To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Understanding the properties of time averaging (age mixing) in a stratigraphic layer is essential for properly interpreting the paleofauna preserved in the geologic record. This work assesses the age and quantifies the scale and structure of time averaging of land snail-rich colluvial sediments from the Madeira Archipelago (Portugal) by dating individual shells using amino acid racemization calibrated with graphite-target and carbonate-target accelerator mass spectrometry radiocarbon methods. Gastropod shells of Actinella nitidiuscula were collected from seven sites on the volcanic islands of Bugio and Deserta Grande (Desertas Islands), where snail shells are abundant and well preserved in Quaternary colluvial deposits. Results show that the shells ranged in age from modern to ~48 cal ka BP (calibrated radiocarbon age), covering the last glacial and present interglacial periods. Snail shells retrieved from two of the colluvial sites exhibit multimillennial age mixing (>6 ka), which significantly exceeds the analytical error from dating methods and calibration. The observed multimillennial mixing of these assemblages should be taking into consideration in upcoming paleoenvironmental and paleoecological studies in the region. The extent of age mixing may also inform about the time span of colluvial deposition, which can be useful in future geomorphological studies. In addition, this study presents the first carbonate-target radiocarbon results for land snail shells and suggests that this novel, rapid, and more affordable dating method offers reliable age estimates for small land snail shells younger than ~20 cal ka BP.
We characterize the
knots in the 3-sphere and lens spaces that admit non-trivial L-space surgeries. As a corollary, 1-bridge braids in these manifolds admit non-trivial L-space surgeries. We also recover a characterization of the Berge manifold among 1-bridge braid exteriors.
We study the chromatic number of the curve graph of a surface. We show that the chromatic number grows like
for the graph of separating curves on a surface of Euler characteristic
. We also show that the graph of curves that represent a fixed nonzero homology class is uniquely
denotes its clique number. Together, these results lead to the best known bounds on the chromatic number of the curve graph. We also study variations for arc graphs and obtain exact results for surfaces of low complexity. Our investigation leads to connections with Kneser graphs, the Johnson homomorphism, and hyperbolic geometry.
The development of algorithms for agile science and autonomous exploration has been pursued in contexts ranging from spacecraft to planetary rovers to unmanned aerial vehicles to autonomous underwater vehicles. In situations where time, mission resources and communications are limited and the future state of the operating environment is unknown, the capability of a vehicle to dynamically respond to changing circumstances without human guidance can substantially improve science return. Such capabilities are difficult to achieve in practice, however, because they require intelligent reasoning to utilize limited resources in an inherently uncertain environment. Here we discuss the development, characterization and field performance of two algorithms for autonomously collecting water samples on VALKYRIE (Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer), a glacier-penetrating cryobot deployed to the Matanuska Glacier, Alaska (Mission Control location: 61°42′09.3″N 147°37′23.2″W). We show performance on par with human performance across a wide range of mission morphologies using simulated mission data, and demonstrate the effectiveness of the algorithms at autonomously collecting samples with high relative cell concentration during field operation. The development of such algorithms will help enable autonomous science operations in environments where constant real-time human supervision is impractical, such as penetration of ice sheets on Earth and high-priority planetary science targets like Europa.
Addition of wavelength selective absorbers on microbolometers tends to increase their thermal mass and slow their infrared response times. Making the bolometric material an integral part of the absorber and minimizing layer thicknesses is one possible way to maintain high detector speeds. Here, we study experimentally the effect on permittivity of adding a layer of semiconducting VOx between two layers of SiO2. Additionally, we investigate theoretically the effect on resonance wavelength of thinning the metal in metal-insulator-metal plasmonic resonant absorbers.
Liquid cell transmission electron microscopy (LCTEM) provides a unique insight into the dynamics of nanomaterials in solution. Controlling the addition of multiple solutions to the liquid cell remains a key hurdle in our ability to increase throughput and to study processes dependent on solution mixing including chemical reactions. Here, we report that a piezo dispensing technique allows for mixing of multiple solutions directly within the viewing area. This technique permits deposition of 50 pL droplets of various aqueous solutions onto the liquid cell window, before assembly of the cell in a fully controlled manner. This proof-of-concept study highlights the great potential of picoliter dispensing in combination with LCTEM for observing nanoparticle mixing in the solution phase and the creation of chemical gradients.
Recent surveys of multiple types of cancer reveal that most tumors are composed of populations of different cells with distinct sets of mutations. The variety of such subclones are thought to fuel drug resistance – targeting any single gene or pathway nearly always selects for those sub-clones lucky enough to have evolved backup mechanisms. The picture for treating cancer is thus becoming more clear: treating one cancer means keeping an entire population of cells in check. One angle, based on the principles of combinatorics that has worked in treating HIV for example, is to target multiple pathways simultaneously to better the chances of eliminating every malignant cell in the population. However, this approach requires gene regulatory network models that accurately describe the causes underlying tumor cell fitness.
This chapter overviews computational representations of genetic pathways for capturing salient aspects of tumor biology such as the activation of key genes and processes, how mutations confer gain- or loss-of-function in their cognate genes, and whether explanatory subnetworks can be identified for specific subtypes of disease. Pathway modeling provides a much-needed theoretical foundation to postulate tumor vulnerabilities that can scale to the consideration of multiple targets. Advances in the development of such mathematical frameworks should aid the clinical application of patient-specific treatments that minimize or eliminate malignant cell populations.
Cancer genomics utilizes a wide variety of data types on individual tumors. Microarrays have been used to profile genome copy number, gene expression, DNA methylation, and more. Profiling of DNA mutations, DNA breakpoints, gene fusions, RNA expression, and RNA editing are now becoming routine. These techniques have established that even though cancer is a genomically driven disease, any one type of genomic alteration is not enough to explain the altered be haviors and transcriptional states of various tumors. Drivers genes cluster into groups of biochemically interacting genes, and individual tumors often have a mutation in just one of the genes in the cluster. For example, PIK3CA or its suppressor PTEN is mutated in tumor samples far more frequently than expected, but samples with both mutations are far less frequent than expected. A full understanding of the diversity and pattern of mutations and abnormal regulation in cancer therefore requires integration of data types and the cellular network.
The present study investigated the relationship between the milk protein content of a rehydration solution and fluid balance after exercise-induced dehydration. On three occasions, eight healthy males were dehydrated to an identical degree of body mass loss (BML, approximately 1·8 %) by intermittent cycling in the heat, rehydrating with 150 % of their BML over 1 h with either a 60 g/l carbohydrate solution (C), a 40 g/l carbohydrate, 20 g/l milk protein solution (CP20) or a 20 g/l carbohydrate, 40 g/l milk protein solution (CP40). Urine samples were collected pre-exercise, post-exercise, post-rehydration and for a further 4 h. Subjects produced less urine after ingesting the CP20 or CP40 drink compared with the C drink (P< 0·01), and at the end of the study, more of the CP20 (59 (sd 12) %) and CP40 (64 (sd 6) %) drinks had been retained compared with the C drink (46 (sd 9) %) (P< 0·01). At the end of the study, whole-body net fluid balance was more negative for trial C ( − 470 (sd 154) ml) compared with both trials CP20 ( − 181 (sd 280) ml) and CP40 ( − 107 (sd 126) ml) (P< 0·01). At 2 and 3 h after drink ingestion, urine osmolality was greater for trials CP20 and CP40 compared with trial C (P< 0·05). The present study further demonstrates that after exercise-induced dehydration, a carbohydrate–milk protein solution is better retained than a carbohydrate solution. The results also suggest that high concentrations of milk protein are not more beneficial in terms of fluid retention than low concentrations of milk protein following exercise-induced dehydration.
This paper describes how space and place have been understood in gerontology as phenomenon that are both physical and social in character, yet are relatively bounded and static. The argument is posed as to how, following recent developments in human geography, a relational approach might be adopted. Involving a twist in current thinking, this would instead understand space and place each as highly permeable, fluid and networked at multiple scales. Moreover, it is proposed that the concept of ‘affect’ might also be insightful, recognising space and place as being relationally configured and performed, possessing a somatically registered energy, intensity and momentum that precedes deep cognition. Three vignettes illustrate the relationalities and affects in the lives and circumstances of older people, and how focusing more explicitly on them would allow for a richer understanding of where and how they live their lives. The paper closes with some thoughts on future theoretical, methodological and disciplinary considerations.
We have successfully developed a Seebeck coefficient Standard Reference Material (SRM™), Bi2Te3, that is essential for interlaboratory data comparison and for instrument calibration. Certification measurements were performed using a differential steady-state technique on 10 samples (15 measurements) randomly selected from a batch of 390 bars. The certified Seebeck coefficient values are provided from 10 to 390 K, and they are further supported by transient measurements. The availability of this SRM will validate measurement results, leading to a better understanding of the structure/property relationships and underlying physics of potential high-efficiency thermoelectric materials.
The influence of incorporating nanoparticulate additions into Ca3Co4O9 (CCO) thin films prepared by pulsed laser deposition using composite targets of CCO and CCO + 3wt% BaZrO3 (BZO) on Si and LaAlO3 substrates is investigated. X-ray data and high-resolution scanning electron microscopy reveal preferred c-axis orientation of the films deposited on Si substrates with the formation of nanoparticles between ∼ 10 – 50 nm. Preliminary thermoelectric behavior shows an enhancement of the power factor α2/ρ at room temperature. The microstructure and thermoelectric behavior of the CCO films are compared to the BZO-doped films.
We present Keck/HIRES spectra of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices, and a Magellan/MIKE spectrum of a star in the classical dwarf spheroidal galaxy (dSph) Sculptor. Our data include the first high-resolution spectroscopic observations of extremely metal-poor stars ([Fe/H] < −3.0) not belonging to the Milky Way (MW) stellar halo field population. We obtain abundance measurements and upper limits for up to 26 elements between carbon and europium. The stars span a range of −3.8 < [Fe/H] < −2.3, with the ultra-faints having large spreads in Fe. A comparison with MW halo stars of similar metallicity reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and Sculptor and the MW halo for the light, α and iron-peak elements (C to Zn). This agreement contrasts with the results of earlier studies of more metal-rich stars (−2.5 ≲[Fe/H]≲ −1.0) in more luminous dwarfs, which found significant abundance discrepancies with respect to the MW halo data. The abundances of neutron-capture elements (Sr to Eu) in all three galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]≳ −3.0. Our results are broadly consistent with a galaxy formation model which predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]≳ −2.5) of the MW inner halo, but we propose that dwarf galaxies similar to the dSphs are the primary contributors to the metal-poor end of the metallicity distribution of the MW outer halo.
Recent research in whole-plant stomatal physiology, conducted largely with potted plants in controlled
environments, suggests that stomatal conductance (gs) might be more closely linked to plant chemical variables
than to hydraulic variables. To test this in a field situation, seasonal gs was examined in relation to a number of
plant and environmental variables in 11 temperate, deciduous forest tree species. Stomatal conductance was
generally better correlated with environmental variables (air temperature, vapor pressure deficit, PPFD) than with
plant variables, and slightly better correlated with plant hydraulic variables (shoot water and osmotic potentials)
than with plant chemical variables (xylem sap ABA concentration, xylem sap pH). We examined a model,
developed previously for maize, which describes regulation of gs by xylem sap ABA concentration with leaf water
status acting to modify stomatal sensitivity to the ABA signal. This model explained slightly more variation in
seasonal gs in the forest trees than did single plant variables but not more variation than most single environmental
variables. Response surface models, especially those incorporating environmental variables, were more consistently
successful at explaining gs across species.
The results of architectural recording within the North Range of the University's Old Schools are described. Argued to have stood independently as a hall in the later fourteenth century, the progressive development of the Schools' quadrangle, and extensive alterations to it – culminating in Wright's neo-classical facade of 1754–58 – reflects upon the historical development of academic architecture. The prestigious display of the complex in the mid eighteenth century, facilitated through the mass levelling of domestic properties, equally tells of the institutional ‘realization’ of the University.
Email your librarian or administrator to recommend adding this to your organisation's collection.