bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue-Sensitive Afferents Inhibit Extensor but Not Flexor Motoneurons in Humans
Authors: Martin Peter G. , Smith Janette L. , Butler Jane E. , Gandevia Simon C. , Taylor Janet L.
Published: May 2006

The role of group III and IV muscle afferents in controlling the output from human muscles is poorly understood. We investigated the effects of these afferents from homonymous or antagonist muscles on motoneuron pools innervating extensor and flexor muscles of the elbow. In study 1, subjects (n= 8) performed brief maximal voluntary contractions (MVCs) of elbow extensors before and after a 2 min MVC of the extensors. During MVCs, electromyographic responses from triceps were evoked by stimulation of the corticospinal tracts [cervicomedullary motor evoked potentials (CMEPs)]. The same subjects repeated the protocol, but input from fatigue-sensitive afferents was prolonged after the fatiguing contraction by maintained muscle ischemia. In study 2, CMEPs were evoked in triceps during brief extensor MVCs before and after a 2 min sustained flexor MVC (n= 7) or in biceps during brief flexor MVCs before and after a sustained extensor MVC (n= 7). Again, ischemia was maintained after the sustained contractions. During sustained MVCs of the extensors, CMEPs in triceps decreased by ∼35%. Without muscle ischemia, CMEPs recovered within 15 s, but with maintained ischemia, they remained depressed (by ∼28%;p< 0.001). CMEPs in triceps were also depressed (by ∼20%;p< 0.001) after fatiguing flexor contractions, whereas CMEPs in biceps were facilitated (by ∼25%;p< 0.001) after fatiguing extensor contractions. During fatigue, inputs from group III and IV muscle afferents from homonymous or antagonist muscles depress extensor motoneurons but facilitate flexor motoneurons. The more pronounced inhibitory influence of these afferents on extensors suggests that these muscles may require greater cortical drive to generate force during fatigue.
Gene and protein expression in the myometrium in pregnancy and labor
Authors: Breuiller-Fouche Michelle , Germain Guy
Published: May 2006

Microarray technologies widen our comprehension of the major structural and metabolic transformations which affect the myometrium from the very beginning of pregnancy until parturition. The results are coherent with the mass of information which was accumulated previously, primarily on the basis of studies of selected critical factors. They highlight the activation of precise signaling pathways, some of which may have been previously under evaluated. The remodelling and maturation processes that the myometrium undergoes in pregnancy appear clearly as phenomena which last during the full course of gestation. Comparatively, the onset of labor is perhaps the phenomenon which remains the least well described by these methods of analysis. Nevertheless, genomic studies constitute a necessary first step of orientation and help establishing new links between the generic signaling pathways that are activated during the normal or pathological gestation. These studies also represent an indicative step that will have to be paralleled, in the future, with the results of the systematic proteomic analysis of the myometrium.
Uterotrophic effects of relaxin related to age and estrogen receptor activation in neonatal pigs
Authors: Yan Wenbo , Ryan Peter L , Bartol Frank F , Bagnell Carol A
Published: May 2006

While uterotrophic effects of relaxin are well documented, the mechanism through which relaxin promotes uterine growth is incompletely understood. Studies in rats suggest that relaxin-stimulated uterine edema depends on estrogen receptor (ER) activation. Here, neonatal pigs were used to investigate the interaction between relaxin and ER signaling pathways. Gilts were treated either at birth (postnatal day (PND) 0) (study 1) before the onset of endometrial ERα expression, or on PND 12 (study 2) after the onset of ERα expression. In study 1, gilts were treated with estradiol-17β or porcine relaxin for two days and uteri were collected on PND 2. In study 2, PND 12 gilts were treated with a single injection of the ER antagonist ICI 182,780 (ICI) or vehicle. Two hours later, gilts were given either estradiol-17β or porcine relaxin for two days. When administered for two days from birth (study 1), neither estradiol-17β nor relaxin affected uterine weight or protein content. However, uterine luminal epithelial height was greater in relaxin- than in vehicle-treated gilts. In contrast, in study 2, both estradiol and relaxin increased uterine weight, protein content and uterine luminal epithelial height on PND 14. These effects were inhibited by pre-treatment with ICI in both estradiol- and relaxin-treated gilts. The results indicate that uterotrophic effects of relaxin in the neonatal pig are related to age and to both the relative presence and state of activation of the ER system in developing uterine tissues between birth and PND 14.
Developmental regulation of prostacyclin synthase and prostacyclin receptors in the ovine uterus and conceptus during the peri-implantation period
Authors: Cammas L , Reinaud P , Bordas N , Dubois O , Germain G , Charpigny G
Published: May 2006

This study documents the expression of prostacyclin (PGI2) synthase (PTGIS) and PGI2 receptors in the trophoblast and uterus of the ewe at the time of maternal recognition of pregnancy (i.e. days 7, 9, 12, 14 and 17). The membrane receptor for PGI2 (PTGIR) and the nuclear receptors, i.e. peroxisome proliferator-activated receptors (PPAR) and their heterodimer partners the retinoid X receptors (RXR), were analysed. In the endometrium, PTGIS transcript and protein were expressed at day 9 of pregnancy and levels declined from days 12 to 17. Immunohistochemistry and in situ hybridization indicated that PTGIS was mainly located in the luminal epithelium of the endometrium. Endometrial PTGIR, PPARA, PPARG and RXRG expression was regulated during the peri-implantation period whereas PPARD, RXRA and RXRB were consistently expressed. In the trophoblast, PTGIS transcript levels rose as development progressed and peaked at day 17. PTGIR and PPARA transcripts peaked before day 12 and then declined and became nearly undetectable by day 17, whereas PPARD and PPARG transcript levels rose steadily from days 12 to 17. Because the PPARs and the RXRs display different expression profiles, we suggest that different heterodimers may form and support distinct functions as development proceeds. Our results also underline the importance of PTGIS and PPARD in the trophoblast and PTGIR in the uterus, suggesting that PGI2 is of both uterine and trophoblastic origin and is involved in a complex signalling pathway at around the time of implantation in the ewe.
Graft site and gonadotrophin stimulation influences the number and quality of oocytes from murine ovarian tissue grafts
Authors: Yang Hsiao Yun , Cox Shae-Lee , Jenkin Graham , Findlay Jock , Trounson Alan , Shaw Jillian
Published: May 2006

Ovarian tissue cryopreservation and subsequent transplantation can restore fertility in cancer patients. This study used a mouse ovarian grafting model to investigate whether the graft site (bursal cavity, the kidney capsule or subcutaneous) influences the number, fertilization rate and developmental potential of oocytes recovered from grafts and whether using a standard gonadotrophin stimulation protocol would increase oocyte yield from the grafts. Mouse ovarian tissue was grafted into four week old mice and collected three weeks later. Graft recipients were treated either with or without exogenous gonadotrophin stimulation prior to graft collection. Grafted ovaries yielded oocytes that were either at the germinal vesicle (GV) stage or mature metaphase II (MII) stage at collection. These GV oocytes were matured before in vitro fertilization (IVF), while the MII oocytes underwent IVF immediately. Oocytes collected from the oviducts of non-grafted superovulated mice of the same age served as controls. Two-cell embryos were transferred to pseudopregnant recipients and recovered at day 15 of gestation or left to go to term. Graft retrieval and the number of oocytes from each graft were lowest from the subcutaneous graft site. The number of two-cell embryos produced was significantly higher for oocytes from the grafts to the bursa as compared with the other sites. All graft sites gave rise to embryos with comparable implantation rates and developmental potential to fetuses and offspring following transfer. However, the oocytes from grafted ovaries had a significantly lower developmental potential when compared with the control group. Stimulation with exogenous gonadotrophins did not significantly increase oocyte yield from grafted ovaries but did enhance oocyte maturation and development. In conclusion, graft site affects the number and quality of oocytes produced from ovarian grafts.
Selective degradation of maternal and embryonic transcripts in in vitro produced bovine oocytes and embryos using sequence specific double-stranded RNA
Authors: Nganvongpanit Korakot , Müller Heike , Rings Franca , Hoelker Michael , Jennen Danyel , Tholen Ernst , Havlicek Vitezslav , Besenfelder Urban , Schellander Karl , Tesfaye Dawit
Published: May 2006

RNA interference (RNAi) has been used for selective degradation of an mRNA transcript or inhibiting its translation to a functional protein in various species. Here, we applied the RNAi approach to suppress the expression of the maternal transcript C-mos and embryonic transcripts Oct-4 in bovine oocytes and embryos respectively, using microinjection of sequence-specific double-stranded RNA (dsRNA). For this, 435 bp C-mos and 341 bp Oct-4 dsRNA were synthesized and microinjected into the cytoplasm of immature oocytes and zygotes respectively. In experiment 1, immature oocytes were categorized into three groups: those injected with C-mos dsRNA, RNase-free water and uninjected controls. In experiment 2, in vitro produced zygotes were categorized into three groups: those injected with Oct-4 dsRNA, RNase-free water and uninjected controls. The developmental phenotypes, the level of mRNA and protein expression were investigated after treatment in both experiments. Microinjection of C-mos dsRNA has resulted in 70% reduction of C-mos transcript after maturation compared to the water-injected and uninjected controls (P<0.01). Microinjection of zygotes with Oct-4 dsRNA has resulted in 72% reduction in transcript abundance at the blastocyst stage compared to the uninjected control zygotes (P<0.01). Moreover, a significant reduction in the number of inner cell mass (ICM) cells was observed in Oct-4 dsRNA-injected embryos compared to the other groups. From oocytes injected with C-mos dsRNA, 60% showed the extrusion of the first polar body compared to 50% in water-injected and 44% in uninjected controls. Moreover, only oocytes injected with C-mos dsRNA showed spontaneous activation. In conclusion, our results demonstrated that sequence-specific dsRNA can be used to knockdown maternal or embryonic transcripts in bovine embryogenesis.
Within and between breed differences in freezing tolerance and plasma membrane fatty acid composition of boar sperm
Authors: Waterhouse K E , Hofmo P O , Tverdal A , Miller R R
Published: May 2006

The response of sperm to cryopreservation and the fertility of frozen–thawed semen varies between species. Besides species differences in sperm physiology, structure and biochemistry, factors such as sperm transport and female reproductive tract anatomy will affect fertility of frozen–thawed semen. Therefore, studying differences in sperm cryotolerance between breeds and individuals instead of between species may reveal sources of variability in sperm cryotolerance. In the present study, the effect of cooling, re-warming and freezing and thawing on plasma membrane and acrosome integrity of sperm within and between Norwegian Landrace and Duroc breeds was studied. Furthermore, the relation between post-thaw survival rate and fatty acid composition of the sperm plasma membranes was investigated. Flow cytometry assessments of plasma membrane and acrosome integrity revealed no significant differences between breeds; however there were significant male-to-male variations within breeds in post-thaw percentages of live sperm (plasma membrane intact). The most abundant fatty acids in the plasma membranes from both breeds were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1, n-9), docosapentaenoic acid (22:5, n-6) and docosahexaenoic acid (22:6, n-3). The ratio of ∑ 22:5, n-6 and 22:6, n-3/∑ all other membrane fatty acids was significantly related to survival rate (plasma membrane integrity) of sperm for both Norwegian Landrace (correlation coefficient (rs) = 0.64, P < 0.05) and Duroc (rs = 0.67, P < 0.05) boars. In conclusion, male-to-male differences in sperm survival rate after freezing and thawing may be partly related to the amount of long-chain polyunsaturated fatty acids in the sperm plasma membranes.
Effectiveness of Population-Based Newborn Hearing Screening in England: Ages of Interventions and Profile of Cases
Authors: Uus Kai , Bamford John
Published: May 2006

OBJECTIVE. The objective of this study was to determine the effectiveness in routine practice of the first phase of a national population-based newborn hearing screening and follow-up program that seeks to identify infants with bilateral permanent hearing loss of ≥40-dB hearing loss.

METHODS. The study was a part of the independent evaluation of the 23 first phase sites (annual birth population ∼120000) of the national newborn hearing screening program in England. For each infant identified with the defined hearing loss, the measures of interest were degree and type of hearing loss, presence of risk factors, age of first audiologic assessment, age of identification of hearing loss, age of enrollment in an early support program, and age of hearing aid fitting. Data collection took place over the first 2 years of the program.

RESULTS. Data were provided on 169 infants with permanent bilateral moderate or greater hearing loss identified through screening 169487 infants. Fifty-four percent of all cases were from an “at-risk” population. Three fourths of these “at-risk” infants spent ≥48 hours in the NICU. For the whole sample, the median age at first audiologic assessment was 5 weeks; the median age of identification of the hearing loss and of enrollment in early support program was 10 weeks irrespective of the degree of hearing loss; and the median age at hearing aid fitting was 16 weeks. Infants with moderate hearing loss were fitted with hearing aids significantly later than those with severe and profound hearing loss.

CONCLUSIONS. Properly implemented, a newborn hearing screening program based on whole populations and routine service provision can deliver satisfactory outcomes in terms of age of referral, identification, and intervention. The distribution of degree and type of hearing loss and proportion with risk factors was similar to that expected. The numbers identified were such as to suggest that very few cases were missed by the screening program.
The Effect of Instituting a Prehospital-Discharge Newborn Bilirubin Screening Program in an 18-Hospital Health System
Authors: Eggert Larry D. , Wiedmeier Susan E. , Wilson Janie , Christensen Robert D.
Published: May 2006

OBJECTIVE. Kernicterus is a rare but devastating condition. The prevention of bilirubin-induced brain injury is based on the detection of infants at risk for developing severe hyperbilirubinemia. In an 18-hospital health system, Intermountain Health Care (IHC), we initiated a program of predischarge bilirubin screening of all neonates and coupled this with a results assessment using a percentile-based nomogram. Data during 2 periods of time, before versus after initiating the program, were compared to assess the effect of the program on significant hyperbilirubinemia and rehospitalization.

METHODS. We conducted a historic cohort study involving all neonates delivered at ≥35 weeks' gestation, within IHC's 18-hospital system, during 2 periods of time: March 1, 2001, to December 31, 2002, versus January 1, 2003, to December 31, 2004. A bilirubin screening program, instituted in December 2002, called for a total serum bilirubin (TSB) or transcutaneous bilirubin measurement to be performed on every neonate either at the recognition of clinical jaundice or before discharge regardless of whether jaundice was observed. For nonjaundiced neonates, the nursery staff was encouraged to obtain the screening TSB at the same time they obtained the state-mandated newborn screen for inborn errors of metabolism. Bilirubin values were plotted on an hour-specific nomogram and the corresponding percentile was used to guide evaluation, therapy, and follow-up. This study compared TSB data and readmission data for a 2-year period before versus a 2-year period after implementing the program.

RESULTS. The study involved 101272 neonates: 48789 in period 1 and 52483 in period 2. Before the program, 1 in every 77 neonates born at an IHC hospital had 1 or more serum bilirubin levels >20 mg/dL. After initiating the program, the incidence fell to 1 in 142 and the number of neonates with a level >25 mg/dL fell from 1 in 1522 before to 1 in 4037 after. The rate of hospital readmission with a primary diagnosis of jaundice fell from 0.55% in period 1 to 0.43% in period 2.

CONCLUSIONS. Initiating a program of bilirubin screening in a multihospital health system, coupled with evaluating the results using a percentile-based nomogram, reduced the proportion of neonates with significant hyperbilirubinemia and reduced the rate of hospital readmissions with jaundice.
Pain Assessment for Pediatric Patients in the Emergency Department
Authors: Drendel Amy L. , Brousseau David C. , Gorelick Marc H.
Published: May 2006

OBJECTIVE. To examine the relationship between pediatric patient visit characteristics and pain score documentation in the emergency department (ED) and determine whether documentation of a pain score is associated with increased analgesic use.

METHODS. A cross-sectional analysis was conducted of ED visits for pediatric patients from the National Hospital Ambulatory Medical Care Survey (1997–2000). Survey weighted regression first was used to assess the association between patient visit characteristics and pain score documentation. The regression then was repeated to determine the association between documentation of a pain score and analgesic use, adjusting for visit characteristics.

RESULTS. A total of 24707 visits were included. Only 44.5% of visits had documented pain scores. In the regression analysis, younger age, self-pay, visits to pediatric facilities, and visits that were not designated as injury related were associated with decreased pain score documentation. Documentation of pain score was associated with increased odds of an analgesic prescription and opioid prescription. When no pain score was documented, the odds of receiving any analgesic was similar to visits with pain documented as mild.

CONCLUSION. ED pain score documentation is suboptimal in the pediatric population. Infants and toddlers are at particular risk for not having a pain score documented. There is a significant association between pain score documentation and the use of any analgesic, particularly opioids. Improvements in pain documentation for acutely ill and injured children are needed to improve pain management.
All-chemical high-Jc YBa2Cu3O7 multilayers with SrTiO3 as cap layer
Authors: Pomar A. , Coll M. , Cavallaro A. , Gàzquez J. , González J.C. , Mestres N. , Sandiumenge F. , Puig T. , Obradors X.
Published: May 2006

We grew high-quality epitaxial YBa2Cu3O7 (YBCO) superconducting thin films by the trifluoroacetate route on top of chemical solution deposited SrTiO3 buffer layers. We show that high lattice mismatches can be accommodated in heterostructures grown by chemical methods. Clean interfaces were observed between the different layers. The influence of the buffer layer growth conditions on the final superconducting properties was studied in depth. We have proved that the main parameter affecting the YBCO critical currents is the SrTiO3 surface roughness, which promotes the nucleation of a/b axis grains and, as a consequence, the porosity of the YBCO film. On the other hand, an improved dependence of the critical current with perpendicular applied magnetic field was observed. This suggests a strengthened vortex pinning due to a higher density of a/b axis oriented grains.
Effects of temperature on interfacial reactions in γ–InSn4/Ni couples
Authors: Chen Sinn-wen , Lin Shih-kang
Published: May 2006

Interfacial reactions in γ–InSn4(Sn–20 at.% In)/Ni couples at 130, 140, 150, and 160 °C were investigated. Ni3Sn4phase with significant indium solubility was formed in the couple reacted at 130 and 140 °C, and the reaction path was γ–InSn4/Ni3Sn4/Ni. For the couples reacted at 150 and 160 °C, even though both γ–InSn4and Ni were solid phases, the liquid phase was formed in the couples. A distinguished feature was the nickel substrates becoming nonplanar with spikes at various locations and the Ni3Sn4phase layer on top of the nickel spikes. Except at regions near the nickel spikes, the reaction layer consisted of precipitates and was not a homogeneous phase. The reaction path is γ–InSn4/Ni3Sn4/Ni at the location with Ni3Sn4phase growing on Ni. However, if the Ni3Sn4phase does not nucleate, the liquid phase forms at the interface with accumulation of indium atoms, and the reaction path is γ–InSn4/ liquid/liquid + Ni3Sn4/Ni.
Synthesis of silicon carbide powders from fumed silica powder and phenolic resin
Authors: Ishihara Satoru , Tanaka Hidehiko , Nishimura Toshiyuki
Published: May 2006

Silicon carbide powders were synthesized by application of sol-gel processing. Fumed silica powder was used as the starting material for the silicon source, and phenolic resin was used for the carbon source. The effects of mixing ratio and difference between hydrophilic and hydrophobic types of fumed silica powders were investigated. The stirred mixtures of fumed silica powders and phenolic resin became apparent sol states owing to homogeneous distribution. SiC powders were formed derived from both the types of fumed silica powders after the gelation and pyrolysis up to 1800 °C. The hydrophilic silica powder was effective to synthesize more homogeneous SiC powders than the hydrophobic type. Single-phase SiC was obtained in the C/Si (molar ratio after pyrolysis at 1000 °C) range between 1.0 and 2.5, while free carbon was contained in the obtained powders of C/Si > 2.5. In contrast, formation of SiC was insufficient, and SiO2 was retained at ratios of C/Si < 1.0.
Synthesis and characteristics of curable siloxane-based organic-inorganic hybrid materials modified with vinyl and isopropenoxy
Authors: Kang Eun-Seok , Takahashi Masahide , Tokuda Yomei , Yoko Toshinobu
Published: May 2006

New curable organic-inorganic hybrid materials with a low internal optical attenuation of <0.35 dB/cm at the telecommunication wavelength and high thermal stability (∼370 °C) were synthesized by a nonhydrolytic reaction using vinyltriiospropenoxysilane (VTIPS) and diphenylsilanediol (DPSD) in which alcohol condensation takes place without hydrolysis of the starting materials. The molecular structure and the reaction mechanism of the synthesized organic-inorganic hybrid materials were investigated. The nonhydrolytic reaction of VTIPS and DPSD represented a high degree of condensation, and the molecules of the organic-inorganic hybrid materials exhibited the structure of an oligosiloxane modified with diphenyl, vinyl, and isopropenoxy. These organic-inorganic hybrid materials cured by polymerization of vinyl and isopropenoxy groups can be promising candidates for optical applications due to their good optical and thermal properties in addition to the availability of soft-lithography.
Morphology tuning in nontemplated solvothermal synthesis of titania nanoparticles
Authors: Wang Xin M. , Xiao Ping
Published: May 2006

Nanoparticles and nanocrystalline particles of pure anatase titania (TiO2) were synthesized by solvothermal processing of TiCl4 ethanol and isopropanol solutions at 120 to 200 °C. This one-step and nonsurfactant approach is versatile and the morphology tuning can be achieved by manipulating the growth kinetics. Dispersed nanocrystals of spherical, cubic, and acicular shapes and hollow spherical and core-shell structured micrometer-sized particles were obtained under different experimental conditions. The obtained hollow spherical- and core-shell–structured particles have an average diameter of 700 nm to 1.0 μm, with an average crystallite size of 5 to 16 nm. The dependence of nucleation/crystal growth and morphology development on solvothermal medium, reaction temperature, and reactant concentration was investigated. The reaction mechanism was then suggested and tentatively discussed from coordination and solution chemistry.
TaS2 nanoplatelets produced by laser ablation
Authors: Chick Ka Yee , Nath Manashi , Parkinson B.A.
Published: May 2006

Tantalum disulfide (TaS2) nanoplatelets were produced by laser ablation of a TaS2 target under an argon atmosphere. The nanoplatelet dimensions and morphology were characterized by transmission electron microscopy and x-ray diffraction. The effect of the ablation laser power density on the size distribution of the nanoplatelets was studied. The TaS2 nanoplatelets were prone to oxidation upon exposure to air but could be stabilized by using 3-mercaptopropionic acid as the capping agent.
Formation of convex shaped poly(phenylsilsesquioxane) micropatterns on indium tin oxide substrates with hydrophobic-hydrophilic patterns using the electrophoretic sol-gel deposition method
Authors: Takahashi Kenji , Tadanaga Kiyoharu , Matsuda Atsunori , Hayashi Akitoshi , Tatsumisago Masahiro
Published: May 2006

Hydrophobic-hydrophilic patterns were formed on indium tin oxide substrates, and thick films of poly(phenylsilsesquioxane) (PhSiO3/2) particles, prepared by the sol-gel process, were selectively deposited onto hydrophilic areas of the substrates by electrophoresis. The films composed of PhSiO3/2 particles became transparent with morphological changes from aggregates of particles to a continuous phase after a heat treatment. After heat treatment at 200 °C, convex-shaped PhSiO3/2 micropatterns were formed on the hydrophilic region of the pattern. Moreover, the height of micropatterns was controlled by the deposition time. This patterning technique has a wide variety of applications such as fabrication of micro-optical components.
Sol-gel synthesis of a nanoparticulate aluminosilicate precursor for homogeneous mullite ceramics
Authors: Leivo Jarkko , Lindén Mika , Teixeira Cilâine V. , Puputti Janne , Rosenholm Jessica , Levänen Erkki , Mäntylä Tapio A.
Published: May 2006

An amorphous nanoparticulate aluminosilicate 3/2-mullite precursor has been synthesized and carefully characterized. The sol contained 2-nm particles of Q3(3Al) silica species together with six-coordinated alumina, which suggested an allophane-like structure of the nanoparticles. The sol remained stable for years, and formed an easily redispersible physical gel upon solvent evaporation. The gel crystallized to mullite at temperatures below 1000 °C, without going through any intermediate spinel phase. Thus, the nanoparticulate precursor is regarded as a homogeneous high-purity mullite precursor with a high Si–O–Al bond density, which is useful in the preparation of various nanostructured Al-rich aluminosilicate materials. The sols and gels were characterized by small-angle x-ray scattering, dynamic light scattering, x-ray diffraction, 27Al and 29Si magic-angle spinning (MAS) nuclear magnetic resonance spectroscopy, and differential thermal analysis.
New expanding cavity model for indentation hardness including strain-hardening and indentation size effects
Authors: Gao X.-L.
Published: May 2006

An expanding cavity model (ECM) for determining indentation hardness of elastic–strain-hardening plastic materials is developed. The derivation is based on a strain gradient plasticity solution for an internally pressurized thick-walled spherical shell of an elastic linear-hardening material. Closed-form formulas are provided for both conical and spherical indentations. The formulas explicitly show that indentation hardness depends on Young's modulus, yield stress, strain-hardening index, and strain gradient coefficient of the indented material as well as on the geometry of the indenter. The newly formulated ECM can capture the indentation size effect, unlike classical plasticity based ECMs. The new model reduces to existing classical plasticity based ECMs (including Johnson's ECM for elastic-perfectly plastic materials) when the strain gradient effect is not considered. The presently developed ECM is validated by comparing with existing experimental hardness data. The numerical results obtained using the new model reveal that the hardness is indeed indentation size dependent when the indentation radius is very small: the smaller the indentation, the larger the hardness. Also, the indentation hardness is seen to increase with the Young's modulus and strain-hardening level of the indented material for both conical and spherical indentations. The strain-hardening effect on the hardness is observed to be significant for materials having strong strain-hardening characteristics. In addition, it is found that the indentation hardness increases with decreasing cone angle of the conical indenter or decreasing radius of the spherical indenter. These trends agree with existing experimental observations and model predictions.
Growth and structure of heteroepitaxial lead titanate thin films constrained by miscut strontium titanate substrates
Authors: Ichikawa Yoko , Matsunaga Toshiyuki , Hassan Mohsen , Kanno Isaku , Suzuki Takaaki , Wasa Kiyotaka
Published: May 2006

Single-crystal lead titanate [(001)PbTiO3 (PT)] thin films were heteroepitaxially grown on a miscut strontium titanate [(001)SrTiO3 (ST)] substrate by radio frequency magnetron sputtering. The PT thin films were grown via a step-flow growth. The step-flow growth enhanced the layer growth resulting in the continuous (001) single-crystal structure without a dislocated interface for the film thickness below 200 to 250 nm. The PT thin films show a small temperature variation of the lattice parameters unlikely to the bulk PT crystals due to the substrate clamping. The temperature variation of the lattice constants is discussed in terms of the thermo-elastic deformation analysis for the PT/ST heterostructure.
The Graying of America: Implications for Health Professionals
Authors: Wright James D.
Published: May 2006

Demographic projections confirm a dramatic increase in the size of America’s elderly population over the next several decades. The elderly now comprise 13% of the population; by 2045, they will comprise 22%. As the elderly population grows, so too will the elderly poor, the elderly homeless, and the elderly uninsured. The implications of the so-called graying of America for the health care system, particularly the long-term care industry, are staggering.
“We Have Our Protector”: Misperceptions of Protection Against HIV Among Participants in a Microbicide Efficacy Trial
Authors: Mantell Joanne E. , Morar Neetha S. , Myer Landon , Ramjee Gita
Published: May 2006

Objectives. We examined perceptions of the effectiveness and acceptability of a candidate microbicide among 94 South African female sex workers who had participated in a phase 3 microbicide trial for HIV prevention.

Methods. Sixteen focus groups were conducted in 2001, 12 to 15 months after participants were informed that the candidate microbicide had been determined to be ineffective in preventing HIV and other sexually transmitted infections (STIs).

Results. Participants clearly indicated that they understood the experimental nature of the candidate microbicide, and they recognized that they had been informed after the trial that the product was ineffective. Nevertheless, most continued to believe that the candidate microbicide helped prevent HIV and other STIs, alleviated reproductive tract pain and STI symptoms, and helped to clean the vagina.

Conclusions. These findings underscore the importance of understanding women’s perceptions of the efficacy of candidate microbicides and the rationale for these beliefs. These issues need to be addressed in counseling throughout microbicide trials for HIV prevention. These results also demonstrate how desperate many women at high risk of HIV infection may be for new HIV prevention technologies.
Prevalence of HIV Infection Among Young Adults in the United States: Results From the Add Health Study
Authors: Morris Martina , Handcock Mark S. , Miller William C. , Ford Carol A. , Schmitz John L. , Hobbs Marcia M. , Cohen Myron S. , Harris Kathleen M. , Udry J. Richard
Published: May 2006

Objectives. We estimated HIV prevalence rates among young adults in the United States.

Methods. We used survey data from the third wave of the National Longitudinal Study of Adolescent Health, a random sample of nearly 19000 young adults initiated in 1994–1995. Consenting respondents were screened for the presence of antibodies to HIV-1 in oral mucosal transudate specimens. We calculated prevalence rates, accounting for survey design, response rates, and test performance.

Results. Among the 13184 participants, the HIV prevalence rate was 1.0 per 1000 (95% confidence interval [CI] = 0.4, 1.7). Gender-specific prevalence rates were similar, but rates differed markedly between non-Hispanic Blacks (4.9 per 1000; 95% CI=1.8, 8.7) and members of other racial/ethnic groups (0.22 per 1000; 95% CI=0.00, 0.64).

Conclusions. Racial disparities in HIV in the United States are established early in the life span, and our data suggest that 15% to 30% of all cases of HIV occur among individuals younger than 25 years.
Health Care Access Among Individuals Involved in Same-Sex Relationships
Authors: Heck Julia E. , Sell Randall L. , Gorin Sherri Sheinfeld
Published: May 2006

Objectives. We used data from the National Health Interview Survey to compare health care access among individuals involved in same-sex versus opposite-sex relationships.

Methods. We conducted descriptive and logistic regression analyses from pooled data on 614 individuals in same-sex relationships and 93418 individuals in opposite-sex relationships.

Results. Women in same-sex relationships (adjusted odds ratio [OR]=0.60; 95% confidence interval [CI]=0.39, 0.92) were significantly less likely than women in opposite-sex relationships to have health insurance coverage, to have seen a medical provider in the previous 12 months (OR=0.66; 95% CI=0.46, 0.95), and to have a usual source of health care (OR=0.50; 95% CI=0.35, 0.71); they were more likely to have unmet medical needs as a result of cost issues (OR=1.85; 95% CI=1.16, 2.96). In contrast, health care access among men in same-sex relationships was equivalent to or greater than that among men in opposite-sex relationships.

Conclusions. In this study involving a nationwide probability sample, we found some important differences in access to health care between individuals in same-sex and opposite-sex relationships, particularly women.
Recruiting Minority Men Who Have Sex With Men for HIV Research: Results From a 4-City Campaign
Authors: Silvestre Anthony J. , Hylton John B. , Johnson Lisette M. , Houston Carmoncelia , Witt Mallory , Jacobson Lisa , Ostrow David
Published: May 2006

We describe the efforts of a 4-city campaign to recruit Black and Hispanic men who have sex with men into an established HIV epidemiological study. The campaign used community organizing principles and a social marketing model that focused on personnel, location, product, costs and benefits, and promotion. The campaign was developed at the community, group, and individual levels to both increase trust and reduce barriers.

The proportion of Hispanic men recruited during the 2002–2003 campaign doubled compared with the 1987 campaign, and the proportion and number of White men decreased by 20%. The proportion of Black men decreased because of the large increase in Hispanic men, although the number of Black men increased by 56%.

Successful recruitment included training recruitment specialists, involving knowledgeable minority community members during planning, and having an accessible site with convenient hours.
Conifer Seed Survival in a Western Oregon Clearcut
Authors: Gashwiler Jay S.
Published: May 2006

A study of the survival of naturally disseminated tree seed was made in a clearcut area on the H. J. Andrews Experimental Forest in the Cascade Range of western Oregon during 1955–60. From start of seed fall until the end of germination in late spring following year, 12% of the Douglas‐fir (Pseudotsuga menziesii) seed survived. Ground‐feeding birds and small mammals caused 63% of the seed loss and other agents 25%. Thirty‐one per cent of the seed of western hemlock (Tsuga heterophylla) lived from the start of seed fall until the end of germination. Of the amount lost, birds and mammals took 16% and all other factors 53%. A large proportion (65%) of western redcedar (Thuja plicata) seed survived during the same period. The entire loss was attributed to causes such as nonviable filled seeds, disease, invertebrates, and others. Ground‐feeding birds and small mammals showed a definite preference for Douglas‐fir seeds. Only about 25% as many hemlock seeds were taken, and redcedar was not consumed in appreciable amounts. Most of the seed depredations by birds and mammals occurred from start of seed fall to start of germination; other factors took heaviest toll during the germination period.
Ecology of Zooplankton, Benthos and Fishes in the Columbia River Estuary
Authors: Haertel Lois , Osterberg Charles
Published: May 2006

Fauna of the Columbia River estuary were sampled regularly for 21 months. Analyses of plankton samples indicated that three distinct populations existed in the estuary: a freshwater group, a marine group, and an indigenous estaurine group. The latter consisted principally of a large population of Eurytemora hirundoides. Changes in the salinity of the estuary were reflected in the composition of the plankton. The majority of the fish and benthic invertebrates found in the estuary are euryhaline. The largest numbers of fish species, as well as the largest numbers of individuals, occupy the slightly brackish waters of the central portion of the estuary. the major plankton blooms also occur in this area. Starry flounder (Platichthys stellatus) and sand shrimp (Crangon franciscorum) use the upper estuary as a nursery ground. Extensive analyses of fish stomach contents confirm that food habits of fishes generally reflect the availability of prey.
Caloric Values of Organic Matter in Woodland, Swamp, and Lake Soils
Authors: Gorham Eville , Sanger Jon
Published: May 2006

Caloric values were determined on an ash—free dry—weight basis for organic matter in woodland, swamp, and lake soils and in certain plants. Mean values in kilocalories per gram are: 11 woodland soils, 5.04; 20 swamp soils, 4.87; 9 lake sediments, 5.24; 10 tree—leaf samples, 5.22; 9 samples of aboveground parts of the ground flora, 4.65; 4 aquatic algae, 5.23; and 4 aquatic macrophytes, 4.31.
Effect of Shade on Leaf Structure of Deciduous Tree Species
Authors: Jackson L. W. R.
Published: May 2006

Sun and shade leaves of 21 deciduous tree species were measured and tissue development compared. Species considered tolerant of shade had normally thinner sun leaves and less reduction in thickness in shade than did species considered intolerant. Sun—leaf/shade leaf ratios in the palisade layer were 1.22, 1.32, and 2.36 for the tolerant, intermediate, and intolerant classes respectively, while for the mesophyll the equivalent ratios were 1.9, 1.27, and 1.51. Thickness of both palisade and spongy tissue was highly correlated with blade thickness in both sun— and shade—grown leaves. Druse and prismatic crystals were prevalent in the mesophyll and vascular tissues of 14 species.
Ecological Response of Sagebrush‐Grass Range in Central Oregon to Mechanical and Chemical Removal of Artemisia
Authors: Hedrick D. W. , Hyder D. N. , Sneva F. A. , Poulton C. E.
Published: May 2006

Big sagebrush was controlled by rotobeating and spraying on both fair— and poor—condition ranges. A randomized block design was used with two replications of each treatment (untreated, sprayed, and rotobeaten). Data were taken from 10 permanent sampling units within each treatment plot. Numbers and crown cover of big sagebrush on treated range in fair condition changed little in 8 years after treatment. However, on poor—condition ranges sagebrush rapidly reoccupied mechanically treated areas. Some sagebrush increase occurred on sprayed poor—condition ranges, but brush numbers are strikingly lower than on rotobeaten plots. Herbage yields corrected to median—year precipitation varied considerably on untreated and treated plots, but herbage production was at least doubled, mostly from increaser—type species, on both sprayed and mechanically treated fair—condition range. On poor—condition ranges, herbage response was primarily from annuals with a marked trend toward an increasing amount of cheatgrass on treated plots. Soil moisture contents are generally greater on treated plots until the deep—rooted herbage species increase considerably. Soil temperatures are consistently lower on poor—condition, rotobeaten plots, and this difference is attributed to the insulating effect of the persistent woody residue on the soil surface.
Use of Glucose and Acetate by Bacteria and Algae in Aquatic Ecosystems
Authors: Wright Richard R. , Hobbie John E.
Published: May 2006

New methods employing C14—Labeled organic compounds measure the uptake of organic solutes by planktonic microorganisms. By testing uptake over a wide range of substrate concentrations, two separate mechanisms can be differentiated and their kinetics measured. Using filtration and evidence from experiments with laboratory cultures of planktonic bacteria and algae, specific transport systems effective at very low substrate concentrations were traced to the bacteria, and a diffusion mechanism, effective only at higher substrate concentrations, to the algae. Studies have shown that V, the maximum velocity of uptake by bacterial transport systems, gives information about the size and function of the bacterial populations. A diffusion constant, kd, gives information on the rate of uptake of solutes by the algal populations. Turnover times, derived from kinetic parameters, indicate that the algal uptake of glucose and acetate in Lake Erken, Sweden, is always less than 10% of the bacterial uptake, even though the algal biomass may be orders of magnitude greater than the bacterial. Two new types of bioassay employ the kinetics of bacterial uptake systems as the measuring reaction. Acetate and glucose were found in 1—10 mg/liter concentrations in the several natural waters tested. At these very low concentrations, algal uptake of glucose and acetate is so low that effective heterotrophy is impossible. In contrast, the bacteria effectively remove substrate from solution at these low levels and probably keep the substrate at these low concentrations. By doing this, the bacteria may prevent heterotrophic growth of algae in nature.
Population Ecology of Feral House Mice: Interference by Microtus
Authors: Delong Karl T.
Published: May 2006

House mouse populations were studied from October 1963 until May 1964 in the presence and absence of meadow mice by experimentally manipulating two field grids. Supplemental food was supplied to the grids to eliminate food as a variable in the interaction between the two species. The rate of population increase for Mus was halved in the presence of Micortus in spite of nearly equal body growth rates, reproductive rates, and survival rates of trappable house mice on the two areas. However, recruitment of young into the trappable population was halved in the presence of Microtus. These field data and the data from a laboratory study of the two species in artificial burrow systems indicated that Microtus caused mortality of Mus nestlings.
Photosynthetic Efficiency at Reduced Carbon Dioxide Tensions
Authors: Mooney H. A. , Strain B. R. , West Marda
Published: May 2006

Plants of Erigeron clokeyi, Haplopappus apargioides, Chamaebatiaria millefolium, and Encelia californica were grown at elevations of 1,250 and 3,094 m for at least 4 weeks in the White Mountains of California. During this period the photosynthetic temperature response was different at the two elevations. However, there was no apparent photosynthetic acclimation to differences in the CO2 tensions of the two growth environments.
Vegetation Types in the Las Bela Region of West Pakistan
Authors: Snead Rodman E. , Tasnif Mohammad
Published: May 2006

Six main types of soil and terrain were recognized on the Las Bela coastal plain of West Pakistan. Usually one or two species of plants–indicator species–predominated on each of the terrain types. Other plants grew in close association with the indicator species but could not be classified as indicators because their locale was not restricted to a specific landform. The identification of indicator species on aerial photographs helped to determine boundaries for the landforms.
The Role of Pelagic Crags in the Grazing of Phytoplankton Off Baja California
Authors: Longhurst Alan R. , Lorenzen Carl J. , Thomas William H.
Published: May 2006

The galathied crab Pleuronocodes planipes, which occurs in very dense and extensive pelagic concentrations to the west of Baja California, is capable of filter—feeding on natural diatom blooms. Its filtering mechanism is similar to that previously known in Porcellana. It is only in regions of coastal diatom blooms that Pleuroncodes feeds exclusively on Phytoplankton; elsewhere, it feeds on protista and zooplankters. A study of production and grazing in a coastal upwelling situation suggested that the observed zooplankton community would have incapable of sustaining more than about 10% of the apparent grazing rate, and calculations based on estimated grazing rates for Pleuroncodes suggested that the observed standing stock of this species could go far towards supplying the remainder of the apparent grazing pressure. Pelagic crabs may thus, at least in certain situations, play a dominant role in grazing down diatom blooms in the southern part of the California Current.
Zonation of Nearshore Mysids
Authors: Clutter Robert I.
Published: May 2006

Between the shore and 17 m depth, over sand bottom on the open coast of southern California, five species of hypopelagic mysids and four species of benthic mysids occurred in bathymetric zones roughly parallel with the shore. The possible causes and function of zonation of the numerically dominant pelagic species were examined. The information suggests that the zonation may have developed as observed mainly in response to the pattern of availability of food that was imposed by the nearshore circulation system, and that competitive exclusion of other pelagic specied occurred. The zonation may provide a situation wherein population control can be effected by changes in reproduction rate.
Primary Conifer Succession, Lassen Volcanic National Park
Authors: Heath James P.
Published: May 2006

Mudflows and avalanches extending over at least 1,500 years presented a nearly ideal successional series. Nine species of conifer were present on these dacitic substrates. Spread of disseminules is apparently very important in determining composition in the first several hundred years. Conifers are capable of successful invasion of raw substrates, and the earliest conifer population is essentially determined by physical factors. More permanent and fully recorded study plots are needed in protected reserves.
A Mathematical Model for Tribolium Confusum Populations N. W. Taylor
Authors: Taylor N. W.
Published: May 2006

A deterministic mathematical model is constructed to describe the population growth in colonies of the grain beetle, Tribolium confusum, under laboratory conditions. It is shown how (1) changes in the egg laying rate and the adult mortality, (2) the destruction of some eggs by larvae as well as by adults, and (3) the destruction of some small larvae by larvae and adults, lead to a theoretical population growth which agrees closely with the laboratory experiments.