bluuebunny/crossref_metadata_2025 huggingface dataset:
Travelling wave magnetic resonance imaging at 3 T
Authors: Vazquez F. , Martin R. , Marrufo O. , Rodriguez A. O.
Published: August 2013

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore diameter limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies in magnetic resonance imaging and spectroscopy. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transverse electromagnetic modes and it can propagate any frequency. To study the potential benefits of travelling-wave excitation for whole-body imaging at 3 T, we compare numerical simulations of the principal mode propagation for a parallel-plate waveguide filled with a cylindrical phantom and two surface coils for all simulations at 1.5 T, 3 T, 4.7, 7 T, and 9.4 T. The principal mode shows very little variation of the field magnitude along the propagation direction at 3 T when compared to other higher resonant frequencies. Unlike the standard method for travelling-wave magnetic resonance imaging, a parallel-plate waveguide prototype was built and used together with a whole-body birdcage coil for signal transmission and a pair of circular coils for reception. Experimental B1 mapping was computed to investigate the feasibility of this approach and, the point spread function method was used to measure the imager performance. Human leg images were acquired to experimentally validate this approach. The numerical magnetic field and specific absorption rate of a simulated leg were computed and results are within the safety limits. The B1 mapping and point spread function results showed that it is possible to conduct travelling-wave imaging experiments with good imager performance. Human leg images were also obtained with the whole-body birdcage coil for comparison purposes. The simulated and in vivo travelling-wave results of the human leg correspond very well for the signal received. A similar image signal-to-noise ratio was observed for the travelling-wave approach and the conventional one. We have demonstrated the feasibility of travelling-wave magnetic resonance imaging at 3 T and whole-body magnetic resonance systems, using a parallel-plate waveguide with standard pulse sequences and only one coil array. This extends the use of the waveguide approach to a wider range of resonant frequencies.
Effect of low-frequency ultrasound on double-strand breaks in giant DNA molecules
Authors: Yoshida Kenji , Ogawa Naoki , Kagawa Yukihiro , Tabata Hiraku , Watanabe Yoshiaki , Kenmotsu Takahiro , Yoshikawa Yuko , Yoshikawa Kenichi
Published: August 2013

Double-strand breaks in giant DNA molecules caused by continuous ultrasound at a frequency of 30 kHz were quantified using single-molecule observations. The effect of the sound pressure was investigated by placing a tube containing DNA solution under an anti-node of the acoustic standing wave. Almost no breaks occurred below the threshold sound pressure. Above this threshold, the probability of strand breaks increased linearly with sound pressure. Acoustic cavitation detected with a hydrophone strongly suggests that the main mechanism of the DNA strand break is via cavitation generated by the ultrasound.
Collisional effects on nonlinear ion drag force for small grains
Authors: Hutchinson I. H. , Haakonsen C. B.
Published: August 2013

The ion drag force arising from plasma flow past an embedded spherical grain is calculated self-consistently and non-linearly using particle in cell codes, accounting for ion-neutral collisions. Using ion velocity distribution appropriate for ion drift driven by a force field gives wake potential and force greatly different from a shifted Maxwellian distribution, regardless of collisionality. The low-collisionality forces are shown to be consistent with estimates based upon cross-sections for scattering in a Yukawa (shielded) grain field, but only if non-linear shielding length is used. Finite collisionality initially enhances the drag force, but only by up to a factor of 2. Larger collisionality eventually reduces the drag force. In the collisional regime, the drift distribution gives larger drag than the shift distribution even at velocities where their collisionless drags are equal. Comprehensive practical analytic formulas for force that fit the calculations are provided.
The physical meaning of charge extraction by linearly increasing voltage transients from organic solar cells
Authors: Hanfland Robert , Fischer Martin A. , Brütting Wolfgang , Würfel Uli , MacKenzie Roderick C. I.
Published: August 2013

Carrier mobility in organic solar cells is almost exclusively determined with the Charge Extraction by Linearly Increasing Voltage (CELIV) technique; indeed much of our understanding of the recombination and charge transport mechanisms in organic solar cells is based on CELIV measurements. However, since the conception of the CELIV method, our understanding of organic semiconductors has significantly advanced. In this work, we critically examine the CELIV methods ability to provide accurate material data in the light of recent advances in our understanding of trap states and their influence on mobility in organic semiconductors. We then apply this knowledge to understand the mechanisms responsible for degradation in organic solar cells.
Micropower energy harvesting using poly(vinylidene fluoride hexafluoropropylene)
Authors: Sukwisute Pisan , Muensit Nantakan , Soontaranon Siriwat , Rugmai Supagorn
Published: August 2013

This work explores applications for poly(vinylidene fluoride hexafluoropropylene) or P(VDF-HFP). The P(VDF-HFP) with a 10 wt. % HFP can be prepared to exhibit the piezoelectricity and energy conversion ability. This was achieved by determining the nanostructural parameters by the Small Angle X-Ray Scattering. The unpoled sample gained linear crystallinity with drawing rate. The optimal conditions for poling process were 60 MV/m at 90 °C. The piezoelectric coefficient d31 of 28.7 pC/N and FoM of 8.8 × 10−12 m2/N were obtained from the poled sample drawn at 45 mm/min. The piezoelectric P(VDF-HFP) was proven to deliver a microwatt energy essential for powering small-scale electronics.
Improved conversion efficiency of GaN-based solar cells with Mn-doped absorption layer
Authors: Sheu Jinn-Kong , Huang Feng-Wen , Lee Chia-Hui , Lee Ming-Lun , Yeh Yu-Hsiang , Chen Po-Cheng , Lai Wei-Chih
Published: August 2013

GaN-based solar cells with Mn-doped absorption layer grown by metal-organic vapor-phase epitaxy were investigated. The transmittance spectrum and the spectral response showed the presence of an Mn-related band absorption property. Power-dependent, dual-light excitation, and lock-in amplifier techniques were performed to confirm if the two-photon absorption process occurred in the solar cells with Mn-doped GaN absorption layer. Although a slight decrease in an open circuit voltage was observed, a prominent increase in the short circuit current density resulted in a significant enhancement of the overall conversion efficiency. Under one-sun air mass 1.5 G standard testing condition, the conversion efficiency of Mn-doped solar cells can be enhanced by a magnitude of 5 times compared with the cells without Mn-doped absorption layer.
Sound insulation property of membrane-type acoustic metamaterials carrying different masses at adjacent cells
Authors: Zhang Yuguang , Wen Jihong , Zhao Honggang , Yu Dianlong , Cai Li , Wen Xisen
Published: August 2013

We present the experimental realization and theoretical understanding of membrane-type acoustic metamaterials embedded with different masses at adjacent cells, capable of increasing the transmission loss at low frequency. Owing to the reverse vibration of adjacent cells, Transmission loss (TL) peaks appear, and the magnitudes of the TL peaks exceed the predicted results of the composite wall. Compared with commonly used configuration, i.e., all cells carrying with identical mass, the nonuniformity of attaching masses causes another much low TL peak. Finite element analysis was employed to validate and provide insights into the TL behavior of the structure.
Ultra-compact optical modulator by graphene induced electro-refraction effect
Authors: Hao Ran , Du Wei , Chen Hongsheng , Jin Xiaofeng , Yang Longzhi , Li Erping
Published: August 2013

We report a highly tunable graphene embedded waveguide which overall modal index is in linear relationship with the in-plane permittivity of graphene and the electro-refraction effect has been significantly enhanced after graphene is embedded. An eight-layer graphene embedded Mach-Zender modulator has been theoretically demonstrated with the advantage of ultra-compact footprint (4 × 30 μm2), high modulation efficiency (20 V·μm), fast modulation speed, and large extinction ratio (35 dB). Our results may promote various on-chip active components, boosting the utilization of graphene in optical applications.
Modulating electronic transport properties of MoS2 field effect transistor by surface overlayers
Authors: Lin Jiadan , Zhong Jianqiang , Zhong Shu , Li Hai , Zhang Hua , Chen Wei
Published: August 2013

In situ bottom-gated molybdenum disulfide (MoS2) field effect transistors (FETs) device characterization and in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements were combined to investigate the effect of surface modification layers of C60 and molybdenum trioxide (MoO3) on the electronic properties of single layer MoS2. It is found that C60 decoration keeps MoS2 FET performance intact due to the very weak interfacial interactions, making C60 as an ideal capping layer for MoS2 devices. In contrast, decorating MoO3 on MoS2 induces significant charge transfer at the MoS2/MoO3 interface and largely depletes the electron charge carriers in MoS2 FET devices.
Gas loading of graphene-quartz surface acoustic wave devices
Authors: Whitehead E. F. , Chick E. M. , Bandhu L. , Lawton L. M. , Nash G. R.
Published: August 2013

Graphene was transferred to the propagation path of quartz surface acoustic wave devices and the attenuation due to gas loading of air and argon measured at 70 MHz and 210 MHz and compared to devices with no graphene. Under argon loading, there was no significant difference between the graphene and non-graphene device and the values of measured attenuation agree well with those calculated theoretically. Under air loading, at 210 MHz, there was a significant difference between the non-graphene and graphene devices, with the average value of attenuation obtained with the graphene devices being approximately twice that obtained from the bare quartz devices.
Liquid crystal phase shifters with a twist
Authors: Karwin C. M. , Livesey K. L.
Published: August 2013

The phase-shift per unit-length of microwave radiation passing through a liquid crystal cell is calculated. By using twisted nematics, as compared to the standard homogeneous nematic liquid crystal, the phase-shift per unit-length is increased over the transition region. This has the potential to lower the operating voltage and decrease the size of such phase shifters. In particular, the phase shifts for microwave radiation produced by the liquid crystals K15, E7, and E44 are calculated. It is found that liquid crystals with large values of the elastic constant ratio K22/K11 have their performance most improved when a twist is introduced.
Optimization of HfO2 films for high transconductance back gated graphene transistors
Authors: Lakshmi Ganapathi Kolla , Bhat Navakanta , Mohan Sangeneni
Published: August 2013

Hafnium dioxide (HfO2) films, deposited using electron beam evaporation, are optimized for high performance back-gated graphene transistors. Bilayer graphene is identified on HfO2/Si substrate using optical microscope and subsequently confirmed with Raman spectroscopy. Back-gated graphene transistor, with 32 nm thick HfO2 gate dielectric, has been fabricated with very high transconductance value of 60 μS. From the hysteresis of the current-voltage characteristics, we estimate the trap density in HfO2 to be in the mid 1011/cm2 range, comparable to SiO2.
Impacts of ambipolar carrier escape on current-voltage characteristics in a type-I quantum-well solar cell
Authors: Jo M. , Ding Y. , Noda T. , Mano T. , Sakuma Y. , Sakoda K. , Han L. , Sakaki H.
Published: August 2013

We study the current-voltage characteristics of a GaAs/AlGaAs quantum well solar cell (QWSC) at different temperatures. The photocurrent of the QWSC decreases from the short-circuit level with increasing forward bias, resulting in a low fill factor of the cell. The photocurrent reduction is attributed to the carrier confinement in the QW, which is investigated in detail by changing the temperature and excitation wavelength. We observe two reduction steps in the photocurrent at low temperature, and find that the different hole and electron tunneling rates are responsible for the two reductions.
Time-resolved measurement of pulse-to-pulse heating effects in a terahertz quantum cascade laser using an NbN superconducting detector
Authors: Valavanis A. , Dean P. , Scheuring A. , Salih M. , Stockhausen A. , Wuensch S. , Il'in K. , Chowdhury S. , Khanna S. P. , Siegel M. , Davies A. G. , Linfield E. H.
Published: August 2013

Joule heating causes significant degradation in the power emitted from terahertz-frequency quantum-cascade lasers (THz QCLs). However, to date, it has not been possible to characterize the thermal equilibration time of these devices, since THz power degradation over sub-millisecond time-scales cannot be resolved using conventional bolometric or pyroelectric detectors. In this letter, we use a superconducting antenna-coupled niobium nitride detector to measure the emission from a THz QCL with a nanosecond-scale time-resolution. The emitted THz power is shown to decay more rapidly at higher heat-sink temperatures, and in steady-state the power reduces as the repetition rate of the driving pulses increases. The pulse-to-pulse variation in active-region temperature is inferred by comparing the THz signals with those obtained from low duty-cycle measurements. A thermal resistance of 8.2 ± 0.6 K/W is determined, which is in good agreement with earlier measurements, and we calculate a 370 ± 90-μs bulk heat-storage time, which corresponds to the simulated heat capacity of the device substrate.
Deep ultraviolet photodiodes based on β-Ga2O3/SiC heterojunction
Authors: Nakagomi Shinji , Momo Toshihiro , Takahashi Syuhei , Kokubun Yoshihiro
Published: August 2013

A deep Ultraviolet (UV) photodiode was fabricated using a heterojunction between β-Ga2O3 with a band gap of 4.9 eV, and 6H-SiC with a band gap of 3.02 eV, and investigated its UV sensitivity. A thin β-Ga2O3 layer (200 nm) was prepared on a p-type 6H-SiC substrate through gallium evaporation in oxygen plasma. The device showed good rectifying properties. Under reverse bias, the current increased linearly with increasing deep-UV light intensity. The responsivity of the photodiode was highest to deep-UV light below a wavelength of 260 nm. The photodiode's response time to deep-UV light was in the order of milliseconds.
Multi-functional stacked light-trapping structure for stabilizing and boosting solar-electricity efficiency of hydrogenated amorphous silicon solar cells
Authors: Huang Wen-Hsien , Shieh Jia-Min , Pan Fu-Ming , Shen Chang-Hong , Huang Jung Y. , Wu Tsung-Ta , Kao Ming-Hsuan , Hsiao Tzu-Hsuan , Yu Peichen , Kuo Hao-Chung , Lee Ching-Ting
Published: August 2013

A sandwiched light-trapping electrode structure, which consists of a capping aluminum-doped ZnO (AZO) layer, dispersed plasmonic Au-nanoparticles (Au-NPs), and a micro-structured transparent conductive substrate, is employed to stabilize and boost the conversion-efficiency of hydrogenated amorphous silicon (a-Si:H) solar cells. The conformal AZO ultrathin layer (5 nm) smoothened the Au-NP-dispersed electrode surface, thereby reducing defects across the AZO/a-Si:H interface and resulting in a high resistance to photo-degradation in the ultraviolet-blue photoresponse band. With the plasmonic light-trapping structure, the cell has a high conversion-efficiency of 10.1% and the photo-degradation is as small as 7%.
Low voltage extrinsic switching of ferroelectric δ-PVDF ultra-thin films
Authors: Li Mengyuan , Katsouras Ilias , Asadi Kamal , Blom Paul W. M. , de Leeuw Dago M.
Published: August 2013

Non-volatile memories operating at low voltage are indispensable for flexible micro-electronic applications. To that end, ferroelectric δ-PVDF films were investigated as a function of layer thickness down to 10 nm ultra-thin films. Capacitors were fabricated using PEDOT:PSS as non-reactive electrode. Full polarization reversal was obtained at an unprecedented voltage below 5 V. The remanent polarization of 7 μC/cm2 and coercive field of 120 MV/m are independent of layer thickness, demonstrating that ferroelectric switching in δ-PVDF is extrinsic, dominated by inhomogeneous nucleation and growth. The ease of processing of δ-PVDF allowed to determine a lower limit of the critical ferroelectric thickness.
Variations of an Archetypal Scene: The Paris Métro Confrontation in Michael Haneke's Code Unknown
Authors: Andersson Johan
Published: August 2013

Michael Haneke's film Code Unknown (2000) depicts an interracial confrontation on the Paris Métro, which the critical literature has tended to discuss as a comment on European multiculturalism. In this paper I argue that this scene must also be understood as a variation of a string of similar interracial subway scenes that emerged in the New Hollywood era of American cinema in the late 1960s and 1970s. Reflecting interconnected changes in the American city and film industry, this subterranean scene constitutes a key example of a new form of graphically violent urban cinema. Haneke being an ardent critic of American entertainment violence, the appropriation of this scene in Code Unknown allows us to evaluate his counteraesthetic in ways that bridge thematic and auteurist approaches, and that take into account the crucial role of the spectator.
Dendrimer-Like Star-Branched Block Copolymers with Controlled Segment Sequence and their Star-Like Dendrigraft Derivatives
Authors: Zhang Chao , He Junpo
Published: August 2013

Star polymers with star-like arms, namely dendrimer-like star-branched block copolymers, were synthesised by anionic polymerisation with 1,3-bis(1-phenylethenyl)benzene (MDDPE) and divinylbenzene (DVB) as the coupling agents. The segment sequence was controlled by changing the polymerisation sequences of different monomers and coupling reactions. Two types of dendrimer-like star-branched block copolymers were prepared with polyisoprene (PI) block incorporated in the interior part or on the periphery. The PI chains in the resulting star copolymers were iteratively grafted through epoxidation and grafting reactions, forming star-like dendrigraft copolymers. The molecular conformation of the products in dilute solution was analysed by static and dynamic light scattering. These products adopt large sized globular conformation in dilute solution. Atomic force microscopy shows that the star-like dendrigraft copolymers appear as collapsed spheres on mica substrate.
Strengthening the impact of plant genetic resources through collaborative collection, conservation, characterisation, and evaluation: a tribute to the legacy of Dr Clive Francis
Authors: Berger Jens D. , Hughes Steve , Snowball Richard , Redden Bob , Bennett Sarita Jane , Clements Jon C. , Nawar Fawzy
Published: August 2013

This paper is a tribute to the legacy of Dr Clive Francis, who directly and indirectly collected >14 000 accessions across 60 genera of pasture, forage, and crop species and their wild relatives around the Mediterranean basin, Eastern Africa, and Central and South Asia from 1973 to 2005. This was achieved by a collaborative approach that built strong interactions between disparate organisations (ICARDA, VIR, CLIMA, and Australian genebanks) based on germplasm exchange, conservation and documentation, capacity building, and joint collection. These activities greatly strengthened Australian pasture, forage, and crop genebanks, and led to widespread germplasm utilisation that has waned in the last 5 years, reflecting changing priorities among industry funding bodies and research providers. This situation must be reversed, given the pivotal role genetic resource collections must play to broaden the genetic and adaptive base of plant breeding, to meet the challenge of feeding an increasing population in a depleting resource base. Because the use of germplasm subsets that facilitate phenotyping will stimulate wider utilisation of genetic resources, we discuss the application of core collection and germplasm selection through habitat characterisation/filtering in Australian collections. Both are valid entry points into large collections, but the latter has the advantage of enabling both trait discovery and investigation of plant adaptation, and because it is based on a priori hypothesis testing, it increases understanding even when the trait of interest is not identified.
Camelina (Camelina sativa (L.) Crantz): agronomic potential in Mediterranean environments and diversity for biofuel and food uses
Authors: Campbell M. C. , Rossi A. F. , Erskine W.
Published: August 2013

The oilseed camelina (Camelina sativa (L.) Crantz) was grown extensively in Northern Europe up to the 1950s. Increasing fuel prices coupled with a ‘diet-conscious’ society have revived interest in camelina for food and biofuel uses. This study assessed the agronomic potential of the crop under Mediterranean dryland conditions and the scope for selection in a diverse collection for food and biofuel use. Yield trials were conducted in the Western Australian wheatbelt between 1999 and 2008. In 14 environments, camelina gave an average yield of 1.04 t ha–1 compared with the canola (Brassica napus L.) control yield of 1.48 t ha–1. Camelina outyielded canola significantly at one site, whereas canola significantly outyielded camelina at five sites. Thirty accessions of camelina from five countries were compared in the field in 2011. Agronomic characteristics were recorded and fatty acid analyses performed; significant differences were observed. Accessions were identified with desirable biofuel qualities, and others selected as having fatty acid characteristics suitable for food use. Averaged over accessions, erucic acid content was high at 4.0%, ranging from 5.2% to a low of 2.5% in accession 4130. However, this line was tested in the agronomic trials and its fatty acid profiles varied greatly across environments. For stockfeed use, the protein content of the seed was found to be in range 23.2–29.1%.
Australian and Spanish scientists are collaborating in the domestication of tedera: young Merino sheep grazing a monoculture of tedera in autumn showed preference for certain accessions but no signs of ill health
Authors: Oldham C. , Real D. , Bailey H. J. , Thomas D. , Van Burgel A. , Vercoe P. , Correal E. , Rios S.
Published: August 2013

We hypothesised (i) that sheep grazing a monoculture of tedera (Bituminaria bituminosa (L.) C.H. Stirton var. albomarginata and var. crassiuscula) would not show signs of photosensitisation or ill health, and (ii) that when given free grazing choice they would show a repeatable preference for certain accessions of tedera related to their chemical composition. We tested this by grazing a group of young merino wethers on a monoculture containing seven accessions of tedera for 21 days. General health was assessed via daily visual checks for skin pinkness on the nose and ears, weekly measures of liveweight, condition score, and blood analysis compared with a group of control sheep fed wheaten hay ad libitum. The Chesson–Manly selection index was used to examine the relative preference of sheep for the seven accessions of tedera over the 21 days. Each accession of tedera was sampled weekly to estimate the dry matter on offer, and these samples were also analysed for crude protein, neutral detergent fibre, acid detergent fibre, in vitro digestibility, water soluble carbohydrates, minerals, and concentrations of the furanocoumarins psoralen and angelicin. None of the sheep showed any signs of ill health, with all blood parameters being within the normal reference range. All sheep gained weight and body condition over the 21 days. The difference in the rate of gain in condition score in favour of the sheep grazing tedera over the 21 days (0.014 v. 0.002 unit/sheep.day) was significant (P < 0.001). Sheep showed repeated preference for accessions T31 and T43 (α >0.143). Nutritive value of all accessions of tedera was high. However, only acid detergent fibre and neutral detergent fibre affected the relative preference of the sheep (P < 0.05) and they were only weakly correlated (r2 = 0.208 and 0.165, respectively). We conclude that there are accessions of tedera that are preferred by sheep that could be used to fill the autumn feed gap experienced in the south of Western Australia without any risk to the health of the sheep.
Effects of repeated fires on native plant community development at Hawaii Volcanoes National Park
Authors: Ainsworth Alison , Kauffman J. Boone
Published: August 2013

Catastrophic fires in wet forest have been highlighted as examples of drivers that overcome community resilience by altering feedback processes such that ecosystems are shifted into alternative, often less-desirable stable states. Recent successive lava-ignited wildfires, in slow-growing evergreen Myrtaceae-dominated mesic and wet forests at Hawaii Volcanoes National Park, provided an ideal opportunity to examine how forest species’ responses differ after single and repeated fires. In mesic (Metrosideros polymorpha–Dicranopteris linearis) and wet (Metrosideros–Cibotium glaucum) forests, the first fire was stand-replacing where 99% of the dominant overstorey trees (M. polymorpha) were top-killed; however, nearly half of these individuals survived by basal sprouting. The second fire dramatically increased mortality by killing the basal sprouts. Similarly, native tree fern C. glaucum survival was significantly reduced after repeated fires in the wet forest. The composition of the understorey in both communities after repeated fires differed in unexpected ways from once-burned and unburned forests. Repeated fires resulted in lower tree survival and rapid occupation by aggressive herbaceous species, potentially limiting tree growth and recruitment. The expected consequence is that native forest recovery will be delayed or even prevented by feedback processes established post-fire serving to maintain novel treeless alternate states.
Gap between science and media revisited: Scientists as public communicators
Authors: Peters Hans Peter
Published: August 2013

The present article presents an up-to-date account of the current media relations of scientists, based on a comprehensive analysis of relevant surveys. The evidence suggests that most scientists consider visibility in the media important and responding to journalists a professional duty—an attitude that is reinforced by universities and other science organizations. Scientific communities continue to regulate media contacts with their members by certain norms that compete with the motivating and regulating influences of public information departments. Most scientists assume a two-arena model with a gap between the arenas of internal scientific and public communication. They want to meet the public in the public arena, not in the arena of internal scientific communication. Despite obvious changes in science and in the media system, the orientations of scientists toward the media, as well as the patterns of interaction with journalists, have their roots in the early 1980s. Although there is more influence on public communication from the science organizations and more emphasis on strategic considerations today, the available data do not indicate abrupt changes in communication practices or in the relevant beliefs and attitudes of scientists in the past 30 y. Changes in the science–media interface may be expected from the ongoing structural transformation of the public communication system. However, as yet, there is little evidence of an erosion of the dominant orientation toward the public and public communication within the younger generation of scientists.
Communicating science in social settings
Authors: Scheufele Dietram A.
Published: August 2013

This essay examines the societal dynamics surrounding modern science. It first discusses a number of challenges facing any effort to communicate science in social environments: lay publics with varying levels of preparedness for fully understanding new scientific breakthroughs; the deterioration of traditional media infrastructures; and an increasingly complex set of emerging technologies that are surrounded by a host of ethical, legal, and social considerations. Based on this overview, I discuss four areas in which empirical social science helps clarify intuitive but sometimes faulty assumptions about the social-level mechanisms of science communication and outline an agenda for bench and social scientists—driven by current social-scientific research in the field of science communication—to guide more effective communication efforts at the societal level in the future.
Mechanistic patient-specific predictive correlation of tumor drug response with microenvironment and perfusion measurements
Authors: Pascal Jennifer , Bearer Elaine L. , Wang Zhihui , Koay Eugene J. , Curley Steven A. , Cristini Vittorio
Published: August 2013

Physical properties of the microenvironment influence penetration of drugs into tumors. Here, we develop a mathematical model to predict the outcome of chemotherapy based on the physical laws of diffusion. The most important parameters in the model are the volume fraction occupied by tumor blood vessels and their average diameter. Drug delivery to cells, and kill thereof, are mediated by these microenvironmental properties and affected by the diffusion penetration distance after extravasation. To calculate parameter values we fit the model to histopathology measurements of the fraction of tumor killed after chemotherapy in human patients with colorectal cancer metastatic to liver (coefficient of determination
R
2
= 0.94). To validate the model in a different tumor type, we input patient-specific model parameter values from glioblastoma; the model successfully predicts extent of tumor kill after chemotherapy (
R
2
= 0.7–0.91). Toward prospective clinical translation, we calculate blood volume fraction parameter values from in vivo contrast-enhanced computed tomography imaging from a separate cohort of patients with colorectal cancer metastatic to liver, and demonstrate accurate model predictions of individual patient responses (average relative error = 15%). Here, patient-specific data from either in vivo imaging or histopathology drives output of the model’s formulas. Values obtained from standard clinical diagnostic measurements for each individual are entered into the model, producing accurate predictions of tumor kill after chemotherapy. Clinical translation will enable the rational design of individualized treatment strategies such as amount, frequency, and delivery platform of drug and the need for ancillary non–drug-based treatment.
Attenuation of the posttranslational oscillator via transcription–translation feedback enhances circadian-phase shifts in
Synechococcus
Authors: Hosokawa Norimune , Kushige Hiroko , Iwasaki Hideo
Published: August 2013

Circadian rhythms are endogenous biological timing processes that are ubiquitous in organisms ranging from cyanobacteria to humans. In the photoautotrophic unicellular cyanobacterium
Synechococcus elongatus
PCC 7942, under continuous light (LL) conditions, the transcription–translation feedback loop (TTFL) of KaiC generates a rhythmic change in the accumulation of KaiC relative to KaiA clock proteins (KaiC/KaiA ratio), which peak and trough at subjective dawn and dusk, respectively. However, the role of TTFL in the cyanobacterial circadian system remains unclear because it is not an essential requirement for the basic oscillation driven by the Kai-based posttranslational oscillator (PTO) and the transcriptional output mechanisms. Here, we show that TTFL is important for the circadian photic resetting property in
Synechococcus
. The robustness of PTO, which is exemplified by the amplitude of the KaiC phosphorylation cycle, changed depending on the KaiC/KaiA ratio, which was cyclic under LL. After cells were transferred from LL to the dark, the clock protein levels remained constant in the dark. When cells were transferred from LL to continuous dark at subjective dawn, the KaiC phosphorylation cycle was attenuated with a lower KaiC/KaiA ratio, a higher KaiC phosphorylation level, and a lower amplitude than that in cells transferred at subjective dusk. We also found that the greater the degree to which PTO was attenuated in continuous dark, the greater the phase shifts upon the subsequent light exposure. Based on these results, we propose that TTFL enhances resetting of the Kai-based PTO in
Synechococcus
.
Neandertals made the first specialized bone tools in Europe
Authors: Soressi Marie , McPherron Shannon P. , Lenoir Michel , Dogandžić Tamara , Goldberg Paul , Jacobs Zenobia , Maigrot Yolaine , Martisius Naomi L. , Miller Christopher E. , Rendu William , Richards Michael , Skinner Matthew M. , Steele Teresa E. , Talamo Sahra , Texier Jean-Pierre
Published: August 2013

Modern humans replaced Neandertals ∼40,000 y ago. Close to the time of replacement, Neandertals show behaviors similar to those of the modern humans arriving into Europe, including the use of specialized bone tools, body ornaments, and small blades. It is highly debated whether these modern behaviors developed before or as a result of contact with modern humans. Here we report the identification of a type of specialized bone tool,
lissoir
, previously only associated with modern humans. The microwear preserved on one of these
lissoir
is consistent with the use of
lissoir
in modern times to obtain supple, lustrous, and more impermeable hides. These tools are from a Neandertal context proceeding the replacement period and are the oldest specialized bone tools in Europe. As such, they are either a demonstration of independent invention by Neandertals or an indication that modern humans started influencing European Neandertals much earlier than previously believed. Because these finds clearly predate the oldest known age for the use of similar objects in Europe by anatomically modern humans, they could also be evidence for cultural diffusion from Neandertals to modern humans.
Cytoplasmic streaming in plant cells emerges naturally by microfilament self-organization
Authors: Woodhouse Francis G. , Goldstein Raymond E.
Published: August 2013

Many cells exhibit large-scale active circulation of their entire fluid contents, a process termed cytoplasmic streaming. This phenomenon is particularly prevalent in plant cells, often presenting strikingly regimented flow patterns. The driving mechanism in such cells is known: myosin-coated organelles entrain cytoplasm as they process along actin filament bundles fixed at the periphery. Still unknown, however, is the developmental process that constructs the well-ordered actin configurations required for coherent cell-scale flow. Previous experimental works on streaming regeneration in cells of Characean algae, whose longitudinal flow is perhaps the most regimented of all, hint at an autonomous process of microfilament self-organization driving the formation of streaming patterns during morphogenesis. Working from first principles, we propose a robust model of streaming emergence that combines motor dynamics with both microscopic and macroscopic hydrodynamics to explain how several independent processes, each ineffectual on its own, can reinforce to ultimately develop the patterns of streaming observed in the Characeae and other streaming species.
Language can boost otherwise unseen objects into visual awareness
Authors: Lupyan Gary , Ward Emily J.
Published: August 2013

Linguistic labels (e.g., “chair”) seem to activate visual properties of the objects to which they refer. Here we investigated whether language-based activation of visual representations can affect the ability to simply detect the presence of an object. We used continuous flash suppression to suppress visual awareness of familiar objects while they were continuously presented to one eye. Participants made simple detection decisions, indicating whether they saw any image. Hearing a verbal label before the simple detection task changed performance relative to an uninformative cue baseline. Valid labels improved performance relative to no-label baseline trials. Invalid labels decreased performance. Labels affected both sensitivity (
d
′) and response times. In addition, we found that the effectiveness of labels varied predictably as a function of the match between the shape of the stimulus and the shape denoted by the label. Together, the findings suggest that facilitated detection of invisible objects due to language occurs at a perceptual rather than semantic locus. We hypothesize that when information associated with verbal labels matches stimulus-driven activity, language can provide a boost to perception, propelling an otherwise invisible image into awareness.
WNK1
-related Familial Hyperkalemic Hypertension results from an increased expression of L-WNK1 specifically in the distal nephron
Authors: Vidal-Petiot Emmanuelle , Elvira-Matelot Emilie , Mutig Kerim , Soukaseum Christelle , Baudrie Véronique , Wu Shengnan , Cheval Lydie , Huc Elizabeth , Cambillau Michèle , Bachmann Sebastian , Doucet Alain , Jeunemaitre Xavier , Hadchouel Juliette
Published: August 2013

Significance

Hypertension, one of the most common morbidity factors worldwide, is caused mostly by a deregulation of salt transport by the kidney, but underlying mechanisms remain elusive. The serine-threonine kinase With No lysine (K) 1 (WNK1) has been identified as a regulator of ion transport in the distal nephron, because its mutations cause Familial Hyperkalemic Hypertension (FHHt), a rare form of human hypertension. We generated a mouse model of WNK1-FHHt that fully recapitulates the disease and studied changes in expression of the Na
+
and K
+
transporters and channels involved in the maintenance of a correct blood pressure. Our study provides insights into the mechanisms underlying the pathogenesis of WNK1-FHHt and further corroborates the importance of WNK1 in ion homeostasis and blood pressure.
Tandem oleosin genes in a cluster acquired in Brassicaceae created tapetosomes and conferred additive benefit of pollen vigor
Authors: Huang Chien Yu , Chen Pei-Ying , Huang Ming-Der , Tsou Chih-Hua , Jane Wann-Neng , Huang Anthony H. C.
Published: August 2013

During evolution, genomes expanded via whole-genome, segmental, tandem, and individual-gene duplications, and the emerged redundant paralogs would be eliminated or retained owing to selective neutrality or adaptive benefit and further functional divergence. Here we show that tandem paralogs can contribute adaptive quantitative benefit and thus have been retained in a lineage-specific manner. In Brassicaceae, a tandem oleosin gene cluster of five to nine paralogs encodes ample tapetum-specific oleosins located in abundant organelles called tapetosomes in flower anthers. Tapetosomes coordinate the storage of lipids and flavonoids and their transport to the adjacent maturing pollen as the coat to serve various functions. Transfer-DNA and siRNA mutants of
Arabidopsis thaliana
with knockout and knockdown of different tandem oleosin paralogs had quantitative and correlated loss of organized structures of the tapetosomes, pollen-coat materials, and pollen tolerance to dehydration. Complementation with the knockout paralog restored the losses. Cleomaceae is the family closest to Brassicaceae.
Cleome
species did not contain the tandem oleosin gene cluster, tapetum oleosin transcripts, tapetosomes, or pollen tolerant to dehydration.
Cleome hassleriana
transformed with an
Arabidopsis
oleosin gene for tapetum expression possessed primitive tapetosomes and pollen tolerant to dehydration. We propose that during early evolution of Brassicaceae, a duplicate oleosin gene mutated from expression in seed to the tapetum. The tapetum oleosin generated primitive tapetosomes that organized stored lipids and flavonoids for their effective transfer to the pollen surface for greater pollen vitality. The resulting adaptive benefit led to retention of tandem-duplicated oleosin genes for production of more oleosin and modern tapetosomes.
Caspase-dependent regulation of the ubiquitin–proteasome system through direct substrate targeting
Authors: Yeh Ting-Chun , Bratton Shawn B.
Published: August 2013

Drosophilainhibitor of apoptosis (IAP) 1 (DIAP1) is an E3 ubiquitin ligase that regulates apoptosis in flies, in large part through direct inhibition and/or ubiquitinylation of caspases. IAP antagonists, such as Reaper, Hid, and Grim, are thought to induce cell death by displacing active caspases from baculovirus IAP repeat domains in DIAP1, but can themselves become targets of DIAP1-mediated ubiquitinylation. Herein, we demonstrate that Grim self-associates in cells and is ubiquitinylated by DIAP1 at Lys136 in an UbcD1-dependent manner, resulting in its rapid turnover. K48-linked ubiquitin chains are added almost exclusively to BIR2-bound Grim as a result of its structural proximity to DIAP1’s RING domain. However, active caspases can simultaneously cleave Grim at Asp132, removing the lysine necessary for ubiquitinylation as well as any existing ubiquitin conjugates. Cleavage therefore enhances the stability of Grim and initiates a feed-forward caspase amplification loop, resulting in greater cell death. In summary, Grim is a caspase substrate whose cleavage promotes apoptosis by limiting, in a target-specific fashion, its ubiquitinylation and turnover by the proteasome.
Direct atomic structure determination by the inspection of structural phase
Authors: Nakashima Philip N. H. , Moodie Alexander F. , Etheridge Joanne
Published: August 2013

A century has passed since Bragg solved the first atomic structure using diffraction. As with this first structure, all atomic structures to date have been deduced from the measurement of many diffracted intensities using iterative and statistical methods. We show that centrosymmetric atomic structures can be determined without the need to measure or even record a diffracted intensity. Instead, atomic structures can be determined directly and quickly from the observation of crystallographic phases in electron diffraction patterns. Furthermore, only a few phases are required to achieve high resolution. This represents a paradigm shift in structure determination methods, which we demonstrate with the moderately complex α-Al2O3. We show that the observation of just nine phases enables the location of all atoms with a resolution of better than 0.1 Å. This level of certainty previously required the measurement of thousands of diffracted intensities.
Dirigent domain-containing protein is part of the machinery required for formation of the lignin-based Casparian strip in the root
Authors: Hosmani Prashant S. , Kamiya Takehiro , Danku John , Naseer Sadaf , Geldner Niko , Guerinot Mary Lou , Salt David E.
Published: August 2013

Significance

The endodermis acts as a “second skin” in plant roots by providing the cellular control necessary for the selective entry of water and mineral nutrients into the vascular system. To enable such control, Casparian strips span the cell wall of adjacent endodermal cells to form a tight junction that blocks diffusion across the endodermis in the cell wall. This junction is composed of a fine band of lignin, the polymer that gives wood its strength. Here, we characterize a dirigent protein (from Latin,
dirigere
: to guide or align) as playing a vital role in the patterning of lignin in the Casparian strip, identifying a new component of the molecular machinery that builds Casparian strips.
Structures of human folate receptors reveal biological trafficking states and diversity in folate and antifolate recognition
Authors: Wibowo Ardian S. , Singh Mirage , Reeder Kristen M. , Carter Joshua J. , Kovach Alexander R. , Meng Wuyi , Ratnam Manohar , Zhang Faming , Dann Charles E.
Published: August 2013

Antifolates, folate analogs that inhibit vitamin B
9
(folic acid)-using cellular enzymes, have been used over several decades for the treatment of cancer and inflammatory diseases. Cellular uptake of the antifolates in clinical use occurs primarily via widely expressed facilitative membrane transporters. More recently, human folate receptors (FRs), high affinity receptors that transport folate via endocytosis, have been proposed as targets for the specific delivery of new classes of antifolates or folate conjugates to tumors or sites of inflammation. The development of specific, FR-targeted antifolates would be accelerated if additional biophysical data, particularly structural models of the receptors, were available. Here we describe six distinct crystallographic models that provide insight into biological trafficking of FRs and distinct binding modes of folate and antifolates to these receptors. From comparison of the structures, we delineate discrete structural conformations representative of key stages in the endocytic trafficking of FRs and propose models for pH-dependent conformational changes. Additionally, we describe the molecular details of human FR in complex with three clinically prevalent antifolates, pemetrexed (also Alimta), aminopterin, and methotrexate. On the whole, our data form the basis for rapid design and implementation of unique, FR-targeted, folate-based drugs for the treatment of cancer and inflammatory diseases.
Differential splicing across immune system lineages
Authors: Ergun Ayla , Doran Graeme , Costello James C. , Paik Henry H. , Collins James J. , Mathis Diane , Benoist Christophe ,   ImmGen Consortium, Blair David A. , Dustin Michael L. , Shinton Susan A. , Hardy Richard R. , Shay Tal , Regevc Aviv , Cohen Nadia , Brennan Patrick , Brenner Michael , Kim Francis , Nageswara Rao Tata , Wagers Amy , Heng Tracy , Ericson Jeffrey , Rothamel Katherine , Ortiz-Lopez Adriana , Mathis Diane , Benoist Christophe , Kreslavsky Taras , Fletcher Anne , Elpek Kutlu , Bellemare-Pelletier Angelique , Malhotra Deepali , Turley Shannon , Miller Jennifer , Brown Brian , Merad Miriam , Gautier Emmanuel L. , Jakubzick Claudia , Randolph Gwendalyn J. , Monach Paul , Best Adam J. , Knell Jamie , Goldrath Ananda , Jojic Vladimir , Koller Daphne , Laidlaw David , Collins Jim , Gazit Roi , Rossi Derrick J. , Malhotra Nidhi , Sylvia Katelyn , Kang Joonsoo , Bezman Natalie A. , Sun Joseph C. , Min-Oo Gundula , Kim Charlie C. , Lanier Lewis L.
Published: August 2013

Alternative splicing (AS) allows increased diversity and orthogonal regulation of the transcriptional products of mammalian genomes. To assess the distribution and variation of alternative splicing across cell lineages of the immune system, we comprehensively analyzed RNA sequencing and microarray data generated by the Immunological Genome Project Consortium. AS is pervasive: 60% of genes showed frequent AS isoforms in T or B lymphocytes, with 7,599 previously unreported isoforms. Distinct cell specificity was observed, with differential exon skipping in 5% of genes otherwise coexpressed in both B and T cells. The distribution of isoforms was mostly all or none, suggesting on/off switching as a frequent mode of AS regulation in lymphocytes. From the identification of differential exon use in the microarray data, clustering of exon inclusion/exclusion patterns across all Immunological Genome Project cell types showed that ∼70% of AS exons are distributed along a common pattern linked to lineage differentiation and cell cycling. Other AS events distinguished myeloid from lymphoid cells or affected only a small set of exons without clear lineage specificity (e.g.,
Ptprc
). Computational analysis predicted specific associations between AS exons and splicing regulators, which were verified by detection of the hnRPLL/
Ptprc
connection.