bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of uniaxial stress on stimulated terahertz emission from phosphor and antimony donors in silicon
Authors: Zhukavin R. Kh. , Tsyplenkov V. V. , Kovalevsky K. A. , Shastin V. N. , Pavlov S. G. , Böttger U. , Hübers H.-W. , Riemann H. , Abrosimov N. V. , Nötzel N.
Published: February 2007

The effect of uniaxial stress on terahertz stimulated emission from phosphor and antimony donors in silicon excited by CO2 laser radiation was studied. The laser action originates from 2p0→1s(T2) intracenter transitions. A compressive force applied to the silicon crystal decreases the laser threshold by one order of magnitude. The output power depends nonmonotonically on the stress, while the emission frequency does not change. The results are explained by changes of the donor electronic structure, which do not affect the energy gap between the laser states, and a resonant interaction with acoustic f-TA and g-TA phonons that disappears with increasing stress.
Modeling of plasma-controlled evaporation and surface condensation of Al induced by 1.06 and 0.248μm laser radiations
Authors: Mazhukin V. I. , Nossov V. V. , Smurov I.
Published: February 2007

Phase transition on the surface of an aluminum target and vapor plasma induced by laser irradiation in the nanosecond regime at the wavelengths of 1.06μm in the infrared range and 0.248μm in the ultraviolet range with an intensity of 108–109W∕cm2 in vacuum are analyzed. Special attention is paid to the wavelength dependence of the observed phenomena and the non-one-dimensional effects caused by the nonuniform (Gaussian) laser intensity distribution and the lateral expansion of the plasma plume. A transient two-dimensional model is used which includes conductive heat transfer in the condensed phase, radiative gas dynamics, and laser radiation transfer in the plasma as well as surface evaporation and back condensation at the phase interface. It was shown that distinctions in phase transition dynamics for the 1.06 and 0.248μm radiations result from essentially different characteristics of the laser-induced plasmas. For the 1.06μm radiation, evaporation stops after the formation of hot optically thick plasma, can occasionally resume at a later stage of the pulse, and proceeds nonuniformly in the spot area, and the major contribution to the mass removal occurs in the outer part of the irradiated region. Plasma induced by the 0.248μm laser is colder and partially transparent since it transmits 30%–70% of the incident radiation; therefore evaporation does not stop but continues in the subsonic regime with the Mach number of about 0.1. The amount of evaporated matter that condenses back to the surface is as high as 15%–20% and less than 10% for the 1.06 and 0.248μm radiations, respectively. For a beam radius smaller than ∼100μm, the screening and retarding effect of the plasma weakens because of the lateral expansion, thickness of the removed layer increases, and condensation after the end of the pulse is not observed. Comparison of the numerical and experimental results on the removed layer thickness has shown, in particular, the importance of accounting for the plasma effect to predict the correct trends for radiation intensity and beam radius.
Dielectric and ferroelectric properties of BaTiO3–(Na1∕4Bi3∕4)(Mg1∕4Ti3∕4)O3 ceramics
Authors: Wang Xiaoli , Cao Wenjuan
Published: February 2007

Perovskite ceramics (1−x)BaTiO3–x(Na1∕4Bi3∕4)(Mg1∕4Ti3∕4)O3 (x⩽0.10) were prepared using solid-state reaction. The permittivity peak of the compositions x=0.08 and 0.10 is saddle backed. The high turning temperature fixes at ∼400K and is the Burns temperature TB of the samples. The low turning point decreases with increasing content of (Na1∕4Bi3∕4)(Mg1∕4Ti3∕4)O3 and is associated with transformation between domains and polar nanoregions. The P-E relationship indicates that the permittivity in the saddle-backed region for composition x=0.10 is quasilinear when E<2MV∕m. The behavior suggests a possible way for developing linear dielectrics with very high permittivity.
Ground and excited state transitions in as-grown Ga0.64In0.36N0.046As0.954 quantum wells studied by contactless electroreflectance
Authors: Kudrawiec Robert , Gladysiewicz Marta , Misiewicz Jan , Ishikawa Fumitaro , Ploog Klaus H.
Published: February 2007

The optical transitions of as-grown Ga0.64In0.36N0.046As0.954 multiple quantum wells grown at the low temperature of 375°C were studied by contactless electroreflectance (CER). The investigation was carried out at room temperature for a set of samples having quantum well (QW) widths ranging from 3.9to8.1nm. The ground and the excited state transitions were clearly observed in CER spectra (the ground state transition was observed at the wavelength of 1.9μm for the 8.1nm wide QW). The experimental QW transition energies were compared with theoretical predictions based on an effective mass formalism model. Good agreement between experimental data and theoretical calculations has been obtained assuming that the conduction band offset for GaInNAs∕GaAs interface is 80% and the electron effective mass is 0.09m0.
Use of anisotropic laser etching to the top n-GaN layer to alleviate current-crowding effect in vertical-structured GaN-based light-emitting diodes
Authors: Chen Tron-Min , Wang Shui-Jinn , Uang Kai-Ming , Chen Shiue-Lung , Tsai Wei-Chih , Lee Wei-Chi , Tsai Ching-Chung
Published: February 2007

To equalize the resistance of all possible current paths in regular vertical-conducting metal-substrate GaN-based light-emitting diodes (VM-LEDs), an anisotropic laser etching to the surface layer (n-GaN) of 40mil VM-LEDs for improving light emission uniformity and light output power is proposed and demonstrated. The feasibility of the proposed scheme was verified by current and light emission distribution as well as light extraction rate simulations. In conjunction with a nonuniform excimer laser beam irradiation through a mask and rotation of the epitaxy wafer, VM-LEDs with a concave-surface n-GaN layer were also fabricated. Typical improvement in light output power by 38%–26% at an injection current of 350mA as compared to the one without anisotropic etching has been obtained.
Enhanced NO2 selectivity of hybrid poly(3-hexylthiophene): ZnO-nanowire thin films
Authors: Saxena Vibha , Aswal D. K. , Kaur Manmeet , Koiry S. P. , Gupta S. K. , Yakhmi J. V. , Kshirsagar R. J. , Deshpande S. K.
Published: February 2007

Sensing characteristics of the drop-cast thin films of poly(3-hexylthiophene) (P3HT), ZnO nanowires, and P3HT:ZnO-nanowire hybrids with different compositions have been studied for various gases, namely, NO2, H2S, NH3, CH4, and CO. At room temperature, pure P3HT and ZnO-nanowire films were highly sensitive to NO2 and H2S, moderately sensitive to CO, and nearly insensitive to NH3 and CH4. P3HT:ZnO-nanowire hybrid films, with increasing ZnO-nanowire content, exhibited gradual enhancement in NO2 sensitivity, while reducing sensitivity for H2S. P3HT:ZnO-nanowire (1:1 ratio by weight) films were found to be highly selective for NO2. Plausible mechanisms explaining the enhanced NO2 selectivity by hybrid films are discussed.
Photoluminescence study of an ultrathin strained silicon on insulator layer
Authors: Munguía J. , Bremond G. , de la Torre J. , Bluet J.-M.
Published: February 2007

Low temperature photoluminescence has been performed in order to analyze the strain effect on the Si band structure for an 8 nm thick tensile strained silicon layer on insulator. The authors show three phonon assisted optical transitions related to the strained silicon top layer at 0.923, 0.983, and 1.022eV. The 0.983eV line of the TO phonon assisted transition corresponds to a 115meV strain induced band gap shrinkage at Δ point which agrees with the calculated values of strained silicon band gap.
Raman study of thermochromic phase transition in tungsten trioxide nanowires
Authors: Lu Dong Yu , Chen Jian , Chen Huan Jun , Gong Li , Deng Shao Zhi , Xu Ning Sheng , Liu Yu Long
Published: February 2007

Tungsten trioxide (WO3) nanowires were synthesized by thermal evaporation of tungsten powder in two steps: tungsten suboxide (WO3−x) nanowires were synthesized, and then oxidized in O2 ambient and transformed into WO3 nanowires. Raman spectroscopy was applied to study the thermochromic phase transition of one-dimensional WO3 nanowires. From the temperature dependence of the characteristic mode at 33cm−1 in WO3, the phase transition temperature was determined. It was found that the phase transition of WO3 nanowires was reversible and the phase transition temperatures were even lower than that of WO3 nanopowder.
Room temperature p-n ZnO blue-violet light-emitting diodes
Authors: Wei Z. P. , Lu Y. M. , Shen D. Z. , Zhang Z. Z. , Yao B. , Li B. H. , Zhang J. Y. , Zhao D. X. , Fan X. W. , Tang Z. K.
Published: February 2007

ZnO p-n junction light-emitting diodes (LEDs) were fabricated on c-plane Al2O3 substrates by plasma-assisted molecular beam epitaxy. Gas mixture of N2 and O2 was used as the p-type dopant, by which the double-donor doping of N2(O) can be avoided significantly. The fabricated p-type ZnO layers have a higher hole density and carrier mobility. The LEDs showed a very good rectification characteristic with a low threshold voltage of 4.0V even at a temperature above 300K. The LEDs can even emit intensive electroluminescence in the blue-violet region at the temperature of 350K. The blue-violet emission was attributed to the donor-acceptor pair recombination at the p-type layer of the LED.
Efficient focusing of hard x rays to 25nm by a total reflection mirror
Authors: Mimura Hidekazu , Yumoto Hirokatsu , Matsuyama Satoshi , Sano Yasuhisa , Yamamura Kazuya , Mori Yuzo , Yabashi Makina , Nishino Yoshinori , Tamasaku Kenji , Ishikawa Tetsuya , Yamauchi Kazuto
Published: February 2007

Nanofocused x rays are indispensable because they can provide high spatial resolution and high sensitivity for x-ray nanoscopy/spectroscopy. A focusing system using total reflection mirrors is one of the most promising methods for producing nanofocused x rays due to its high efficiency and energy-tunable focusing. The authors have developed a fabrication system for hard x-ray mirrors by developing elastic emission machining, microstitching interferometry, and relative angle determinable stitching interferometry. By using an ultraprecisely figured mirror, they realized hard x-ray line focusing with a beam width of 25nm at 15keV. The focusing test was performed at the 1-km-long beamline of SPring-8.
Impact of Ni-silicide grain orientation on the strain and stress fields induced in patterned silicon
Authors: Torregiani C. , Maex K. , Benedetti A. , Bender H. , Van Houtte P. , Pawlak B. J. , Kittl J. A.
Published: February 2007

The relationship between silicide grain orientation and strain/stress induced in patterned silicon has been experimentally investigated for structures formed by NiSi lines spaced by SiO2∕Si3N4 stacks. The strain and stress fields exhibit a significant asymmetry that has been attributed to the difference in the orientations of silicide grains at the two sides of the stacks. Finite element simulations support and complete the study, indicating that NiSi orientation can strongly affect the stress profile in the silicon between two silicide lines. These results are useful to understand at a fundamental level the buildup of stress and strain in actual transistors.
Time-resolved visualization of the heat flow in VO2∕Al2O3 films
Authors: Lee J. S. , Ortolani M. , Schade U. , Chang Y. J. , Noh T. W.
Published: February 2007

The authors performed resistance switching of a VO2 film grown on the Al2O3 substrate by applying electric pulses. As a consequence, Joule heat of about 1W has been induced in a 15×50μm2 area between the two electrodes. Using synchrotron-based infrared microspectroscopy, the authors mapped the propagation of Joule heat around the electrodes with a micrometric spatial resolution and in a submicrosecond time scale. They found that the experimental observations are well described by the Fourier law of heat conduction demonstrating the possibility of local temperature control in a micrometric length scale.
Geometry of phenylene motion in polycarbonate from NMR spectroscopy and neutron scattering
Authors: Graf Robert , Ewen Bernd , Spiess Hans Wolfgang
Published: February 2007

In view of the importance of molecular dynamics in condensed matter both time scale and geometry of such processes should be determined experimentally. Whereas many techniques are available for the former, only NMR spectroscopy and neutron scattering can provide detailed information on the latter. Because of the different time scales of the dynamics, which the two techniques can detect best, direct comparisons of probing the geometry of the dynamics in the same system are scarce. Here we present such a comparison for the complex rotational motion of the phenylene groups in amorphous polycarbonate based on published H2 NMR and newly recorded C13 NMR data covering a wide temperature range, and recent quasielastic neutron scattering (QENS) data. We show that the results of the two techniques are in remarkable agreement, provided the data are consistently analyzed. No evidence is found for additional motions characterized by 90° flips recently deduced from QENS data alone. Instead, the phenylene motion in the glassy state displays a broad heterogeneous distribution of rotational angles, about 80° in width, centered at a flip angle of 180°, which stays essentially constant over a wide temperature range. Thus, the phenylene motion that can consistently be observed in NMR and neutron scattering experiments is sensitive to the local packing.
Temperature dependence of high- and low-resistance bistable states in polycrystalline NiO films
Authors: Jung Kyooho , Seo Hongwoo , Kim Yongmin , Im Hyunsik , Hong JinPyo , Park Jae-Wan , Lee Jeon-Kook
Published: February 2007

The resistance switching current-voltage (I-V) characteristics in polycrystalline NiO films were investigated in the temperature range of 10K<T<300K. Very clear reversible resistive switching phenomena were observed in the entire temperature range. An analysis of the temperature dependence of the resistance switching transport revealed additional features, not reported in previous studies, that weak metallic conduction and correlated barrier polaron hopping coexist in the high-resistance off state and that relative dominance depends on the temperature and defect configuration. In addition, the authors propose that metallic Ni defects, existing near polycrystalline (or granular) boundaries, play a key role in the formation of a metallic channel.
Age under-estimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae?
Authors: Francis Malcolm P. , Campana Steven E. , Jones Cynthia M.
Published: February 2007

Annual deposition of growth bands in vertebrae has been validated for many shark species, and is now widely regarded as the norm. However, vertebrae are part of the shark’s axial skeleton, and band deposition may stop in old sharks when somatic growth ceases. We aged vertebral sections from New Zealand porbeagle sharks (Lamna nasus) under reflected white light and using X-radiographs. Bomb radiocarbon assays supported vertebral age estimates up to ~20 years, but not at older ages. The results suggest that older porbeagles were under-aged by as much as 50% from vertebral band counts, presumably because band width declined to a point where it became unresolvable. This has important implications for growth studies on other long-lived sharks. Estimated ages at sexual maturity were 8–11 years for males and 15–18 years for females, and longevity may be ~65 years. New Zealand and North Atlantic porbeagles differ in these parameters, and in length at maturity and maximum length, suggesting genetic isolation of the two populations.
Maturity and growth characteristics of a commercially exploited stingray, Dasyatis dipterura
Authors: Smith Wade D. , Cailliet Gregor M. , Melendez Everardo Mariano
Published: February 2007

Maturity and growth characteristics were estimated for Dasyatis dipterura from western Mexico, where it is a common component of artisanal elasmobranch fisheries. Median disc width at maturity was estimated as 57.3 cm for females (n = 126) and 46.5 cm for males (n = 55) respectively. Age estimates were obtained from 304 fishery-derived specimens (169 female, 135 male). An annual pattern of band-pair deposition was validated through modified centrum edge and marginal increment analyses. Gompertz, polynomial and von Bertalanffy growth models were fit to disc width and weight-at-age data. Resulting models were evaluated based on biological rationale, standard error of model estimates, and Akaike’s information criteria. Growth characteristics differed significantly between females and males. Maximum age estimates were 28 years for females and 19 years for males. Three-parameter von Bertalanffy growth models of disc width-at-age data generated the most appropriate fits and produced relatively low estimates of instantaneous growth rates for females (DW∞ = 92.4 cm, k = 0.05, t0 = –7.61, DW0 = 31.4 cm) and males (DW∞ = 62.2 cm, k = 0.10, t0 = –6.80, DW0 = 31.3 cm). These values are the lowest reported for myliobatiform stingrays and indicate slow growth rates in comparison with elasmobranchs in general.
Antioxidant defense response in a galling insect
Authors: Mittapalli Omprakash , Neal Jonathan J. , Shukle Richard H.
Published: February 2007

Herbivorous insect species are constantly challenged with reactive oxygen species (ROS) generated from endogenous and exogenous sources. ROS produced within insects because of stress and prooxidant allelochemicals produced by host plants in response to herbivory require a complex mode of antioxidant defense during insect/plant interactions. Some insect herbivores have a midgut-based defense against the suite of ROS encountered. Because the Hessian fly (
Mayetiola destructor
) is the major insect pest of wheat worldwide, and an emerging model for all gall midges, we investigated its antioxidant responses during interaction with its host plant. Quantitative data for two phospholipid glutathione peroxidases (
MdesPHGPX-1
and
MdesPHGPX-2
), two catalases (
MdesCAT-1
and
MdesCAT-2
), and two superoxide dismutases (
MdesSOD-1
and
MdesSOD-2
) revealed high levels of all of the mRNAs in the midgut of larvae on susceptible wheat (compatible interaction). During development of the Hessian fly on susceptible wheat, a differential expression pattern was observed for all six genes. Analysis of larvae on resistant wheat (incompatible interaction) compared with larvae on susceptible wheat showed increased levels of mRNAs in larvae on resistant wheat for all of the antioxidant genes except
MdesSOD-1
and
MdesSOD-2
. We postulate that the increased mRNA levels of
MdesPHGPX-1
,
MdesPHGPX-2
,
MdesCAT-1
, and
MdesCAT-2
reflect responses to ROS encountered by larvae while feeding on resistant wheat seedlings and/or ROS generated endogenously in larvae because of stress/starvation. These results provide an opportunity to understand the cooperative antioxidant defense responses in the Hessian fly/wheat interaction and may be applicable to other insect/plant interactions.
A gene cluster encoding cholesterol catabolism in a soil actinomycete provides insight into
Mycobacterium tuberculosis
survival in macrophages
Authors: Van der Geize Robert , Yam Katherine , Heuser Thomas , Wilbrink Maarten H. , Hara Hirofumi , Anderton Matthew C. , Sim Edith , Dijkhuizen Lubbert , Davies Julian E. , Mohn William W. , Eltis Lindsay D.
Published: February 2007

Rhodococcus
sp. strain RHA1, a soil bacterium related to
Mycobacterium tuberculosis
, degrades an exceptionally broad range of organic compounds. Transcriptomic analysis of cholesterol-grown RHA1 revealed a catabolic pathway predicted to proceed via 4-androstene-3,17-dione and 3,4-dihydroxy-9,10-seconandrost-1,3,5(10)-triene-9,17-dione (3,4-DHSA). Inactivation of each of the
hsaC
,
supAB
, and
mce4
genes in RHA1 substantiated their roles in cholesterol catabolism. Moreover, the
hsaC
−
mutant accumulated 3,4-DHSA, indicating that HsaC
RHA1
, formerly annotated as a biphenyl-degrading dioxygenase, catalyzes the oxygenolytic cleavage of steroid ring A. Bioinformatic analyses revealed that 51 rhodococcal genes specifically expressed during growth on cholesterol, including all predicted to specify the catabolism of rings A and B, are conserved within an 82-gene cluster in
M. tuberculosis
H37Rv and
Mycobacterium
bovis
bacillus Calmette–Guérin.
M. bovis
bacillus Calmette–Guérin grew on cholesterol, and
hsaC
and
kshA
were up-regulated under these conditions. Heterologously produced HsaC
H37Rv
and HsaD
H37Rv
transformed 3,4-DHSA and its ring-cleaved product, respectively, with apparent specificities ≈40-fold higher than for the corresponding biphenyl metabolites. Overall, we annotated 28 RHA1 genes and proposed physiological roles for a similar number of mycobacterial genes. During survival of
M. tuberculosis
in the macrophage, these genes are specifically expressed, and many appear to be essential. We have delineated a complete suite of genes necessary for microbial steroid degradation, and pathogenic mycobacteria have been shown to catabolize cholesterol. The results suggest that cholesterol metabolism is central to
M. tuberculosis
's unusual ability to survive in macrophages and provide insights into potential targets for novel therapeutics.
SUMO modification regulates inactivation of the voltage-gated potassium channel Kv1.5
Authors: Benson Mark D. , Li Qiu-Ju , Kieckhafer Katherine , Dudek David , Whorton Matthew R. , Sunahara Roger K. , Iñiguez-Lluhí Jorge A. , Martens Jeffrey R.
Published: February 2007

The voltage-gated potassium (Kv) channel Kv1.5 mediates the IKurrepolarizing current in human atrial myocytes and regulates vascular tone in multiple peripheral vascular beds. Understanding the complex regulation of Kv1.5 function is of substantial interest because it represents a promising pharmacological target for the treatment of atrial fibrillation and hypoxic pulmonary hypertension. Herein we demonstrate that posttranslational modification of Kv1.5 by small ubiquitin-like modifier (SUMO) proteins modulates Kv1.5 function. We have identified two membrane-proximal and highly conserved cytoplasmic sequences in Kv1.5 that conform to established SUMO modification sites in transcription factors. We find that Kv1.5 interacts specifically with the SUMO-conjugating enzyme Ubc9 and is a target for modification by SUMO-1, -2, and -3in vivo. In addition, purified recombinant Kv1.5 serves as a substrate in a minimalin vitroreconstituted SUMOylation reaction. The SUMO-specific proteases SENP2 and Ulp1 efficiently deconjugate SUMO from Kv1.5in vivoandin vitro, and disruption of the two identified target motifs results in a loss of the major SUMO-conjugated forms of Kv1.5. In whole-cell patch-clamp electrophysiological studies, loss of Kv1.5 SUMOylation, by either disruption of the conjugation sites or expression of the SUMO protease SENP2, leads to a selective ≈15-mV hyperpolarizing shift in the voltage dependence of steady-state inactivation. Reversible control of voltage-sensitive channels through SUMOylation constitutes a unique and likely widespread mechanism for adaptive tuning of the electrical excitability of cells.
The power of automated high-resolution behavior analysis revealed by its application to mouse models of Huntington's and prion diseases
Authors: Steele Andrew D. , Jackson Walker S. , King Oliver D. , Lindquist Susan
Published: February 2007

Automated analysis of mouse behavior will be vital for elucidating the genetic determinants of behavior, for comprehensive analysis of human disease models, and for assessing the efficacy of various therapeutic strategies and their unexpected side effects. We describe a video-based behavior-recognition technology to analyze home-cage behaviors and demonstrate its power by discovering previously unrecognized features of two already extensively characterized mouse models of neurodegenerative disease. The severe motor abnormalities in Huntington's disease mice manifested in our analysis by decreased hanging, jumping, stretching, and rearing. Surprisingly, behaviors such as resting and grooming were also affected. Unexpectedly, mice with infectious prion disease showed profound increases in activity at disease onset: rearing increased 2.5-fold, walking 10-fold and jumping 30-fold. Strikingly, distinct behaviors were altered specifically during day or night hours. We devised a systems approach for multiple-parameter phenotypic characterization and applied it to defining disease onset robustly and at early time points.
An editing-defective aminoacyl-tRNA synthetase is mutagenic in aging bacteria via the SOS response
Authors: Bacher Jamie M. , Schimmel Paul
Published: February 2007

Mistranslation in bacterial and mammalian cells leads to production of statistical proteins that are, in turn, associated with specific cell or animal pathologies, including death of bacterial cells, apoptosis of mammalian cells in culture, and neurodegeneration in the mouse. A major source of mistranslation comes from heritable defects in the editing activities of aminoacyl-tRNA synthetases. These activities clear errors of aminoacylation by deacylation of mischarged tRNAs. We hypothesized that, in addition to previously reported phenotypes in bacterial and mammalian systems, errors of aminoacylation could be mutagenic and lead to disease. As a first step in testing this hypothesis, the effect of an editing defect in a single tRNA synthetase on the accumulation of mutations in aging bacteria was investigated. A striking, statistically significant, enhancement of the mutation rate in aging bacteria was found. This enhancement comes from an increase in error-prone DNA repair through induction of the bacterial SOS response. Thus, mistranslation, as caused by an editing-defective tRNA synthetase, can lead to heritable genetic changes that could, in principle, be linked to disease.
Polo-like kinase 3 is required for entry into S phase
Authors: Zimmerman Wendy C. , Erikson Raymond L.
Published: February 2007

The polo-like kinase, Plk1, which is expressed and active in mitosis, is involved in regulation of mitotic entry, spindle pole assembly, mitotic exit, and cytokinesis [Donaldson MM, Tavares AA, Hagan IM, Nigg EA, Glover DM (2001)J Cell Sci114:2357–2358]. In mammals, there are two other members of the polo-like kinase family that are less well understood, Plk2 and Plk3.Plk3first was identified and cloned as an immediate early gene. Here, we report Plk3 localizes to the nucleolus and is involved in regulation of the G1/S phase transition. We demonstrate that the level of Plk3 protein is cell cycle regulated, peaking in G1. We have delivered Plk3-interfering RNA with lentivirus to serum-starved cells and found that, upon serum stimulation, Plk3 is required for cyclin E expression and entry into S phase. Plk3-interfering RNA-induced Plk3 depletion resulted in a large fraction of asynchronously proliferating cells to become quiescent. We propose the Plk3 requirement in the cell cycle is fulfilled in G1, and that once cells pass this point, they are able to complete cell division, whereas in the absence of Plk3, they fail to reenter the cell cycle. Additional data suggest that Plk3 may regulate entry into S phase in part through interaction with the phosphatase Cdc25A, because its depletion also resulted in attenuation of cyclin E expression.
Cardiac side population cells have a potential to migrate and differentiate into cardiomyocytes in vitro and in vivo
Authors: Oyama Tomomi , Nagai Toshio , Wada Hiroshi , Naito Atsuhiko Thomas , Matsuura Katsuhisa , Iwanaga Koji , Takahashi Toshinao , Goto Motohiro , Mikami Yoko , Yasuda Noritaka , Akazawa Hiroshi , Uezumi Akiyoshi , Takeda Shin'ichi , Komuro Issei
Published: February 2007

Side population (SP) cells, which can be identified by their ability to exclude Hoechst 33342 dye, are one of the candidates for somatic stem cells. Although bone marrow SP cells are known to be long-term repopulating hematopoietic stem cells, there is little information about the characteristics of cardiac SP cells (CSPs). When cultured CSPs from neonatal rat hearts were treated with oxytocin or trichostatin A, some CSPs expressed cardiac-specific genes and proteins and showed spontaneous beating. When green fluorescent protein–positive CSPs were intravenously infused into adult rats, many more (∼12-fold) CSPs were migrated and homed in injured heart than in normal heart. CSPs in injured heart differentiated into cardiomyocytes, endothelial cells, or smooth muscle cells (4.4%, 6.7%, and 29% of total CSP-derived cells, respectively). These results suggest that CSPs are intrinsic cardiac stem cells and involved in the regeneration of diseased hearts.
Type Iγ phosphatidylinositol phosphate kinase modulates adherens junction and E-cadherin trafficking via a direct interaction with μ1B adaptin
Authors: Ling Kun , Bairstow Shawn F. , Carbonara Chateen , Turbin Dmitry A. , Huntsman David G. , Anderson Richard A.
Published: February 2007

Assembly of E-cadherin–based adherens junctions (AJ) is obligatory for establishment of polarized epithelia and plays a key role in repressing the invasiveness of many carcinomas. Here we show that type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) directly binds to E-cadherin and modulates E-cadherin trafficking. PIPKIγ also interacts with the μ subunits of clathrin adaptor protein (AP) complexes and acts as a signalling scaffold that links AP complexes to E-cadherin. Depletion of PIPKIγ or disruption of PIPKIγ binding to either E-cadherin or AP complexes results in defects in E-cadherin transport and blocks AJ assembly. An E-cadherin germline mutation that loses PIPKIγ binding and shows disrupted basolateral membrane targeting no longer forms AJs and leads to hereditary gastric cancers. These combined results reveal a novel mechanism where PIPKIγ serves as both a scaffold, which links E-cadherin to AP complexes and the trafficking machinery, and a regulator of trafficking events via the spatial generation of phosphatidylinositol-4,5-bisphosphate.
Axons break in animals lacking β-spectrin
Authors: Hammarlund Marc , Jorgensen Erik M. , Bastiani Michael J.
Published: February 2007

Axons and dendrites can withstand acute mechanical strain despite their small diameter. In this study, we demonstrate that β-spectrin is required for the physical integrity of neuronal processes in the nematode Caenorhabditis elegans. Axons in β-spectrin mutants spontaneously break. Breakage is caused by acute strain generated by movement because breakage can be prevented by paralyzing the mutant animals. After breaking, the neuron attempts to regenerate by initiating a new growth cone; this second round of axon extension is error prone compared with initial outgrowth. Because spectrin is a major target of calpain proteolysis, it is possible that some neurodegenerative disorders may involve the cleavage of spectrin followed by the breakage of neural processes.
Voltage Sensor Movement and cAMP Binding Allosterically Regulate an Inherently Voltage-independent Closed−Open Transition in HCN Channels
Authors: Chen Shan , Wang Jing , Zhou Lei , George Meena S. , Siegelbaum Steven A.
Published: February 2007

The hyperpolarization-activated cyclic nucleotide-modulated cation (HCN) channels are regulated by both membrane voltage and the binding of cyclic nucleotides to a cytoplasmic, C-terminal cyclic nucleotide-binding domain (CNBD). Here we have addressed the mechanism of this dual regulation for HCN2 channels, which activate with slow kinetics that are strongly accelerated by cAMP, and HCN1 channels, which activate with rapid kinetics that are weakly enhanced by cAMP. Surprisingly, we find that the rate of opening of HCN2 approaches a maximal value with extreme hyperpolarization, indicating the presence of a voltage-independent kinetic step in the opening process that becomes rate limiting at very negative potentials. cAMP binding enhances the rate of this voltage-independent opening step. In contrast, the rate of opening of HCN1 is much greater than that of HCN2 and does not saturate with increasing hyperpolarization over the voltage range examined. Domain-swapping chimeras between HCN1 and HCN2 reveal that the S4–S6 transmembrane region largely determines the limiting rate in opening kinetics at negative voltages. Measurements of HCN2 tail current kinetics also reveal a voltage-independent closing step that becomes rate limiting at positive voltages; the rate of this closing step is decreased by cAMP. These results are consistent with a cyclic allosteric model in which a closed–open transition that is inherently voltage independent is subject to dual allosteric regulation by voltage sensor movement and cAMP binding. This mechanism accounts for several properties of HCN channel gating and has potentially important physiological implications.
On the coefficients of Hilbert quasipolynomials
Authors: Bruns Winfried , Ichim Bogdan
Published: February 2007

The Hilbert function of a module over a positively graded algebra is of quasi-polynomial type (Hilbert–Serre). We derive an upper bound for its grade, i.e. the index from which on its coefficients are constant. As an application, we give a purely algebraic proof of an old combinatorial result (due to Ehrhart, McMullen and Stanley).
Matrix adherence of endothelial cells attenuates immune reactivity: induction of hyporesponsiveness in allo‐ and xenogeneic models
Authors: Methe Heiko , Groothuis Adam , Sayegh Mohamed H. , Edelman Elazer R.
Published: February 2007

Endothelial integrity regulates vascular tone, luminal patency, and the immune reactivity to tissue grafts. Endothelial dysfunction is the first marker and site of disease initiation and severity. It has long been known that endothelial biochemical function is density dependent, and we have recently shown that endothelial immunobiology is anchorage dependent. Matrix‐embedded endothelial cells (EC) establish a controlled anchorage state and are not only immune protected but also induce a system immune protective state. We now define this aspect of vascular and immune biology in detail. The in vitro immune response of allogeneic splenocytes (proliferation, lytic activity, and cytokine expression) on exposure to aortic EC was significantly reduced if EC were embedded within three‐dimensional collagen matrices (3D‐EC;P< 0.005) to an even greater extent than EC that had reached confluence as monolayers on tissue culture plates (EC‐TCPS). Splenocyte reactivity was enhanced with repeated exposure to EC‐TCPS but minimally if preexposed to 3D‐EC (P<0.002). 3D‐EC induced significantly greater differentiation of splenocytes into CD4+CD25+Foxp3+ regulatory T cells than EC‐TCPS (P< 0.02). The reduced response to 3D‐EC and potential protective effect to subsequent exposure were confirmed in vivo. Repeated exposure of immune‐competent mice to injections of xenogeneic EC‐TCPS induced vigorous host immunity. In contrast, prior implantation of 3D‐EC induced hyporesponsiveness toward subsequent injection of EC‐TCPS with reduced humoral response, decreased lytic activity, and lower frequency of effector splenocytes (P< 0.001). EC interaction with its matrix determines phenotype, viability, and biosecretory potential. We now show that this microenvironmental interaction also influences endothelial‐mediated activation of allo‐ and xenogeneic immune cells. 3D matrix‐embedding limits the ability of EC to initiate adaptive immunity, and initial exposure to 3D‐EC confers hyporesponsiveness to subsequent exposure to immunogeneic EC. These effects transcended the traditional control that confluence imposes on EC and reflects perhaps even higher order control. Our findings might offer novel insights to endothelialmediated diseases and potential cell‐based therapies.—Methe, H., Groothuis, A., Sayegh, M. H., Edelman, E. R. Matrix adherence of endothelial cells attenuates immune reactivity: induction of hyporesponsiveness in allo‐ and xenogeneic models. FASEB J. 21, 1515–1526 (2007)
Biphenyl 2,3′,4,5′,6‐pentakisphosphate, a novel inositol polyphosphate surrogate, modulates Ca2+ responses in rat hepatocytes
Authors: Vandeput Fabrice , Combettes Laurent , Mills Stephen J. , Backers Katrien , Wohlkönig Alexandre , Parys Jan B. , De Smedt Humbert , Missiaen Ludwig , Dupont Geneviève , Potter Barry V. L. , Erneux Christophe
Published: February 2007

Benzene polyphosphates containing phosphate groups on one ring are Ins(1,4,5)P3 5‐phosphatase inhibitors when evaluated against type‐I Ins(1,4,5)P3 5‐phosphatase. A novel biphenyl derivative, biphenyl 2,3′,4,5′,6‐pentakisphosphate, with five phosphate groups on two rings was synthesized: It inhibited the activity of two inositol 5‐phosphatases: type I and SHIP2 with Ins(1,3,4,5)P4 as substrate. The inhibition was competitive with respect to the substrate. IC50 value measured in rat hepatocytes, which contains the native Ins(1,4,5)P3 5‐phosphatase, was in the micromolar range at 1.0 μM Ins(1,4,5)P3 as substrate. Biphenyl 2,3′,4,5′,6‐pentakisphosphate did not affect the activity of Ins(1,4,5)P3 3‐kinase A in the 5‐100 μM range. Surprisingly, experimental evidence supports an effect of biphenyl 2,3′,4,5′,6‐pentakisphosphate at the level of the Ins(1,4,5)P3 receptor. Finally, when injected into rat hepatocytes, the analog affected the frequency of Ca2+ oscillations in a positive or negative way depending on its concentration. At very high concentrations of the analog, Ca2+ oscillations were even suppressed. These data were interpreted as a dual effect of the biphenyl 2,3′,4,5′,6‐pentakisphosphate on cytosolic [Ca2+] increases: an activation effect through an increase in Ins(1,4,5)P3 level via Ins(1,4,5)P3 5‐phosphatase inhibition and an inhibitory effect, which was exerted directly on the Ins(1,4,5)P3 receptor. Thus, our data show for the first time that the frequency of Ca2+ oscillations in response to a Ca2+‐mobilizing agonist can be controlled by inhibitors of type‐I Ins(1,4,5)P3 5‐phosphatase.—Vandeput, F., Combettes, L., Mills, S. J., Backers, K., Wohlkönig, A., Parys, J. B., De Smedt, H., Missiaen, L., Dupont, G., Potter, B. V. L., Erneux, C. Biphenyl 2,3′,4,5′,6‐pentakisphosphate, a novel inositol polyphosphate surrogate, modulates Ca2+ responses in rat hepatocytes. FASEB J. 21, 1481–1491 (2007)
Assessing Perceived Health and Associated Health‐Promoting Behaviors: An Investigation of Methods Used to Assess Health Status
Authors: Becker Craig M. , Glascoff Marry A. , Mitchell Terri , Durham Thomas W. , Arnold William
Published: February 2007

Health assessments have been integral in the development of health behavior and policy recommendations. As the nation's health status improves, information about positive health is needed to continue development of appropriate behavior and policy recommendations. In this study, perceived health, health behaviors, health care usage, and how participants defined health were assessed. Using reported health‐promoting behaviors, respondents were grouped into high‐, middle‐, and low‐health groups. Analyses found statistically significant differences (p<.05) for all health behaviors reported and for life satisfaction. Each group's understanding of health also differed significantly. Results document the discriminating value and importance of positive health‐promoting behaviors beyond their traditional role in prevention. Recommendations for health professionals' use of positive health assessments are discussed.
Controlled Endurance Exercise Training and VO2max Changes in Older Adults: A Meta‐Analysis
Authors: Huang Guoyuan , Gibson Cheryl A. , Tran Zung V. , Osness Wayne H.
Published: February 2007

This meta‐analysis of controlled clinical trials quantifies the effect of aerobic exercise on VO2max(aerobic fitness) among sedentary older adults and examines the associations of such magnitude with variables of intervention. Forty‐one trials including 2102 older subjects (within‐group mean age of 60 years and older) were identified by searches of databases, hand searching, and cross‐referencing. Outcomes were homogeneous. The pooled standardized effect size by a fixed‐effect model showed a higher moderate effect (mean ± SEM) of 0.64±0.05; 95% confidence interval, 0.56–0.73; p<0.001, representing a net increase in VO2max (mean ± SEM) of 3.78±0.28 mL · kg−1· min−1 ; 95% confidence interval, 3.24–4.33; or a 16.3% improvement, compared with control groups. Greater improvement in Vo2max was associated with training length more than 20 weeks and training intensity of approximately 60% but less than 70% of VO2max. Endurance training improves aerobic fitness in older adults, thus providing protective benefits for cardiovascular aging and quality of later life.
Obesity—A Critical Issue in Preventive Cardiology: The Bogalusa Heart Study
Authors: Berenson Gerald S.
Published: February 2007

Obesity has become a major public health problem in the United States, with a marked upward trend occurring over the past three decades. It plays a critical role in the development of cardiovascular risk factors that mediate the evolution of asymptomatic cardiovascular disease. Longitudinal observations of children, adolescents, and young adults enrolled in the Bogalusa Heart Study show that obesity persists over time and is linked to the clustering of components of metabolic syndrome including hyperinsulinemia/ insulin resistance, dyslipidemia, and hypertension, thereby creating a long‐term burden of cardiovascular risk beginning in childhood. This burden is associated with subclinical and adverse structural and functional changes of the cardiovascular system in youth. Ultimately, these changes can result in morbidity from disease, as exemplified in the Framingham Heart Study. Obesity is governed by the interplay of both genetic and environmental factors. Unlike genetic factors, lifestyle behaviors are amenable to modification. Since obesity is so widespread and underlying cardiovascular disease is so prevalent, health education beginning in childhood is suggested as an approach to prevention.
The Measurement and Prevalence of Depression in Patients With Chronic Heart Failure
Authors: Johansson Peter , Dahlström Ulf , Broström Anders
Published: February 2007

Chronic heart failure is a common disease accompanied by poor mental health and depression. The diagnosis of depression is based on the presence of affective, cognitive, and somatic symptoms assessed by categoric or dimensional instruments. Depression is prominent and high rates are found with dimensional instruments in hospitalized heart failure patients. Categoric instruments seem to be more reliable but are more complex to use. Because of poor outcomes, attention should also be paid to subthreshold depression. In screening for such cases, dimensional instruments might be preferable because of the risk for underestimation by categoric instruments. Dimensional instruments might also be easier to implement in daily practice but, to reduce bias, cutoff scores might need refinement according to the clinical setting. Therefore, studies that evaluate different cutoff values are needed to find a critical level of burden from a depressive symptomatology on outcomes such as mortality, hospitalizations, and quality of life.
Are There Gender Differences Related to Symptoms of Acute Myocardial Infarction? A Norwegian Perspective
Authors: Løvlien Mona , Schei Berit , Gjengedal Eva
Published: February 2007

The purpose of this study was to compare symptom presentation and illness behavior among women and men with acute myocardial infarction and assess various aspects that influence prehospital delay. This is a cross‐sectional, retrospective study using selfreported questionnaires. The sample consisted of 82 women and men in Norway, up to 65 years of age, with first‐time acute myocardial infarction between March and October 1999. The findings demonstrated that the most commonly reported symptom in both genders was chest pain. More than 90% of women and men experienced chest pain, with no difference between the genders. More women than men had nausea as well as pain located in their arms, back, jaw, and throat. More men than women attributed their symptoms to be cardiac in origin. Experiencing pain in the shoulders, attributing symptoms to be noncardiac, consulting a family member, and contacting several medical practitioners increased prehospital delay. During the year before the event, women were more likely to experience fatigue than men. The conclusion of this study is that women experienced a greater diversity of symptoms than men. Acute symptoms, interpretation of symptoms, and illness behavior may influence prehospital delay.
Ways of Experiencing the Life Situation Among United States Patients With an Implantable Cardioverter‐Defibrillator: A Qualitative Study
Authors: Bolse Kärstin , Hamilton Glenys , Flanagan Jane , Caroll Diane L. , Fridlund Bengt
Published: February 2007

The purpose of this paper is to describe how a selected group of United States patients with an implantable cardioverter‐ defibrillator perceived their life situation. A qualitative design based on the phenomenographic approach was chosen to describe the patients' conceptions of their life situation. Fourteen patients—eight men and six women, aged 21–84—were strategically selected to obtain as broad a variation as possible. The descriptive categories to emerge from the analysis of the interviews were trust, adaptability, and empowerment. The category labeled trust describes how patients trusted in the organization around them. The category labeled adaptability describes how patients adapted to living with an implantable cardioverter‐defibrillator device. The category entitled empowerment describes how patients considered that they received support from family and friends as well as from health care professionals. This study suggests the need for a holistic intervention program comprising family, work, and leisure, focusing on patients' future life situation.
Heart Transplantation and Altered Drug Response, Part I: Heart Transplantation and Innervation
Authors: Boettger Rebecca , Lee Joyce , Rifkin Celia , Kayser Steven
Published: February 2007

This first in a two‐part series of articles will review heart transplantation and the changes in innervation that occur as a result of the surgical procedure. The second article will review how individual drug response is altered and will outline management guidelines for treatment of specific conditions.
Illness Representation of Patients With Systolic Heart Failure
Authors: Cherrington Candace C. , Lawson Thomas N. , Clark Karen B.
Published: February 2007

Studies have shown that individuals influence their health outcomes, both positively and negatively, through their illness representation. To date, no studies describe the illness representation of persons with systolic heart failure, a significant contributor of morbidity and mortality in older adults. The purpose of this study was to describe illness representation in heart failure. Twenty‐two subjects with New York Heart Association class II or III systolic heart failure were recruited at a university‐based heart failure clinic. Illness representation was measured using the revised Illness Perception Questionnaire. The means on each of the 9 subscales were found to be significantly different from the neutral point of 3. The results suggest that participants believed that their heart failure was a chronic, cyclic disease with serious consequences that they could control through treatment. In addition, participants believed that they understood their heart failure and did not have a negative affective response to their heart failure.