bluuebunny/crossref_metadata_2025 huggingface dataset:
91 A NOVEL TECHNIQUE FOR EVALUATION OF THE LIPID CONTENT IN PIG EMBRYOS
Authors: Romek M. , Gajda B. , Krzysztofowicz E. , Smorag Z.
Published: January 2008

A high level of lipids, mainly triglycerides and fatty acids, present in embryo cells in the form of lipid droplets is the major factor associated with low cryopreservation of porcine embryos. Previous results demonstrated that the low tolerance of pig embryos to cryopreservation can be increased through reduction of lipid droplet contents. Therefore, in order to improve cryopreservation techniques of porcine embryos, it is fundamental to establish proper culture conditions which ultimately will enable a decrease in lipid content. Unfortunately, there are no precise and efficient methods to evaluate the lipid contents of single pig embryos. Previously used stereological analysis combined with physical serial sectioning (Romek et al. 2007 Reprod. Domest. Anim. in press) is time-consuming, and measurement of triglyceride levels based on enzymatic hydrolysis eliminates other types of lipids from the analysis. Taking the above problems into account, we have developed a new method for evaluation of total lipid content in pig embryos. It is based on visualization of lipid droplets using the specific fluorescent dye Nile red and applying confocal scanning microscopy followed by the Cavalieri method. This method enables measurement of several stereological parameters, especially the volume density of lipid droplets per unit volume of cytoplasm Vv(fat,c), which quantifies most precisely the amount of intracellular lipid. The experiment was carried out on 2- to 4-cell and 8- to 16-cell pig embryos, morulae, blastocysts, and late blastocysts cultured in vitro. Embryos were developed from in vivo-produced zygotes to appropriate stages of development in North Carolina State University (NCSU) 23 medium. For each stage, ten of the embryos were examined. Embryos were denuded and fixed with 2% glutaraldehyde and 2% formaldehyde, stained with 100 nm Nile red (Molecular Probes, Leiden, The Netherlands), and analyzed by means of a confocal microscope LSM 510 Meta (Carl Zeiss MicroImaging GmbH, G�ttingen, Germany). Serial optical sections of each individual embryo were measured by the point counting method, and then the Cavalieri method was used to estimate Vv(fat,). Vv(fat,c) values calculated for embryos at different stages of development were compared by one-way analysis of variance and Tukey's intervals. For cultured pig embryos, volume density of lipid droplets Vv(fat,c) significantly decreased during cleavage from 0.55 µm3 µm–3 at the 2- to 4-cell-embryo stage to 0.46 µm3 µm–3 at the blastocyst stage. The differences between lipid droplet volumes calculated for morulae, blastocysts, and late blastocysts were statistically significant. In conclusion, our new method is more precise, efficient, and quick in comparison to previously used ones. Moreover, we confirmed that the content of total lipids in cultured pig embryo is reduced during its development.
This research was funded by the State Committee for Scientific Research (Project No. 2 P06D 003 26) and Net of Reproduction Biotechnology.
The oldest platypus and its bearing on divergence timing of the platypus and echidna clades
Authors: Rowe Timothy , Rich Thomas H. , Vickers-Rich Patricia , Springer Mark , Woodburne Michael O.
Published: January 2008

Monotremes have left a poor fossil record, and paleontology has been virtually mute during two decades of discussion about molecular clock estimates of the timing of divergence between the platypus and echidna clades. We describe evidence from high-resolution x-ray computed tomography indicating thatTeinolophos, an Early Cretaceous fossil from Australia's Flat Rocks locality (121–112.5 Ma), lies within the crown clade Monotremata, as a basal platypus. Strict molecular clock estimates of the divergence between platypus and echidnas range from 17 to 80 Ma, butTeinolophossuggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their divergence may predate even the oldest strict molecular estimates by at least 50%. We generated relaxed molecular clock models using three different data sets, but only one yielded a date overlapping with the age ofTeinolophos. Morphology suggests thatTeinolophosis a platypus in both phylogenetic and ecological aspects, and tends to contradict the popular view of rapid Cenozoic monotreme diversification. Whereas the monotreme fossil record is still sparse and open to interpretation, the new data are consistent with much slower ecological, morphological, and taxonomic diversification rates for monotremes than in their sister taxon, the therian mammals. This alternative view of a deep geological history for monotremes suggests that rate heterogeneities may have affected mammalian evolution in such a way as to defeat strict molecular clock models and to challenge even relaxed molecular clock models when applied to mammalian history at a deep temporal scale.
Adaptation increases the likelihood of diversification in an experimental bacterial lineage
Authors: Spencer Christine C. , Tyerman Jabus , Bertrand Melanie , Doebeli Michael
Published: January 2008

Understanding the mechanisms and processes that generate biological diversity is a fundamental problem in evolution and ecology. In the past decade, the theory of evolutionary branching and adaptive diversification has provided new perspectives for understanding the evolution of diversity caused by ecological interactions. In models of adaptive diversification, the fitness landscapes change dynamically, so that the likelihood of diversification into different phenotypic clusters increases over time. In contrast, in models with static fitness landscapes, the likelihood of diversification decreases as populations climb fitness peaks, because crossing maladaptive fitness valleys becomes increasingly difficult. We used experimental evolution in bacteria to test how the likelihood of diversification changes over time in a bacterial lineage that has diversified in sympatry from a single ancestral strain. By analyzing the “fossil” record of this lineage, and restarting the lineage from different time points in the evolutionary past, we demonstrate that: (
i
) the lineage has initially undergone a phase of directional adaptation to the competitive environment, and (
ii
) during this phase, the likelihood of diversification increases significantly over time. These results suggest evolutionary branching caused by frequency-dependent competition as the main mechanism of diversification in our experimental populations.
Selective aluminum passivation for targeted immobilization of single DNA polymerase molecules in zero-mode waveguide nanostructures
Authors: Korlach Jonas , Marks Patrick J. , Cicero Ronald L. , Gray Jeremy J. , Murphy Devon L. , Roitman Daniel B. , Pham Thang T. , Otto Geoff A. , Foquet Mathieu , Turner Stephen W.
Published: January 2008

Optical nanostructures have enabled the creation of subdiffraction detection volumes for single-molecule fluorescence microscopy. Their applicability is extended by the ability to place molecules in the confined observation volume without interfering with their biological function. Here, we demonstrate that processive DNA synthesis thousands of bases in length was carried out by individual DNA polymerase molecules immobilized in the observation volumes of zero-mode waveguides (ZMWs) in high-density arrays. Selective immobilization of polymerase to the fused silica floor of the ZMW was achieved by passivation of the metal cladding surface using polyphosphonate chemistry, producing enzyme density contrasts of glass over aluminum in excess of 400:1. Yields of single-molecule occupancies of ≈30% were obtained for a range of ZMW diameters (70–100 nm). Results presented here support the application of immobilized single DNA polymerases in ZMW arrays for long-read-length DNA sequencing.
Preferential protection of protein interaction network hubs in yeast: Evolved functionality of genetic redundancy
Authors: Kafri Ran , Dahan Orna , Levy Jonathan , Pilpel Yitzhak
Published: January 2008

The widely observed dispensability of duplicate genes is typically interpreted to suggest that a proportion of the duplicate pairs are at least partially redundant in their functions, thus allowing for compensatory affects. However, because redundancy is expected to be evolutionarily short lived, there is currently debate on both the proportion of redundant duplicates and their functional importance. Here, we examined these compensatory interactions by relying on a genome wide data analysis, followed by experiments and literature mining in yeast. Our data, thus, strongly suggest that compensated duplicates are not randomly distributed within the protein interaction network but are rather strategically allocated to the most highly connected proteins. This design is appealing because it suggests that many of the potentially vulnerable nodes that would otherwise be highly sensitive to mutations are often protected by redundancy. Furthermore, divergence analyses show that this association between redundancy and protein connectivity becomes even more significant among the ancient duplicates, suggesting that these functional overlaps have undergone purifying selection. Our results suggest an intriguing conclusion—although redundancy is typically transient on evolutionary time scales, it tends to be preserved among some of the central proteins in the cellular interaction network.
Cocaine Withdrawal Symptoms Identify “Type B” Cocaine‐Dependent Patients
Authors: Ahmadi Jamshid , Kampman Kyle , Dackis Charles , Sparkman Thorne , Pettinati Helen
Published: January 2008

Recent studies of substance dependence typologies briefly show that multivariate systems originally developed for identifying subtypes of alcoholics, such as Babor's Type A and B system, may also be valid in abusers of other substances, such as cocaine. Type B patients are characterized by an earlier onset of addiction and more severe symptoms of their addiction, psychopathology, and impulsivity. The Type B classification has also been associated with deficits in serotonergic function. We have found that patients who exhibit more severe cocaine withdrawal symptoms, as measured by scores on the Cocaine Selective Severity Assessment (CSSA), have poor treatment outcome and share many characteristics with “Type B” patients. In this paper, we review baseline characteristics of cocaine‐dependent patients from several recently completed outpatient cocaine dependence treatment trials to assess the association of cocaine withdrawal symptom severity and the Type B profile. Identifying subtypes of cocaine‐dependent patients may improve our ability to treat cocaine dependence by targeting treatments for specific subtypes of patients. We examined the ability of the CSSA scores to capture Type B characteristics in cocaine dependence by analyzing a series of cocaine medication trials that included 255 cocaine‐dependent subjects. High CSSA scores at baseline were associated with a history of violent behavior, a family history of substance abuse, antisocial personality disorder, higher addiction severity, and co‐morbid psychiatric diseases. Patients with high CSSA scores are also more likely to meet criteria for Type B (Type II) cocaine dependence. Identifying Type B cocaine‐dependent patients may help to develop targeted psychosocial or pharmacological treatments for these difficult‐to‐treat patients.
Neurobiological Processes in Adolescent Addictive Disorders
Authors: Schepis Ty S. , Adinoff Bryon , Rao Uma
Published: January 2008

The purpose of this review is to summarize the neurobiological factors involved in the etiology of adolescent addiction and present evidence implicating various mechanisms in its development. Adolescents are at heightened risk for experimentation with substances, and early experimentation is associated with higher rates of SUD in adulthood. Both normative (e.g., immature frontal‐limbic connections, immature frontal lobe development) and non‐normative (e.g., lowered serotonergic function, abnormal hypothalamic‐pituitary‐adrenal axis function) neurobiological developmental factors can predispose adolescents to a heightened risk for SUD. In addition, a normative imbalance in the adolescent neurobiological motivational system may be caused by the relative underdevelopment of suppressive mechanisms when compared to stimulatory systems. These neurobiological liabilities may correspond to neurobehavioral impairments in decision‐making, affiliation with deviant peers and externalizing behavior; these and other cognitive and behavioral traits converge with neurobiological factors to increase SUD risk. The progression to SUD acts as an amplifying feedback loop, where the development of SUD results in reciprocal impairments in neurobehavioral and neurobiological processes. A clearer understanding of adolescent neurobiology is a necessary step in the development of prevention and treatment interventions for adolescent SUD.
Methamphetamine‐Using Felons: Psychosocial and Behavioral Characteristics
Authors: Semple Shirley J. , Zians Jim , Strathdee Steffanie A. , Patterson Thomas L.
Published: January 2008

Methamphetamine (meth) users with felony convictions may be important vectors in the HIV/AIDS pandemic because of their drug and sexual risk histories. This study gathered personal, psychosocial, and behavioral data from 450 HIV‐negative, heterosexually identified, meth‐using men and women. Significant differences were found between felons and non‐felons in meth use patterns, contexts and reasons for use, involvement of social networks in meth use, and certain psychosocial and sexual risk variables. Our findings suggest that targeting meth use patterns and motivations, social networks, and sexual risk behaviors of meth‐using felons may help to reduce HIV/AIDS transmission in and outside the prison system.
The interaction of methodology with an impegno del dopo in Nuto Revelli's collections of oral testimonies
Authors: Stewart Fiona M.
Published: January 2008

Among his varied publications, Nuto Revelli (1919–2004) produced three collections of oral testimonies gathered from the contadini (peasants) of Piedmont: La strada del davai, Il mondo dei vinti and L’anello forte. This article argues that these collections were the product of the same specific impegno del dopo (‘obligation of afterwards’) as his initial autobiographical writings, which had arisen from his experiences as an officer on the Russian Front during the Second World War. From this premise, the article then examines the interaction of Revelli's sense of impegno del dopo with the methodology he developed. The article concludes with an assessment of Revelli's stated aims and his actual achievements.
Structures and Properties of Cast Irons Reinforced by Trace Addition of Modified SiC Nanopowders
Authors: Li Jian-wei , Chen Mei-ling , Gao Hong , Zhao Ying-hua
Published: January 2008

To improve the performance of traditional cast iron, trance amount of surface modified nanometer SiC powders were added into the melted iron. The microstructures, the mechanical properties, as well as the wear resistance were investigated. The trace addition of SiC nano-powders were active due to the presence of structural defects arising from the treatment, they were efficient in affecting not only the generation and growth of crystals but also change the morphology of graphite. On the other hand, the addition of SiC nano-powders as heterogeneous seedings in the crystallization of liquid metals lead to the changing of supercooling temperature, so the ratio of ferrite and pearlite was changed. The mechanical characteristics and wear resistance were enhanced as a result of the improved graphite shape and changed matrix composition caused by the trace addition of SiC nanopowders (in amounts of about 0.01% mass). The strengthening mechanism and the free gap between powders were also discussed. It is suggested that the tensile strength, toughness, as well as the wear resistance can be improved simultaneously, which indicates the novel strengthening technology by trace addition of nanopowders is promising to extend to large-scale industrial production.
Influential Factors of Low-energy C36 Cluster Deposition on Diamond (100) Crystal Plane
Authors: Chen Ming-jun , Liang Ying-chun , Yuan Yi-jie , Li Dan
Published: January 2008

Brenner-LJ potential is adopted to describe the interactivity between diamond and C36 cluster, and the deposition mechanism of multi-C36 on the diamond surface is researched by molecular dynamics simulation. Through simulative experiments the incident energy, incident point, incident posture, incident angle and other factors are analyzed. Studies discover that the minimal deposition threshold is 20 eV and the maximum is 60 eV with the different incident point locations and incident postures of C36 clusters. When the incident angle is not over 60, C36 may roll or slip to the region of smaller bonding energy and then bond. So the bonding probability is raised. Research results show that when incident angle is between 0 and 20 and incident energy range is from 30 eV to 60 eV, it is the optimal condition of single C36 cluster deposition on diamond (100) crystal plane.
Surface Formation of Single Silicon Wafer Polished with Nano-sized Al2O3 Powders
Authors: Sun Yu-li , Zuo Dun-wen , Zhu Yong-wei , Wang Min
Published: January 2008

Ice polishing single silicon wafers with nano-sized Al2O3 abrasives can be known as ice fixed abrasives chemical mechanical polishing (IFA-CMP). TAn abrasive slurry was made of nano-sized Al2O3 particles dispersed in de-ionized water with a surfactant and the slurry was frozen to form an ice polishing pad. Then polishing tests of blanket silicon wafers with the above ice polishing pad were carried out. The morphologies and surface roughness of the polished silicon wafers were observed and examined on an atomic force microscope. The subsurface damage was assessed by means of cross-section transmission electron microscopy. The surface chemical constituents of the polished silicon wafers were characterized using X-ray photoelectron spectroscopy in order to gain insight into the chemical mechanisms in the process. Scratch resistance of the single silicon wafer was measured by nanoscratching using a nanoindenter to explore the mechanical removal mechanism. The results show that a super smooth surface with an average roughness of 0.367 nm is obtained within 1000 nm 1000 nm and there is a perfect silicon diamond structure without any microcracks in the subsurface. The removal of material is dominated by the coactions of ductile regime machining and chemical corrosion. In the end, a model of material removal of IFA-CMP is built.
Chemomechanical Production of Functional Structure on Silicon Surfaces
Authors: Shi Li-qiu , Yan Yong-da , Wang Feng , Sun Tao , Dong Shen
Published: January 2008

The chemomechanical method was used to scribe the silicon surface with a diamond-tipped instrument in the presence of aryldiazonium salt, the silicon and the arenes was connected with covalent bond, and realize simultaneously functionalizing and patterning silicon. This provided experiment basis for building nano-scale functional structure. At first we scribe the silicon with a diamond-tipped instrument in the atmospheric, and get the micro-structure with better surface quality, which was then used as substrate for the next functionalizing and patterning silicon. By the silicon's controlled self-assembly experiments in the solution, the cutting speed, cutting assembly time in accord with the self-assembled monolayers' quality (SAMs), and more parameters suitable for the film growth are obtained. X-ray photoelectron spectroscopy was used to test the self-assembly monolayers, and atomic force microscopy as well as scanning electron microscopy to characterize the surface morphology. Results show that this method can efficiently achieve simultaneously functionalizing and patterning silicon. We also connect the carbon nanotubes to the SAMs, and charatrerize the surface with AFM. This will provide experimental basis for the further study using SAMs to function silicon surface.
Resistivity and Field Electron Emission of Nanowires Formed by Electron Beam Induced Chemical Vapor Deposition
Authors: Che Ren-chao , Liang Chong-yun , Zhou Xin-gui , Shi Hong-long , Feng Jian , Li Jian-qi
Published: January 2008

Self-standing iron nanowires were fabricated at the apex of a tungsten needle tip by electron beam induced deposition. This sharp needle tip which adhered to the nanowire can be moved with a stepping motor and piezo-driving device, and was attached inside a specially designed transmission electron microscope specimen holder. A copper conductor substrate, with which the approaching nanowires will build up a closed electric circuit, was set on the holder. The tungsten needle tip accompanied with the EBICVD nanowires made contact with the substrate and then a voltage was applied between the two electrodes. Resistivity values of the examined nanowires, by a devised Lock-in-Amplifier circuit, range from 0.1 m to 103 m. Our investigation might have implications in the fabrication and characterization of nano-electronics device. Precursor with phenanthrene (C4H10) was used and the deposition experiment was done using a scanning electron microscope at room temperature. It was found that the surface structure at the top of the nanorod, such as a small protrusion within only several nanometers scale, has significant influence on the field emission property. An emission current of several tens of nano-ampere flowing through this nanorod could induce resistance heating. In several minutes, this thermal energy could transform the original amorphous carbon into a graphite-like structure embedded with fullerenes. The turn-on voltage of the graphite-like nanorod was about 11 V less than that of the original amorphous case.
Field Emission Properties of Multi-walled Carbon Nanotubes Grown on Silicon Nanoporous Pillar Array
Authors: Jiang Wei-fen , Li Long-yu , Xiao Shun-hua , Yang Xiao-hui , Jia Min , Li Xin-jian
Published: January 2008

Multi-walled carbon nanotubes (CNTs) were grown on a silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Surface morphologies and microstructure of the resultant were studied by a field emission scanning electron microscope, Raman spectrum, transmission electron microscope, and high-resolution transmission electron microscopy. The composition of samples was determined by energy dispersive X-ray spectroscopy (EDS). The results showed that a great deal of CNTs, with diameter in the range of 2070 nm, incorporated with Si-NPA and a large scale nest array of CNTs/Si-NPA (NACNT/Si-NPA) was formed. EDS analysis showed that the composition of carbon nanotubes was carbon. Field emission measurements showed that a current density of 5 mA/cm2 was obtained at an electric field of 4.26 V/m, with a turn-on field of 1.3 V/m. The enhancement factor calculated according to the Fowler-Nordheim theory was 11,000. This excellent field emission performance is attributed to the unique structure and morphology of NACNT/Si-NPA, especially the formation of a nest-shaped carbon nanotube array. A schematic drawing that illustrates the experimental configuration is given. These results indicate that NACNT/Si-NPA might be an ideal candidate cathode for potential applications in flat panel displays.
Hydrothermal Preparation and Oxygen Storage Capacity of Nano CeO2-based Materials
Authors: Liu Li-li , Zhang Mei , Guo Min , Wang Xi-dong
Published: January 2008

Nano-powders of NiO-CeO2 and Bi2O3-CeO2 binary compounds for a promoter in the automotive three-way catalysts were synthesized by hydrothermal method. The X-ray diffraction result showed that the average particle size was in the range of 1112 nm, which was correspondence to the high-resolution transmission electron microscopy result that the average particle size was about 12 nm. The specific surface area of the NiO-CeO2 binary compounds was in the range of 5475 m2/g. Also the average particle size of the Bi2O3-CeO2 binary compounds was in the range of 811 nm. The oxygen storage capacity of the NiO-CeO2 and Bi2O3-CeO2 binary compounds was investigated under reduction and oxidation conditions. When the Ni and Bi concentration in CeO2 was up to 30%, the OSC values reached 2465 and 2560 molO/g separately, which indicated that NiO and Bi2O3 compounded CeO2 materials have fine catalysis activity than other cations doped CeO2-based materials and appear to be very promising for practical applications such as OSC materials.
Photocatalytic Degradation of Acetaldehyde on Mesoporous TiO2: Effects of Surface Area and Crystallinity on the Photocatalytic Activity
Authors: Fan Xiao-xing , Yu Tao , Zhang Li-zhi , Chen Xin-yi , Zou Zhi-gang
Published: January 2008

Mesoporous TiO2 powder and films with worm-like channels were synthesized by an evaporation-induced self-assembly approach. The as-prepared samples were calcined at different temperature to investigate the effect of calcined temperature on the mesostructure and the photocatalytic activity. Acetaldehyde photodegradation in gas phase was employed to evaluate the photocatalytic activity of mesoporous TiO2. Results showed that all the calcined powder samples exhibited higher photocatalytic activities than that of Degussa P25. The sample calcined at 400C, which showed higher activity than other samples, possessed a homogeneous pore diameter of about 6.0 nm and an 11.0 nm crystalline anatase pore wall, as well as large surface area of 117 m2/g. It was speculated that two factors of surface area and crystallinity affected the photocatalytic activity of mesoporous TiO2 photocatalyst. The mesoporous TiO2 films fabricated by spin-coating also had high photocatalytic activities.
Microstructure and Magnetic Properties of Ag/Fe/Ag Pseudo-Sandwich Nanogranular Films
Authors: Peng Yan , Hu Yan-ying , Li Yao-peng , Sun Hui-yuan
Published: January 2008

Nanogranular Ag/Fe/Ag films were prepared by magnetron sputtering from a silver and an iron target onto glass substrates at room temperature and subsequent in situ annealing. The structural and magnetic properties of the films were investigated as a function of silver layer thickness and annealing temperature. X-ray diffraction shows the Fe(110) peak is formed in all the samples. Vibrating sample magnetometer measurements indicate that the magnetic moments lie well perpendicular to the film plane. Coercivity reaches the maximum in the sample annealed at 500C for 30 min with 3 nm Ag layer. A scanning probe microscope was used to scan surface morphology and magnetic domain structures. In as-deposited samples the average grain size and the average roughness is smaller than that the annealing samples. After annealing, the grain size is larger and the contrast of domains increases, but the domain size becomes smaller.
Preparation and Absorption Properties in Near Infrared Wavelength of Carbon Nanotubes/Acrylate Coatings
Authors: Sun Hui-min , Shen Xiao-dong , Cui Sheng , Xu Na
Published: January 2008

Carbon nanotubes can be used as absorbent materials at the near infared range. In this study, carbon nanotube was treated with surfactant to prevent aggregation, and the acrylate coating of the carbon nanotube was prepared with the carbon nanotube solution and the near infrared reflection properties of the coating were studied. A series of factors influencing the reflectivity of carbon nanotubes/acrylate coatings at 930 nm, such as PVC concentration, the kinds and concentration of the surfactant and size range of the carbon nanotube, were studied. Based on these, the coating procedure was optimized and the carbon nanotubes/acrylate coating was prepared with good absorption properties. The reflectivity is under 0.1% of the coatings and its transmission is below 1.0% at near infrared wavelength of 840980 nm.
Structure Characterization of CuCl2-FeCl3-H2SO4 Graphite Intercalation Compounds
Authors: Liang Chong-yun , Che Ren-chao , Tian Huan-fang , Shi Hong-long , Li Jian-qi
Published: January 2008

Graphite intercalation compounds with CuCl2-FeCl3-H2SO4 were synthesized via a hydrothermal treatment at 150C and exfoliation method. The structure and composition of these graphite intercalation compounds were analyzed by means of X-ray diffraction, energy dispersive X-ray and high-resolution transmission electron microscopy. The results demonstrate that the CuCl2-FeCl3-H2SO4 molecules were successfully intercalated into the interlayer of the graphite sheets. The temperature dependence of magnetization was measured from 5 K to 300 K. Two antiferromagnetic transitions of the graphite intercalation compounds were observed at low temperatures. The critical transition temperatures are estimated to be about 50 and 102 K. The related magnetic properties are discussed briefly.
Enhanced Photoelectric Conversion of Dye-sensitized Solar Cell by Addition of Inorganic Particles
Authors: Li Bing , Cheng Ping , Deng Chang-sheng
Published: January 2008

Electrochemical impedance spectroscopy and cyclic voltammetry were used to investigate the effect of various inorganic particles, including titania, alumina, zirconia with particle sizes ranging from nano- to micro-meter on electrochemical properties of the electrolyte used in dye-sensitized solar cell. Adding inorganic particles could improve the ionic transport of I3 in the electrolyte and reduce the electrolyte-electrode transfer resistance, leading to an improvement of the photoelectric conversion efficiency of the devices. It was proposed that the improvement could be attributed to the interfacial effect between the inorganic particles and the electrolyte; ionic conduction paths formed between the solid particles facilitate the diffusion of the I3 in the electrolyte and improve the connection between the electrolyte and the electrode. Combined with a less volatile solvent system and a proper amount of the inorganic particles as the additive, an overall efficiency of 5.5% for the DSC (1 cm2) with P25 (10%) under 100 mW/cm2 at room temperature was achieved, an improvement of 51% over that without the oxide additive.
Spred1 and TESK1—Two New Interaction Partners of the Kinase MARKK/TAO1 That Link the Microtubule and Actin Cytoskeleton
Authors: Johne Cindy , Matenia Dorthe , Li Xiao-yu , Timm Thomas , Balusamy Kiruthiga , Mandelkow Eva-Maria
Published: January 2008

The signaling from MARKK/TAO1 to the MAP/microtubule affinity-regulating kinase MARK/Par1 to phosphorylated microtubule associated proteins (MAPs) renders microtubules dynamic and plays a role in neurite outgrowth or polarity development. Because hyperphosphorylation of Tau at MARK target sites is a hallmark of Alzheimer neurodegeneration, we searched for upstream regulators by the yeast two-hybrid approach and identified two new interaction partners of MARKK, the regulatory Sprouty-related protein with EVH-1 domain1 (Spred1) and the testis-specific protein kinase (TESK1). Spred1-MARKK binding has no effect on the activity of MARKK; therefore, it does not change microtubule (MT) stability. Spred1-TESK1 binding causes inhibition of TESK1. Because TESK1 can phosphorylate cofilin and thus stabilizes F-actin stress fibers, the inhibition of TESK1 by Spred1 makes F-actin fibers dynamic. A third element in this interaction triangle is that TESK1 binds to and inhibits MARKK. Thus, in Chinese hamster ovary (CHO) cells the elevation of MARKK results in MT disruption (via activation of MARK/Par1 and phosphorylation of MAPs), but this can be blocked by TESK1. Similarly, enhanced TESK1 activity results in increased stress fibers (via phospho-cofilin), but this can be blocked by elevating Spred1. Thus, the three-way interaction between Spred1, MARKK, and TESK1 represents a pathway that links regulation of both the microtubule- and F-actin cytoskeleton.
Disruption of c-Jun Reduces Cellular Migration and Invasion through Inhibition of c-Src and Hyperactivation of ROCK II Kinase
Authors: Jiao Xuanmao , Katiyar Sanjay , Liu Manran , Mueller Susette C. , Lisanti Michael P. , Li Anping , Pestell Timothy G. , Wu Kongming , Ju Xiaoming , Li Zhiping , Wagner Erwin F. , Takeya Tatsuo , Wang Chenguang , Pestell Richard G.
Published: January 2008

The spread of metastatic tumors to different organs is associated with poor prognosis. The metastatic process requires migration and cellular invasion. The protooncogene c-jun encodes the founding member of the activator protein-1 family and is required for cellular proliferation and DNA synthesis in response to oncogenic signals and plays an essential role in chemical carcinogenesis. The role of c-Jun in cellular invasion remains to be defined. Genetic deletion of c-Jun in transgenic mice is embryonic lethal; therefore, transgenic mice encoding a c-Jun gene flanked by LoxP sites (c-junf/f) were used. c-jun gene deletion reduced c-Src expression, hyperactivated ROCK II signaling, and reduced cellular polarity, migration, and invasiveness. c-Jun increased c-Src mRNA abundance and c-Src promoter activity involving an AP-1 site in the c-Src promoter. Transduction of c-jun−/−cells with either c-Jun or c-Src retroviral expression systems restored the defective cellular migration of c-jun−/−cells. As c-Src is a critical component of pathways regulating proliferation, survival, and metastasis, the induction of c-Src abundance, by c-Jun, provides a novel mechanism of cooperative signaling in cellular invasion.
UME6, a Novel Filament-specific Regulator ofCandida albicansHyphal Extension and Virulence
Authors: Banerjee Mohua , Thompson Delma S. , Lazzell Anna , Carlisle Patricia L. , Pierce Christopher , Monteagudo Carlos , López-Ribot José L. , Kadosh David
Published: January 2008

The specific ability of the major human fungal pathogen Candida albicans, as well as many other pathogenic fungi, to extend initial short filaments (germ tubes) into elongated hyphal filaments is important for a variety of virulence-related processes. However, the molecular mechanisms that control hyphal extension have remained poorly understood for many years. We report the identification of a novel C. albicans transcriptional regulator, UME6, which is induced in response to multiple host environmental cues and is specifically important for hyphal extension. Although capable of forming germ tubes, the ume6Δ/ume6Δ mutant exhibits a clear defect in hyphal extension both in vitro and during infection in vivo and is attenuated for virulence in a mouse model of systemic candidiasis. We also show that UME6 is an important downstream component of both the RFG1-TUP1 and NRG1-TUP1 filamentous growth regulatory pathways, and we provide evidence to suggest that Nrg1 and Ume6 function together by a negative feedback loop to control the level and duration of filament-specific gene expression in response to inducing conditions. Our results suggest that hyphal extension is controlled by a specific transcriptional regulatory mechanism and is correlated with the maintenance of high-level expression of genes in the C. albicans filamentous growth program.
Precise score for the prediction of peptides cleaved by the proteasome
Authors: Ginodi Ido , Vider-Shalit Tal , Tsaban Lea , Louzoun Yoram
Published: January 2008

Motivation: An 8–10mer can become a cytotoxic T lymphocyte epitope only if it is cleaved by the proteasome, transported by TAP and presented by MHC-I molecules. Thus most of the epitopes presented to cytotoxic T cells in the context of MHC-I molecules are products of intracellular proteasomal cleavage. These products are not random, as peptide production is a function of the precise sequence of the proteins processed by the proteasome.

Results: We have developed a score for the probability that a given peptide results from proteasomal cleavage. High scoring peptides are those that are cleaved in their extremities and not in their center, while low scoring peptides are either cleaved in their centers or not cleaved in their extremities. The current work differs from most previous works, in that it determines the production probability of an entire peptide, rather than trying to predict specific cleavage sites. We further present different score functions for the constitutive and the immunoproteasome. Our results were validated to have low error levels against multiple epitope databases. We provide here a novel computational tool and a website to use it—http://peptibase.cs.biu.ac.il/PepCleave_II/ to assess the probability that a given peptide indeed results from proteasomal cleavage.

Contact:  louzouy@math.biu.ac.il

Supplementary information: Supplementary data are available at Bioinformatics online.
Observation of multiple folding pathways of β-hairpin trpzip2 from independent continuous folding trajectories
Authors: Chen Changjun , Xiao Yi
Published: January 2008

Motivation: After 10-year investigations, the folding mechanisms of β-hairpins are still under debate. Experiments strongly support zip-out pathway, while most simulations prefer the hydrophobic collapse model (including middle-out and zip-in pathways). In this article, we show that all pathways can occur during the folding of β-hairpins but with different probabilities. The zip-out pathway is the most probable one. This is in agreement with the experimental results. We came to our conclusions by 38 100-ns room-temperature all-atom molecular dynamics simulations of the β-hairpin trpzip2. Our results may help to clarify the inconsistencies in the current pictures of β-hairpin folding mechanisms.

Contact:  yxiao@mail.hust.edu.cn

Supplementary information: Supplementary data are available at Bioinformatics online.
Sliding-induced adhesion of stiff polymer microfibre arrays. II. Microscale behaviour
Authors: Schubert Bryan , Lee Jongho , Majidi Carmel , Fearing Ronald S
Published: January 2008

The adhesive pads of geckos provide control of normal adhesive force by controlling the applied shear force. This frictional adhesion effect is one of the key principles used for rapid detachment in animals running up vertical surfaces. We developed polypropylene microfibre arrays composed of vertical, 0.3 μm radius fibres with elastic modulus of 1 GPa which show this effect for the first time using a stiff polymer. In the absence of shear forces, these fibres show minimal normal adhesion. However, sliding parallel to the substrate with a spherical probe produces a frictional adhesion effect which is not seen in the flat control. A cantilever model for the fibres and the spherical probe indicates a strong dependence on the initial fibre angle. A novel feature of the microfibre arrays is that adhesion improves with use. Repeated shearing of fibres temporarily increases maximum shear and pull-off forces.
General relationships between pressure, weight and mass of a hydrostatic fluid
Authors: Ambaum Maarten H.P
Published: January 2008

In curved geometries the hydrostatic pressure in a fluid does not equal the weight per unit area of the fluid above it. General weight–pressure and mass–pressure relationships for hydrostatic fluids in any geometry are derived. As an example of the mass–pressure relationship, we find a geometric reduction in surface pressure as large as 5 mbar on Earth and 39 mbar on Titan. We also present a thermodynamic interpretation of the geometric correction which, as a corollary, provides an independent proof of the hydrostatic relationship for general geometries.
Swingin' in the rain: condition dependence and sexual selection in a capricious world
Authors: Cockburn Andrew , Osmond Helen L , Double Michael C
Published: January 2008

Signals used in mate attraction are predicted to be highly condition dependent, and thus should be sensitive to environmental contributions to condition. However, the effects of temporal fluctuations in the environment on sexual selection in long-lived animals have been largely ignored. Female superb fairy-wrens,
Malurus cyaneus
, use the time that males moult into nuptial plumage prior to the onset of the breeding season to distinguish between the extra-group sires that dominate paternity. Although moult varies predictably with age, and shows marked differences between males, the phenotypic distribution also changes radically with climate; so after dry summers few males can attempt early moult. We use the recently introduced de-lifing technique to examine sexual selection gradients over 15 years of selection. Overall, there was strong evidence of directional sexual selection for early moult. However, sexual selection was much stronger when the conditions were favourable (rainfall was high), and selection was undetectable in some years. The contribution of early moulting males to population growth increased when many males moulted early, decreased when early moulting males suffered disproportionate mortality and decreased when females lacked subordinate helpers, forcing them to cede paternity to their social partner. These data suggest that short-term and laboratory studies of mate choice and sexual selection may misrepresent or underestimate the complexity of the sexual selection landscape.
Natural and sexual selection against hybrid flycatchers
Authors: Svedin Nina , Wiley Chris , Veen Thor , Gustafsson Lars , Qvarnström Anna
Published: January 2008

While sexual selection is generally assumed to quickly cause or strengthen prezygotic barriers between sister species, its role in causing postzygotic isolation, through the unattractiveness of intermediate hybrids, is less often examined. Combining 24 years of pedigree data and recently developed species-specific molecular markers from collared (Ficedula albicollis) and pied (Ficedula hypoleuca) flycatchers and their hybrids, we were able to quantify all key components of fitness. To disentangle the relative role of natural and sexual selection acting on F1 hybrid flycatchers, we estimated various fitness components, which when combined represent the total lifetime reproductive success of F1 hybrids, and then compared the different fitness components of F1 hybrids to that of collared flycatchers. Female hybrid flycatchers are sterile, with natural selection being the selective force involved, but male hybrids mainly experienced a reduction in fitness through sexual selection (decreased pairing success and increased rate of being cuckolded). To disentangle the role of sexual selection against male hybrids from a possible effect of genetic incompatibility (on the rate of being cuckolded), we compared male hybrids with pure-bred males expressing intermediate plumage characters. Given that sexual selection against male hybrids is a result of their intermediate plumage, we expect these two groups of males to have a similar fitness reduction. Alternatively, hybrids have reduced fitness owing to genetic incompatibility, in which case their fitness should be lower than that of the intermediate pure-bred males. We conclude that sexual selection against male hybrids accounts for approximately 75% of the reduction in their fitness. We discuss how natural and sexual selection against hybrids may have different implications for speciation and conclude that reinforcement of reproductive barriers may be more likely when there is sexual selection against hybrids.
Keeping up with a warming world; assessing the rate of adaptation to climate change
Authors: Visser Marcel E
Published: January 2008

The pivotal question in the debate on the ecological effects of climate change is whether species will be able to adapt fast enough to keep up with their changing environment. If we establish the maximal rate of adaptation, this will set an upper limit to the rate at which temperatures can increase without loss of biodiversity.

The rate of adaptation will primarily be set by the rate of microevolution since (i) phenotypic plasticity alone is not sufficient as reaction norms will no longer be adaptive and hence microevolution on the reaction norm is needed, (ii) learning will be favourable to the individual but cannot be passed on to the next generations, (iii) maternal effects may play a role but, as with other forms of phenotypic plasticity, the response of offspring to the maternal cues will no longer be adaptive in a changing environment, and (iv) adaptation via immigration of individuals with genotypes adapted to warmer environments also involves microevolution as these genotypes are better adapted in terms of temperature, but not in terms of, for instance, photoperiod.

Long-term studies on wild populations with individually known animals play an essential role in detecting and understanding the temporal trends in life-history traits, and to estimate the heritability of, and selection pressures on, life-history traits. However, additional measurements on other trophic levels and on the mechanisms underlying phenotypic plasticity are needed to predict the rate of microevolution, especially under changing conditions.

Using this knowledge on heritability of, and selection on, life-history traits, in combination with climate scenarios, we will be able to predict the rate of adaptation for different climate scenarios. The final step is to use ecoevolutionary dynamical models to make the link to population viability and from there to biodiversity loss for those scenarios where the rate of adaptation is insufficient.
Quantitative genetics and sex-specific selection on sexually dimorphic traits in bighorn sheep
Authors: Poissant Jocelyn , Wilson Alastair J , Festa-Bianchet Marco , Hogg John T , Coltman David W
Published: January 2008

Sexual conflict at loci influencing traits shared between the sexes occurs when sex-specific selection pressures are antagonistic relative to the genetic correlation between the sexes. To assess whether there is sexual conflict over shared traits, we estimated heritability and intersexual genetic correlations for highly sexually dimorphic traits (horn volume and body mass) in a wild population of bighorn sheep (
Ovis canadensis
) and quantified sex-specific selection using estimates of longevity and lifetime reproductive success. Body mass and horn volume showed significant additive genetic variance in both sexes, and intersexual genetic correlations were 0.24±0.28 for horn volume and 0.63±0.30 for body mass. For horn volume, selection coefficients did not significantly differ from zero in either sex. For body weight, selection coefficients were positive in females but did not differ from zero in males. The absence of detectable sexually antagonistic selection suggests that currently there are no sexual conflicts at loci influencing horn volume and body mass.
Estimation of quantitative genetic parameters
Authors: Thompson Robin
Published: January 2008

This paper gives a short review of the development of genetic parameter estimation over the last 40 years. The need to analyse genetic processes in both animal selection experiments and animal breeding improvement programmes motivated the majority of this work. The usage of animal model in conjunction with residual maximum likelihood (REML) techniques for mixed models has revolutionized the methods. These methods to estimate quantitative genetic parameters have recently been advocated for use in evolutionary studies of natural populations. Therefore, it is perhaps timely to discuss the development of REML methods and their application to the analysis of artificial selection experiments and breeding programmes in animals. This should give extra insight into the methods and hopefully lead to synergy between both the areas.
Notch Effect on Low Cycle Fatigue of Sn–3.5Ag Solder
Authors: Nozaki Mineo , Sakane Masao , Tsukada Yutaka
Published: January 2008

This paper studies the notch effect on low cycle fatigue of Sn–3.5Ag solder. Strain controlled push-pull low cycle fatigue tests were carried out using three circumferential notched specimens at 313K. Cycles to crack initiation were measured by an a.c. potential method, and cycles to failure and for crack propagation were also determined in experiments. Cycles to failure, to crack initiation, and for propagation decreased with elastic stress concentration factor but cycles to crack initiation were most sharply reduced with elastic stress concentration factor. Prediction methods of cycles to crack initiation, for propagation, and to failure were discussed from the data fitting and the local strain approach utilizing finite element analysis.