bluuebunny/crossref_metadata_2025 huggingface dataset:
An ultrasonic method for determination of acoustic impedance, time of flight, and attenuation of a thin linear-viscoelastic layer
Authors: Yao Gui-Jin , Cui Zhi-Wen , Song Ruo-Long , Wang Ke-Xie
Published: November 2007

A method for the determination of acoustic impedance, time of flight, and attenuation of an immersed thin linear-viscoelastic layer on a substrate of infinite extent is proposed as the transfer functions of the normally incident ultrasonic reflected signals are given. Utilizing the derived analytical expressions related to the measured data, three parameters can be determined without considering the acoustic impedance of the substrate and giving the initial guesses and the corresponding convergence zones. The measurement relations between the layer properties and the three parameters are theoretically derived. The method stability against the experimental noises is numerically investigated.
Enhanced neutron concentration in uranium thin film waveguides
Authors: Pogossian S. P.
Published: November 2007

The theoretical feasibility of the miniaturization of nuclear energy production is discussed. It is shown how the characteristics of 4% enriched uranium thin film waveguides can be optimized in order to allow neutron concentration at high densities. The guiding uranium thin film is sandwiched between two ferromagnetic media. Since the neutron refractive index in thin magnetic films is spin dependent, this permits control of the neutron number in the uranium film by means of external magnetic fields.
Phonon spectrum and specific heat of silicon nanowires
Authors: Zhang Y. , Cao J. X. , Xiao Y. , Yan X. H.
Published: November 2007

Based on lattice dynamics theory and molecular dynamics simulations, we have investigated the geometrical structures, phonon dispersion relations, and specific heat of silicon nanowires with Stillinger-Weber potential. It was shown that the original Stillinger-Weber potential can reproduce the well-established four acoustical branches. With the calculated spectra, we calculated specific heats of silicon nanowires. It is found that the specific heats of thin nanowires are much higher than those of bulk silicon. According to the partial density of states of surface atoms, the enhancement of specific heats of silicon nanowires can be attributed to the surface effect and phonon confinement effect.
Study on the noise of silicon capacitive resonant mass sensors in ambient atmosphere
Authors: Kim Sang-Jin , Ono Takahito , Esashi Masayoshi
Published: November 2007

This article reports on the resolution of mass detection by optical and capacitive methods in ambient atmosphere using very thin single-crystalline silicon microcantilevers. The detectable minimum mass by optical sensing increases slightly with decreasing cantilever size due to temperature fluctuation noise. Using capacitive detection, a detectable minimum mass of below 1×10−14 g can be obtained using cantilevers with resonance frequencies of 78–80 kHz. From an experimental comparison, we find that the detectable minimum mass by capacitive detection is slightly smaller than that obtained by optical detection using a cantilever with resonant frequency of 78 kHz. Using theoretical modeling and experimental results relevant to gas adsorption-desorption to the sensor surface, it is found that the adsorption-desorption noise by gases with infinitesimal partial pressure in the air surrounding a cantilever significantly influences the resonance frequency fluctuation of the cantilever in the high resonance frequency region.
Microstructure analysis of epitaxially grown self-assembled Ge islands on nanometer-scale patterned SiO2∕Si substrates by high-resolution transmission electron microscopy
Authors: Yoon Tae-Sik , Kim Hyun-Mi , Kim Ki-Bum , Ryu Du Yeol , Russell Thomas P. , Zhao Zuoming , Liu Jian , Xie Ya-Hong
Published: November 2007

The microstructure of epitaxially grown self-assembled Ge islands on patterned SiO2∕Si substrates was analyzed using high resolution transmission electron microscopy. The Ge islands were grown by molecular beam epitaxy on hexagonally ordered Si hole arrays with ∼25 nm diameter and ∼40 nm center-to-center distance, which are covered by 30 nm thick SiO2 mask layer patterned using self-assembled diblock copolymers. The Ge islands nucleate preferentially at the edge of overetched Si surface, and subsequently grow selectively on Si surface as opposed to SiO2 surface with increasing coverage. The lattice planes of some Ge islands are tilted from those of Si substrates. This is believed to be the reason for the observed misalignment of moiré fringes. The diameter of the Ge islands is identical to that of Si holes for large Ge coverage due to the selective growth behavior. These islands are found to have dislocations at the interface with the Si substrate. These results highlight the important microstructural issues and growth behavior of quantum dots on patterned substrates.
Fluxonic cellular automata
Authors: Milošević M. V. , Berdiyorov G. R. , Peeters F. M.
Published: November 2007

We propose a quantum cellular automata composed of nanostructured mesoscopic superconducting squares, where the logic states are defined by two trapped vortices in a 2×2 blind hole matrix. We present the functioning logic gate based on this fluxonic cellular automata, where the logic operations are verified through theoretical simulations within the Ginzburg-Landau formalism. The input signals are defined using the vortex interaction with current loops placed on top of the two diagonal blind holes of the input cell. The readout technology may be chosen from a large variety of modern vortex imaging methods, transport, and local density of states measurements.
Origin of incoherent magnetic switching behavior in CoCrPt–SiO2 perpendicular magnetic recording media
Authors: Jung H. S. , Kuo M. , Malhotra S. S. , Bertero G.
Published: November 2007

Magnetic switching behavior for CoCrPt–SiO2 single layer media with oxygen contents (OCs) from 4% to 10% and recording layer thickness (tmag) from 2to27nm is investigated. Significant incoherent switching, caused by domain wall motion, and large activation volume are observed at tmag⩽6nm regardless of OC, consistent with nonuniform microstructure with less grain isolation at tmag=4nm. These results support formation of a highly exchange-coupled thin magnetic layer on top of Ru interlayer, which can explain the large difference between angular dependence of Hcr predicted by the Stoner-Wohlfarth theory and the experimental values.
Enhancement-mode GaAs metal-oxide-semiconductor high-electron-mobility transistors with atomic layer deposited Al2O3 as gate dielectric
Authors: Lin H. C. , Yang T. , Sharifi H. , Kim S. K. , Xuan Y. , Shen T. , Mohammadi S. , Ye P. D.
Published: November 2007

Enhancement-mode GaAs metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with ex situ atomic-layer-deposited Al2O3 as gate dielectrics are studied. Maximum drain currents of 211 and 263mA∕mm are obtained for 1μm gate-length Al2O3 MOS-HEMTs with 3 and 6nm thick gate oxide, respectively. C-V characteristic shows negligible hysteresis and frequency dispersion. The gate leakage current density of the MOS-HEMTs is 3–5 orders of magnitude lower than the conventional HEMTs under similar bias conditions. The drain current on-off ratio of MOS-HEMTs is ∼3×103 with a subthreshold swing of 90mV/decade. A maximum cutoff frequency (fT) of 27.3GHz and maximum oscillation frequency (fmax) of 39.9GHz and an effective channel mobility of 4250cm2∕Vs are measured for the 1μm gate-length Al2O3 MOS-HEMT with 6nm gate oxide. Hooge’s constant measured by low frequency noise spectral density characterization is 3.7×10−5 for the same device.
Magnetic properties of Ni2+ clusters in NaY zeolite
Authors: Mukadam M. D. , Yusuf S. M. , Sasikala R.
Published: November 2007

We have investigated the magnetic properties of Ni2+ exchanged NaY zeolite by using a direct current magnetization technique. At T>5 K, the M vs H/T curves superimpose and these curves could be fitted well using a Langevin function with a log-normal distribution of moments. The mean spin-cluster moment has been found to be ∼3.3μB. The deviation from the superposition of the M vs H/T curves is observed at T<5 K indicating the building up of a spin-spin correlation between Ni clusters below 5 K. The zero-field-cooled and field-cooled magnetization curves show branching at low temperatures (T≤5 K) under low applied magnetic fields (H≤1 kOe) with a peak in the zero-field-cooled magnetization curves. A log-normal distribution of spin-freezing/blocking temperature has been observed with mean spin-freezing/blocking temperature ∼3.0 K. The peak temperature Tg decreases with increasing field and follows the de Almeida–Thouless (AT) line [1−Tg(H)/Tg(0)]∝H2/3. The extrapolation of the AT line gives the spin-freezing temperature Tg(0)≈3.29 K.
Substrate influence on the shape of domains in epitaxial PbTiO3 thin films
Authors: Venkatesan Sriram , Kooi B. J. , De Hosson J. T. M. , Vlooswijk A. H. G. , Noheda B.
Published: November 2007

Epitaxial PbTiO3 thin films were grown on SrTiO3(001) and DyScO3(110) substrates by pulsed laser deposition. We used high-resolution transmission electron microscopy to investigate the 90° domain structure in the films. They were found to have a predominant fraction of c domains along with a certain minor volume fraction of a domains that is clearly higher in case of the DyScO3 substrates. In PbTiO3 on SrTiO3 the a domains were found to have a wedge shape, whereas in PbTiO3 on SrRuO3∕DyScO3 they have a nearly uniform width. The presence of steps in the domain walls has been observed in the films on both substrates, but the steps are clearly more dominant in the case of SrTiO3 than of SrRuO3∕DyScO3 and are responsible for the observed wedge shape. The observed difference in the films induced by the two substrates is attributed to a higher stiffness of SrTiO3 than of SrRuO3∕DyScO3 as we corroborated with nanoindentation experiments.
Extreme value analysis of Fiji's wind records
Authors: Rattan S P , Sharma R N
Published: November 2007

A number of extreme value analysis techniques are utilised to predict basic design gust wind speeds for Fiji, which lies in a tropical cyclone prone region. The study shows that a number of modern methods tend to highly under-predict extreme wind speeds in regions of Fiji severely affected by tropical cyclones, although their skills improve in less severely affected regions. The reference for comparison was Dorman?s method, which has been previously used as a guidance for development of Region D wind speeds in the Australian wind loading code ? the AS1170.2-1989. In the case of Fiji, this study recommends the AS1170.2-1989 Region C provisions for Suva and the eastern coasts of the main island of Viti Levu only, and the AS1170.2-1989 Region D provisions elsewhere. This is significantly different to the provisions of the current National Building Code of Fiji (1990) which allow for the use of AS1170.2-1989 Region C provisions for all of Fiji. This difference is attributed to differences in the frequency and intensity of tropical cyclones visiting Fiji as compared with those for Australian Region C.
Miscibility study of solution cast blends of poly(lactic acid) and poly(vinyl butyral)
Authors: Khurma J R , Rohindra D R , Devi R
Published: November 2007

Poly(lactic acid) (PLA) was blended with poly(viny1 butyral) (PVB) through solution casting method using chloroform as the common solvent. The films obtained were characterized for miscibility using Differential Scanning Calorimetry (DSC), tensile testing and FTIR spectroscopy. The DSC results showed that the glass-transition temperature (Tg) of the PLA and PVB remained more or less constant with the composition of the blend. The existence of two Tg?s in the blends indicated that PLA and PVB were immiscible over the composition range investigated. percentage crystallinity ( cc ), of PLA phase remained constant with increasing PVB content in the blend. FTIR measurements showed that there was no appreciable change in the spectra with respect to blend composition, implying the immiscibility of the two polymers. Mechanical analysis showed that the tensile strength and elongation decreased on blending.
Comparison of performance of whitewood (Endospermum medullosum L. S. Smith) provenances and families in Vanuatu
Authors: Vutilolo I V N , Tyagi A P , Thomson L A J , Heads M
Published: November 2007

This study reports a comparison of performance of four year-old whitewood (Endospermum medullosum L S Smith) provenances and families trials established by the Department of Forestry of Vanuatu and the South Pacific Regional Programme In Forest Genetic Resources project (SPRIG). Trees in the different open-pollinated, half-sibling families had mean heights ranging from 7.1 m to 10.2 m, dbh from 13.5 cm to 17.8 cm, wood volume from 0.07 to 0.14 m3 and survival from 54% to 91%. Seedlot GD11 from Shark Bay East Santo showed the superior mean height of 10.2 m followed by seedlot MT29 from Maewo and MS47 from Malel Central East Santo with 9.6 m. The shortest trees were in families JT35 (Forari, Efate) with 7.1 m, MT33 (Maewo) and JT30 (Forari, Efate) with 7.5 m. Trees in seedlots MS44 from Malel Central East Santo and MS32 from Palon East Santo had the biggest diameter increase(mean dbh of 17.8 cm) followed by seedlot GD11 Shark Bay East Santo and MS2 from Sara East Santo with 17.5 cm and MS55 from South East Santo with 17.4 cm. Seedlots with very low diameter increment were MT3 from Maewo and JT35 from Forari (mean dbh of 13.5 cm) followed by MT3 and MT4 from Central Pentecost with a mean dbh of 13.8 cm. Seedlots with superior wood volume production were MS2 from Sara East Santo (with mean of 0.15 m3 per tree) followed by seedlots MS32 Palon East Santo, GD11 Shark Bay East Santo, MS55 South East Santo with 0.14 m3 and MS3 Kole East Santo with 0.13 m3. The slowest growing seedlots were JT35 from Forari Efate and MT32 from Maewo with mean volume of 0.07 m3. Study reveals that there is a great potential among provenances and families for further improvement and to establish breeding programme to breed whitewood for higher quantity and better timber quality.
Mapping the cloud-to-ground lightning occurrence in Fiji
Authors: Ramachandran V , Kishore A , Kumar S
Published: November 2007

Using the Time Of Group Arrival (TOGA) of sferics two year (Jan2003-Dec2004) annual average of about 3,200 and 1,200 cloud-to-ground (CG) flashes were recorded in the two larger islands, Viti Levu and Vanua Levu, Fiji. A two year average CG flash density showed maxima of 0.80 and 0.35 flashes/km2 per year in two islands. The diurnal variation showed peak activity between 14:00 hrs- 16:00 hrs LT and the seasonal variation showed enhanced lightning incidences during November-April. Data from Lightning Imaging Sensor (LIS) aboard the NASA Tropical Rainfall Measuring Mission (TRMM) satellite are also presented for the same period at the two locations. Lightning in a 10 km �10 km area was compared with total rain accumulation at a site midway in the area which shows good correlation.
Using perspectives on subject learning to inform the design of subject teaching: an example from science education
Authors: Ametller Jaume , Leach John , Scott Phil
Published: November 2007

The difficulty of using insights from educational research and scholarship to inform the design of subject teaching is widely acknowledged. In this article, we present an example of the design of a short science teaching intervention to illustrate one approach to using insights from research to inform the design of teaching. After outlining the general difficulty in question, the article begins by justifying two design tools in terms of perspectives on science learning (learning demand and communicative approach). We show how these design tools were used to generate a design brief for the teaching, and how the design brief was addressed through one worked example. We consider the role of factors other than educational research and scholarship in the design process. The article concludes with a discussion of this approach to designing teaching as compared to approaches used in the North American design literature, and the (non‐Anglophone) European didactics literature.
Preparing to teach with ICT: subject knowledge, Didaktik and improvisation
Authors: Loveless Avril
Published: November 2007

The article argues that preparing to be, in Shulman's words, ‘ready, willing and able’ to teach with ICT can be supported by an integrative framework of teacher professional knowledge which recognizes connections between subject domain knowledge, the didactic relation with information and communications technology (ICT), and an openness of mind in the moments of teaching, similar to improvisation. A study of teaching with ICT in an English primary school illustrates links between understandings of Didaktik and improvisation as teachers draw imaginatively upon subject knowledge to represent content and purpose appropriately for their pupils. The article discusses a relationship between understandings of Didaktik and improvisation, and the importance of conceptual subject domain knowledge in primary teacher education at a time of debate about curriculum, technology and professional knowledge.
Transforming domain knowledge: a systemic view at the school curriculum
Authors: Hameyer Uwe
Published: November 2007

What happens to domain knowledge on its way into the school curriculum?The article explores this question from a systems view of the knowledge transformation process. This process is not only bound tocontextual knowledgeaboutsocial forcesbut also to the school's owneducational knowledgeframework. Further, utilizing knowledge depends on images oflearningandlearnerswhich have a powerful impact on theenactedschool curriculum (instructional knowledge). The rationaleandmeaningfulness of a syllabus or a curriculum, of materials, media or textbooks also affect what is learned and taught (curriculum knowledge). In addition, our images of meaningful learning filter how domain knowledge is represented in the curriculum and put into practice. A conceptual framework is developed to understand the complexity of knowledge transformation with regard to learning purposes and recommendations for research.
Prodi's Narrow Victory and Italian Politics: One Year on
Authors: Newell James L.
Published: November 2007

The general election of April 2006 marked a further milestone, and possibly a turning point, in the recent trajectory of Italian politics. Unexpectedly narrow, the election outcome brought to government a coalition which, in the immediate aftermath of the campaign, appeared to face one of two possibilities: that either it would find the very precariousness of its position to be, paradoxically, its strength, giving it a degree of cohesion it might otherwise not have had, or that it would succumb to opposition attempts to exploit the divisions in its ranks and therefore fail to last for any length of time. Early indications pointed in both directions. In the second place, if the immediate consequence of the outcome appeared to be a strengthening of the position of Berlusconi (since he had been expected to lose by a wide margin and had instead apparently staged a dramatic comeback) then the 2006 defeat appeared to create the need for a redefinition of the Casa delle libertà, with a reduction in the role of Berlusconi himself and a new prime-ministerial candidate. Third, in bringing about the second alternation in government since the party-system upheavals of the early 1990s, the outcome appeared to represent the consolidation of a bi-polar party system based on fragmented coalitions. However, precisely because of the system's fragmentation and the seeming precariousness of the in-coming government's position, there appeared to be room for considerable doubt about the likely direction of future party-system developments. In short, if the election appeared to represent the confirmation of past trends, in other respects it looked as though it might also represent the start of a new period of uncertainty in Italian politics.
Mcl-1 determines the Bax dependency of Nbk/Bik-induced apoptosis
Authors: Gillissen Bernhard , Essmann Frank , Hemmati Philipp G. , Richter Antje , Richter Anja , Öztop Ilker , Chinnadurai Govindaswamy , Dörken Bernd , Daniel Peter T.
Published: November 2007

B cell lymphoma 2 (Bcl-2) homology domain 3 (BH3)–only proteins of the Bcl-2 family are important functional adaptors that link cell death signals to the activation of Bax and/or Bak. The BH3-only protein Nbk/Bik induces cell death via an entirely Bax-dependent/Bak-independent mechanism. In contrast, cell death induced by the short splice variant of Bcl-x depends on Bak but not Bax. This indicates that Bak is functional but fails to become activated by Nbk. Here, we show that binding of myeloid cell leukemia 1 (Mcl-1) to Bak persists after Nbk expression and inhibits Nbk-induced apoptosis in Bax-deficient cells. In contrast, the BH3-only protein Puma disrupts Mcl-1–Bak interaction and triggers cell death via both Bax and Bak. Targeted knockdown of Mcl-1 overcomes inhibition of Bak and allows for Bak activation by Nbk. Thus, Nbk is held in check by Mcl-1 that interferes with activation of Bak. The finding that different BH3-only proteins rely specifically on Bax, Bak, or both has important implications for the design of anticancer drugs targeting Bcl-2.
Mitosis persists in the absence of Cdk1 activity when proteolysis or protein phosphatase activity is suppressed
Authors: Skoufias Dimitrios A. , Indorato Rose-Laure , Lacroix Françoise , Panopoulos Andreas , Margolis Robert L.
Published: November 2007

Cellular transition to anaphase and mitotic exit has been linked to the loss of cyclin-dependent kinase 1 (Cdk1) kinase activity as a result of anaphase-promoting complex/cyclosome (APC/C)–dependent specific degradation of its cyclin B1 subunit. Cdk1 inhibition by roscovitine is known to induce premature mitotic exit, whereas inhibition of the APC/C-dependent degradation of cyclin B1 by MG132 induces mitotic arrest. In this study, we find that combining both drugs causes prolonged mitotic arrest in the absence of Cdk1 activity. Different Cdk1 and proteasome inhibitors produce similar results, indicating that the effect is not drug specific. We verify mitotic status by the retention of mitosis-specific markers and Cdk1 phosphorylation substrates, although cells can undergo late mitotic furrowing while still in mitosis. Overall, we conclude that continuous Cdk1 activity is not essential to maintain the mitotic state and that phosphatase activity directed at Cdk1 substrates is largely quiescent during mitosis. Furthermore, the degradation of a protein other than cyclin B1 is essential to activate a phosphatase that, in turn, enables mitotic exit.
The ATR-mediated S phase checkpoint prevents rereplication in mammalian cells when licensing control is disrupted
Authors: Liu Enbo , Lee Alan Yueh-Luen , Chiba Takuya , Olson Erin , Sun Peiqing , Wu Xiaohua
Published: November 2007

DNA replication in eukaryotic cells is tightly controlled by a licensing mechanism, ensuring that each origin fires once and only once per cell cycle. We demonstrate that the ataxia telangiectasia and Rad3 related (ATR)–mediated S phase checkpoint acts as a surveillance mechanism to prevent rereplication. Thus, disruption of licensing control will not induce significant rereplication in mammalian cells when the ATR checkpoint is intact. We also demonstrate that single-stranded DNA (ssDNA) is the initial signal that activates the checkpoint when licensing control is compromised in mammalian cells. We demonstrate that uncontrolled DNA unwinding by minichromosome maintenance proteins upon Cdt1 overexpression is an important mechanism that leads to ssDNA accumulation and checkpoint activation. Furthermore, we show that replication protein A 2 and retinoblastoma protein are both downstream targets for ATR that are important for the inhibition of DNA rereplication. We reveal the molecular mechanisms by which the ATR-mediated S phase checkpoint pathway prevents DNA rereplication and thus significantly improve our understanding of how rereplication is prevented in mammalian cells.
Peroxiredoxin 6 is required for blood vessel integrity in wounded skin
Authors: Kümin Angelika , Schäfer Matthias , Epp Nikolas , Bugnon Philippe , Born-Berclaz Christiane , Oxenius Annette , Klippel Anke , Bloch Wilhelm , Werner Sabine
Published: November 2007

Peroxiredoxin 6 (Prdx6) is a cytoprotective enzyme with largely unknown in vivo functions. Here, we use Prdx6 knockout mice to determine its role in UV protection and wound healing. UV-mediated keratinocyte apoptosis is enhanced in Prdx6-deficient mice. Upon skin injury, we observe a severe hemorrhage in the granulation tissue of knockout animals, which correlates with the extent of oxidative stress. At the ultrastructural level endothelial cells appear highly damaged, and their rate of apoptosis is enhanced. Knock-down of Prdx6 in cultured endothelial cells also increases their susceptibility to oxidative stress, thus confirming the sensitivity of this cell type to loss of Prdx6. Wound healing studies in bone marrow chimeric mice demonstrate that Prdx6-deficient inflammatory and endothelial cells contribute to the hemorrhage phenotype. These results provide insight into the cross-talk between hematopoietic and resident cells at the wound site and the role of reactive oxygen species in this interplay.
Nuclear fusion during yeast mating occurs by a three-step pathway
Authors: Melloy Patricia , Shen Shu , White Erin , McIntosh J. Richard , Rose Mark D.
Published: November 2007

In Saccharomyces cerevisiae, mating culminates in nuclear fusion to produce a diploid zygote. Two models for nuclear fusion have been proposed: a one-step model in which the outer and inner nuclear membranes and the spindle pole bodies (SPBs) fuse simultaneously and a three-step model in which the three events occur separately. To differentiate between these models, we used electron tomography and time-lapse light microscopy of early stage wild-type zygotes. We observe two distinct SPBs in ∼80% of zygotes that contain fused nuclei, whereas we only see fused or partially fused SPBs in zygotes in which the site of nuclear envelope (NE) fusion is already dilated. This demonstrates that SPB fusion occurs after NE fusion. Time-lapse microscopy of zygotes containing fluorescent protein tags that localize to either the NE lumen or the nucleoplasm demonstrates that outer membrane fusion precedes inner membrane fusion. We conclude that nuclear fusion occurs by a three-step pathway.
Site-1 protease is essential for endochondral bone formation in mice
Authors: Patra Debabrata , Xing Xiaoyun , Davies Sherri , Bryan Jennifer , Franz Carl , Hunziker Ernst B. , Sandell Linda J.
Published: November 2007

Site-1 protease (S1P) has an essential function in the conversion of latent, membrane-bound transcription factors to their free, active form. In mammals, abundant expression of S1P in chondrocytes suggests an involvement in chondrocyte function. To determine the requirement of S1P in cartilage and bone development, we have created cartilage-specific S1P knockout mice (S1Pcko). S1Pcko mice exhibit chondrodysplasia and a complete lack of endochondral ossification even though Runx2 expression, Indian hedgehog signaling, and osteoblastogenesis is intact. However, there is a substantial increase in chondrocyte apoptosis in the cartilage of S1Pcko mice. Extraction of type II collagen is substantially lower from S1Pcko cartilage. In S1Pcko mice, the collagen network is disorganized and collagen becomes entrapped in chondrocytes. Ultrastructural analysis reveals that the endoplasmic reticulum (ER) in S1Pcko chondrocytes is engorged and fragmented in a manner characteristic of severe ER stress. These data suggest that S1P activity is necessary for a specialized ER stress response required by chondrocytes for the genesis of normal cartilage and thus endochondral ossification.
Making sense of cilia and flagella
Authors: Sloboda Roger D. , Rosenbaum Joel L.
Published: November 2007

Data reported at an international meeting on the sensory and motile functions of cilia, including the primary cilium found on most cells in the human body, have thrust this organelle to the forefront of studies on the cell biology of human disease.
Climate change and the northern Russian treeline zone
Authors: MacDonald G.M , Kremenetski K.V , Beilman D.W
Published: November 2007

The Russian treeline is a dynamic ecotone typified by steep gradients in summer temperature and regionally variable gradients in albedo and heat flux. The location of the treeline is largely controlled by summer temperatures and growing season length. Temperatures have responded strongly to twentieth-century global warming and will display a magnified response to future warming. Dendroecological studies indicate enhanced conifer recruitment during the twentieth century. However, conifers have not yet recolonized many areas where trees were present during the Medieval Warm period (
ca
AD 800–1300) or the Holocene Thermal Maximum (HTM;
ca
10 000–3000 years ago). Reconstruction of tree distributions during the HTM suggests that the future position of the treeline due to global warming may approximate its former Holocene maximum position. An increased dominance of evergreen tree species in the northern Siberian forests may be an important difference between past and future conditions. Based on the slow rates of treeline expansion observed during the twentieth century, the presence of steep climatic gradients associated with the current Arctic coastline and the prevalence of organic soils, it is possible that rates of treeline expansion will be regionally variable and transient forest communities with species abundances different from today's may develop.
Climate and wildfires in the North American boreal forest
Authors: Macias Fauria Marc , Johnson E.A
Published: November 2007

The area burned in the North American boreal forest is controlled by the frequency of mid-tropospheric blocking highs that cause rapid fuel drying. Climate controls the area burned through changing the dynamics of large-scale teleconnection patterns (Pacific Decadal Oscillation/El Niño Southern Oscillation and Arctic Oscillation, PDO/ENSO and AO) that control the frequency of blocking highs over the continent at different time scales. Changes in these teleconnections may be caused by the current global warming. Thus, an increase in temperature alone need not be associated with an increase in area burned in the North American boreal forest. Since the end of the Little Ice Age, the climate has been unusually moist and variable: large fire years have occurred in unusual years, fire frequency has decreased and fire–climate relationships have occurred at interannual to decadal time scales. Prolonged and severe droughts were common in the past and were partly associated with changes in the PDO/ENSO system. Under these conditions, large fire years become common, fire frequency increases and fire–climate relationships occur at decadal to centennial time scales. A suggested return to the drier climate regimes of the past would imply major changes in the temporal dynamics of fire–climate relationships and in area burned, a reduction in the mean age of the forest, and changes in species composition of the North American boreal forest.
The effect of climate anomalies and human ignition factor on wildfires in Russian boreal forests
Authors: Achard Frédéric , Eva Hugh D , Mollicone Danilo , Beuchle René
Published: November 2007

Over the last few years anomalies in temperature and precipitation in northern Russia have been regarded as manifestations of climate change. During the same period exceptional forest fire seasons have been reported, prompting many authors to suggest that these in turn are due to climate change. In this paper, we examine the number and areal extent of forest fires across boreal Russia for the period 2002–2005 within two forest categories: ‘intact forests’ and ‘non-intact forests’. Results show a far lower density of fire events in intact forests (5–14 times less) and that those events tend to be in the first 10 km buffer zone inside intact forest areas. Results also show that, during exceptional climatic years (2002 and 2003), fire event density is twice that found during normal years (2004 and 2005) and average areal extent of fire events (burned area) in intact forests is 2.5 times larger than normal. These results suggest that a majority of the fire events in boreal Russia are of human origin and a maximum of one-third of their impact (areal extension) can be attributed to climate anomalies alone, the rest being due to the combined effect of human disturbances and climate anomalies.
Hierarchical path analysis of deer responses to direct and indirect effects of climate in northern forest
Authors: Mysterud Atle , Yoccoz Nigel G , Langvatn Rolf , Pettorelli Nathalie , Stenseth Nils Chr
Published: November 2007

A problem in climate studies has been on how to treat causal chains of explanations and both direct and indirect effects. Mammals in strongly seasonal environments of the boreal forest typically lose condition during winter and gain mass (and reproduce) during the summer season when biomass and plant quality peak. Mass decay of large herbivores during winter is due to direct effects of winter weather, such as increased costs of movement, thermoregulation and reduced access to food when snow is deep. Deer condition during summer is thought to be affected mainly indirectly by weather through plants. High spring temperature speeds up plant development, and deep snow can delay phenology in early summer. Current statistical modelling does not take into account these mechanistic pathways. We used hierarchical Bayes modelling to more mechanistically link global climate, local weather and plant phenology to autumn body mass of red deer in Norway. Red deer were much more affected indirectly through trophic interactions. No solid evidence of direct effects of snow depth was found on autumn body mass. We discuss the implications of our results relative to our ability to predict effects of global change on large mammalian herbivores in the boreal forest.
Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch
Authors: Post Eric , Forchhammer Mads C
Published: November 2007

In highly seasonal environments, offspring production by vertebrates is timed to coincide with the annual peak of resource availability. For herbivores, this resource peak is represented by the annual onset and progression of the plant growth season. As plant phenology advances in response to climatic warming, there is potential for development of a mismatch between the peak of resource demands by reproducing herbivores and the peak of resource availability. For migratory herbivores, such as caribou, development of a trophic mismatch is particularly likely because the timing of their seasonal migration to summer ranges, where calves are born, is cued by changes in day length, while onset of the plant-growing season on the same ranges is cued by local temperatures. Using data collected since 1993 on timing of calving by caribou and timing of plant growth in West Greenland, we document the consequences for reproductive success of a developing trophic mismatch between caribou and their forage plants. As mean spring temperatures at our study site have risen by more than 4°C, caribou have not kept pace with advancement of the plant-growing season on their calving range. As a consequence, offspring mortality has risen and offspring production has dropped fourfold.
Risk of fatal overdose during and after specialist drug treatment: the VEdeTTE study, a national multi‐site prospective cohort study
Authors: Davoli Marina , Bargagli Anna M. , Perucci Carlo A. , Schifano Patrizia , Belleudi Valeria , Hickman Matthew , Salamina Giuseppe , Diecidue Roberto , Vigna‐Taglianti Federica , Faggiano Fabrizio ,   for the VEdeTTE Study Group
Published: November 2007

Background  Specialist drug treatment is critical to overdose prevention; methadone maintenance is effective, but we lack evidence for other modalities. We evaluate the impact of a range of treatments for opiate dependence on overdose mortality.

Methods  Prospective cohort study of 10 454 heroin users entering treatment 1998–2001 in Italy followed‐up for 10 208 person‐years in treatment and 2914 person‐years out of treatment. Standardized overall mortality ratios (SMR) estimate excess mortality risk for heroin users in and out of treatment compared to the general population. Cox models compare the hazard ratio (HR) of overdose between heroin users in treatment and out of treatment.

Results  There were 41 overdose deaths, 10 during treatment and 31 out of treatment, generating annual mortality rates of 0.1% and 1.1% and SMRs of 3.9 [95% confidence interval (CI) 2.8–5.4] and 21.4 (16.7–27.4), respectively. Retention in any treatment was protective against overdose mortality (HR 0.09 95% CI 0.04–0.19) compared to the risk of mortality out of treatment, independent of treatment type and potential confounders. The risk of a fatal overdose was 2.3% in the month immediately after treatment and 0.77% in the subsequent period; compared to the risk of overdose during treatment the HR was 26.6 (95% CI 11.6–61.1) in the month immediately following treatment and 7.3 (3.3–16.2) in the subsequent period.

Conclusions  We demonstrate that a range of treatments for heroin dependence reduces overdose mortality risk. However, the considerable excess mortality risk in the month following treatment indicates the need for greater health education of drug users and implementation of relapse and overdose death prevention programmes. Further investigation is needed to measure and weigh the potential benefits and harms of short‐term therapies for opiate use.
A Quality Prediction Framework for Multistage Machining Processes Driven by an Engineering Model and Variation Propagation Model
Authors: Li Jianming , Freiheit Theodor , Jack Hu S. , Koren Yoram
Published: November 2007

This paper proposes a comprehensive quality prediction framework for multistage machining processes, connecting engineering design with the activities of quality modeling, variation propagation modeling and calculation, dimensional variation evaluation, dimensional variation analysis, and quality feedback. Presented is an integrated information model utilizing a hybrid (feature/point-based) dimensional accuracy and variation quality modeling approach that incorporates Monte Carlo simulation, variation propagation, and regression modeling algorithms. Two important variations (kinematic and static) for the workpiece, machine tool, fixture, and machining processes are considered. The objective of the framework is to support the development of a quality prediction and analysis software tool that is efficient in predicting part dimensional quality in a multistage machining system (serial, parallel, or hybrid) from station level to system level.
Drilling Characteristics of an E-Glass Fabric-Reinforced Polypropylene Composite and an Aluminum Alloy: A Comparative Study
Authors: Dandekar C. , Orady E. , Mallick P. K.
Published: November 2007

This paper presents an experimental study on the drilling characteristics of an E-glass fabric-reinforced polypropylene composite and aluminum alloy 6061-T6. Both materials have many similar structural applications, especially in the automotive industry. The drilling characteristics considered were axial thrust force, torque, temperature increase during drilling, and chip morphology. Both axial thrust force and torque were significantly higher for the aluminum alloy but were independent of the cutting speed for both materials. However, both increased linearly with increasing feed rate for the composite, but nonlinearly for the aluminum alloy. The Shaw-Oxford equation for predicting axial thrust and torque worked well with the aluminum alloy but did not fit the composite’s axial thrust and torque characteristics. Both materials exhibited temperature rise at locations close to the drilled hole. The temperature rise decreased with increasing feed rate as well as increasing cutting speed; however, the maximum temperature rise in the composite was significantly lower than that in the aluminum alloy. There was also a significant difference in the morphology of chips of these two materials.
Theoretical Analysis of the Coincident Wire-Powder Laser Deposition Process
Authors: Pinkerton Andrew J. , Syed Waheed Ul Haq , Li Lin
Published: November 2007

The process of coincident wire and powder deposition by laser has recently emerged in research work as a layered manufacturing method with a higher deposition rate than the established laser direct metal deposition technique and as a means of creating functionally graded metallic surface layers in a single pass. This work analytically models the process by accounting for the incoming wire and powder as virtual negative heat sources. The major assumptions of the model are confirmed experimentally and the predicted temperature profiles compared with values measured using contact and pyrometric methods. Model accuracy outside the molten zone is excellent, but this solution does not account for latent heat and intrapool circulation effects so it gives only moderate precision when extrapolated to within the melt pool. Increasing the mass feed rate to the melt pool reduces its depth and the temperature surrounding it—these effects can be quantified in three dimensions by the model.
Fluidized Bed Assisted Abrasive Jet Machining (FB-AJM): Precision
Internal Finishing of Inconel 718 Components
Authors: Barletta M. , Ceccarelli D. , Guarino S. , Tagliaferri V.
Published: November 2007

The relatively new technique of fluidized bed assisted abrasive jet machining (FB-AJM) is applied to finishing the inner surfaces of tubular Inconel 718 components. The effects of abrasive size, jet pressure, and machining cycle were evaluated, and the behavior of abrasive cutting edges acting against the surface during the process to remove material is accounted for. The finished surface was found to be highly dependent on jet pressure because it affects the abrasive contact against the surface as well as the finishing force acting on the abrasive, on the abrasive grain size, which controls the depth of cut, and on machining cycle, which controls the interaction time between the abrasives and the surface being finished. By altering these conditions, this process achieves surface roughness (Ra) as fine as 0.1μm and imparts minimal additional residual stress on the surface. This study also reveals the mechanisms that determine the smoothing of the inner surface of Inconel 718 tubes and improve the form accuracy, i.e., the internal roundness of the Inconel 718 tube.
Metal Transfer in Double-Electrode Gas Metal Arc Welding
Authors: Li Kehai , Zhang YuMing
Published: November 2007

Gas metal arc welding (GMAW) is the most widely used process for metal joining because of its high productivity and good quality, but analysis shows that the fundamental characteristic restricts conventional GMAW from further increasing the welding productivity. A novel GMAW process, refereed to as double-electrode GMAW or DE-GMAW, thus has been developed to make it possible to increase the melting current while the base metal current can still be controlled at a desired level. This fundamental change provides an effective method to allow manufacturers to use high melting currents to achieve high melting speed and low base metal heat input. A series of experiments have been conducted to uncover the basic characteristics of this novel process. Results obtained from analyses of high-speed image sequences and recorded current signals suggest that DE-GMAW can lower the critical current for achieving the desired spray transfer, shift the droplet trajectory, reduce the diameter of the droplet, and increase the speed and (generation) rate of the droplets.
Bridging Gaps in Laser Transmission Welding of Thermoplastics
Authors: Van de Ven James D. , Erdman Arthur G.
Published: November 2007

Gaps at part interfaces pose a major challenge for laser transmission welding (LTW) of thermoplastics due to the reliance on contact conduction between the absorptive and transmissive parts. In industrial applications, gaps between parts can occur for a variety of tolerance and process control reasons. Previous experimental and modeling work in LTW has focused on gap-free joints, with little attention to bridging a gap with thermal expansion of the absorbing material. A two-dimensional comprehensive numerical model simulated bridging gaps in LTW. Using the model, operating parameters were selected for welding across a 12.7μm gap and a 25.4μm gap by creating sufficient thermal strain to bridge the gap and form a weld. Using these operating parameters, PVC samples were welded in a T-joint geometry with a designed gap. The quality of the welds was assessed visually, by destructive force testing and by measuring the weld size to quantify the weld strength. All the experimental samples, for the two gap sizes, bridged the gap and formed welds. The average weld strength of the 12.7μm gap samples was 16.1MPa, while the 25.4μm gap samples had an average strength of 10.0MPa. Gaps were successfully bridged with LTW by using a two-dimensional model to design the operating parameters. To achieve higher modeling accuracy, a three-dimensional model might better simulate the thermal diffusion in the direction of laser travel.
yadBC
of
Yersinia pestis
, a New Virulence Determinant for Bubonic Plague
Authors: Forman Stanislav , Wulff Christine R. , Myers-Morales Tanya , Cowan Clarissa , Perry Robert D. , Straley Susan C.
Published: November 2007

In all
Yersinia pestis
strains examined, the adhesin/invasin
yadA
gene is a pseudogene, yet
Y. pestis
is invasive for epithelial cells. To identify potential surface proteins that are structurally and functionally similar to YadA, we searched the
Y. pestis
genome for open reading frames with homology to
yadA
and found three: the bicistronic operon
yadBC
(YPO1387 and YPO1388 of
Y. pestis
CO92; y2786 and y2785 of
Y. pestis
KIM5), which encodes two putative surface proteins, and YPO0902, which lacks a signal sequence and likely is nonfunctional. In this study we characterized
yadBC
regulation and tested the importance of this operon for
Y. pestis
adherence, invasion, and virulence. We found that loss of
yadBC
caused a modest loss of invasiveness for epithelioid cells and a large decrease in virulence for bubonic plague but not for pneumonic plague in mice.
Run reconstruction of mixed-stock salmon fisheries using age-composition data
Authors: Chasco Brandon , Hilborn Ray , Punt André E
Published: November 2007

A method for using age-composition data to determine stock-specific migration timing and abundance in a mixed-stock salmon fishery is developed. The Chignik sockeye salmon (Oncorhynchus nerka) fishery has two stocks, but only aggregate catch and escapement data are available. The age composition of the two stocks, however, is known to be consistently different, and age-composition data are collected from one stock at the beginning of the commercial fishing season and from the commercial catch throughout the season. Using the changes in age composition in the commercial catch throughout the season, we estimate the total abundance and migration timing for the two Chignik stocks using maximum likelihood and Bayesian methods. The outcomes of this stock separation model are highly correlated with that of scale pattern analysis for most years from 1978 to 2002 (r = 0.89). The results suggest that age composition may provide salmon managers with a reliable and inexpensive method for determining stock-specific migration timing and abundance in a mixed-stock fishery.