significantly from that of both hindlimbs. The forelimbs applied a greater decelerating impulse than the hindlimbs, such that their net fore-aft impulse was decelerating whereas that of the hindlimbs was accelerating. The greater accelerating impulse applied by the trailing forelimb and greater decelerating impulse applied by the lead forelimb are consistent with the forelimbs acting as elastic struts rather than being actively retracted. In contrast, greater accelerating forces were produced by the lead hindlimb while the center of mass was lifted, suggesting that the hindlimbs are more actively extended or retracted during stance. The differences in ground forces measured between paired limbs suggest that the lead forelimb and trailing hindlimb are limited in their ability to apply forces by their positions in the stride cycle rather than by their muscular capacity. Although a bound or half-bound would allow more limbs to produce their maximal forces, a gallop may generate higher speeds because it is more efficient. Galloping could be more efficient than other gaits involving sagittal bending if the increased number of ground contact intervals decreased either the decelerating forces applied at the onset of ground contact or the vertical motion of the center of mass.
The kinematics of multifunctionality: comparisons of biting and swallowing inAplysia californica
Authors: Neustadter David M. , Herman Robert L. , Drushel Richard F. , Chestek David W. , Chiel Hillel J.
Published: January 2007

What are the mechanisms of multifunctionality, i.e. the use of the same peripheral structures for multiple behaviors? We studied this question using the multifunctional feeding apparatus of the marine mollusk Aplysia californica, in which the same muscles mediate biting (an attempt to grasp food) and swallowing (ingestion of food). Biting and swallowing responses were compared using magnetic resonance imaging of intact, behaving animals and a three-dimensional kinematic model. Biting is associated with larger amplitude protractions of the grasper (radula/odontophore) than swallowing, and smaller retractions. Larger biting protractions than in swallowing appear to be due to a more anterior position of the grasper as the behavior begins, a larger amplitude contraction of protractor muscle I2, and contraction of the posterior portion of the I1/I3/jaw complex. The posterior I1/I3/jaw complex may be context-dependent, i.e. its mechanical context changes the direction of the force it exerts. Thus, the posterior of I1/I3 may aid protraction near the peak of biting, whereas the entire I1/I3/jaw complex acts as a retractor during swallowing. In addition, larger amplitude closure of the grasper during swallowing allows an animal to exert more force as it ingests food. These results demonstrate that differential deployment of the periphery can mediate multifunctionality.
The desert ant odometer: a stride integrator that accounts for stride length and walking speed
Authors: Wittlinger Matthias , Wehner Rüdiger , Wolf Harald
Published: January 2007

Desert ants, Cataglyphis, use path integration as a major means of navigation. Path integration requires measurement of two parameters, namely,direction and distance of travel. Directional information is provided by a celestial compass, whereas distance measurement is accomplished by a stride integrator, or pedometer. Here we examine the recently demonstrated pedometer function in more detail.

By manipulating leg lengths in foraging desert ants we could also change their stride lengths. Ants with elongated legs ('stilts') or shortened legs('stumps') take larger or shorter strides, respectively, and misgauge travel distance. Travel distance is overestimated by experimental animals walking on stilts, and underestimated by animals walking on stumps - strongly indicative of stride integrator function in distance measurement.

High-speed video analysis was used to examine the actual changes in stride length, stride frequency and walking speed caused by the manipulations of leg length. Unexpectedly, quantitative characteristics of walking behaviour remained almost unaffected by imposed changes in leg length, demonstrating remarkable robustness of leg coordination and walking performance.

These data further allowed normalisation of homing distances displayed by manipulated animals with regard to scaling and speed effects. The predicted changes in homing distance are in quantitative agreement with the experimental data, further supporting the pedometer hypothesis.