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We study the number of random permutations needed to invariably generate the symmetric group Sn when the distribution of cycle counts has the strong α-logarithmic property. The canonical example is the Ewens sampling formula, for which the special case α = 1 corresponds to uniformly random permutations.
For strong α-logarithmic measures and almost every α, we show that precisely ⌈(1−αlog2)−1⌉ permutations are needed to invariably generate Sn with asymptotically positive probability. A corollary is that for many other probability measures on Sn no fixed number of permutations will invariably generate Sn with positive probability. Along the way we generalize classic theorems of Erdős, Tehran, Pyber, Łuczak and Bovey to permutations obtained from the Ewens sampling formula.
Between 2003 and 2007, North Gasherbrum Glacier on the northeastern slope of the Karakoram mountains in Asia underwent a dramatic acceleration, during which a velocity wave propagated down the glacier. There was a significant transfer of ice from up-glacier downstream, which resulted in a strong surface elevation increase over the lower tongue, but only a moderate advance of the glacier snout. We interpret this behaviour as that of a glacier surge, and we explain the observations by means of a simple version of the Kamb drainage-switching theory.
The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism Met allele exacerbates amyloid (Aβ) related decline in episodic memory (EM) and hippocampal volume (HV) over 36–54 months in preclinical Alzheimer's disease (AD). However, the extent to which Aβ+ and BDNF Val66Met is related to circulating markers of BDNF (e.g. serum) is unknown. We aimed to determine the effect of Aβ and the BDNF Val66Met polymorphism on levels of serum mBDNF, EM, and HV at baseline and over 18-months.
Non-demented older adults (n = 446) underwent Aβ neuroimaging and BDNF Val66Met genotyping. EM and HV were assessed at baseline and 18 months later. Fasted blood samples were obtained from each participant at baseline and at 18-month follow-up. Aβ PET neuroimaging was used to classify participants as Aβ– or Aβ+.
At baseline, Aβ+ adults showed worse EM impairment and lower serum mBDNF levels relative to Aβ- adults. BDNF Val66Met polymorphism did not affect serum mBDNF, EM, or HV at baseline. When considered over 18-months, compared to Aβ– Val homozygotes, Aβ+ Val homozygotes showed significant decline in EM and HV but not serum mBDNF. Similarly, compared to Aβ+ Val homozygotes, Aβ+ Met carriers showed significant decline in EM and HV over 18-months but showed no change in serum mBDNF.
While allelic variation in BDNF Val66Met may influence Aβ+ related neurodegeneration and memory loss over the short term, this is not related to serum mBDNF. Longer follow-up intervals may be required to further determine any relationships between serum mBDNF, EM, and HV in preclinical AD.
In this paper we undertake a quantitative analysis of the dynamic process by which ice underneath a dry porous debris layer melts. We show that the incorporation of debris-layer airflow into a theoretical model of glacial melting can capture the empirically observed features of the so-called Østrem curve (a plot of the melt rate as a function of debris depth). Specifically, we show that the turning point in the Østrem curve can be caused by two distinct mechanisms: the increase in the proportion of ice that is debris-covered and/or a reduction in the evaporative heat flux as the debris layer thickens. This second effect causes an increased melt rate because the reduction in (latent) energy used for evaporation increases the amount of energy available for melting. Our model provides an explicit prediction for the melt rate and the temperature distribution within the debris layer, and provides insight into the relative importance of the two effects responsible for the maximum in the Østrem curve. We use the data of Nicholson and Benn (2006) to show that our model is consistent with existing empirical measurements.
Recession of the Laurentide Ice Sheet from northern New Hampshire was interrupted by the Littleton-Bethlehem (L-B) readvance and deposition of the extensive White Mountain Moraine System (WMMS). Our mapping of this moraine belt and related glacial lake sequence has refined the deglaciation history of the region. The age of the western part of the WMMS is constrained to ~14.0–13.8 cal ka BP by glacial Lake Hitchcock varves that occur beneath and above L-B readvance till and were matched to a revised calibration of the North American Varve Chronology presented here. Using this age for when boulders were deposited on the moraines has enabled calibration of regional cosmogenic-nuclide production rates to improve the precision of exposure dating in New England. The L-B readvance coincided with the Older Dryas (OD) cooling documented by workers in Europe and the equivalent GI-1d cooling event in the Greenland Ice Core Chronology 2005 (GICC05) time scale. The readvance and associated moraines provide the first well-documented and dated evidence of the OD event in the northeastern United States. Our lake sediment cores show that the Younger Dryas cooling was likewise prominent in the White Mountains, thus extending the record of this event westward from Maine and Maritime Canada.
Social disability is a hallmark of severe mental illness yet individual
differences and factors predicting outcome are largely unknown.
To explore trajectories and predictors of social recovery following a
first episode of psychosis (FEP).
A sample of 764 individuals with FEP were assessed on entry into early
intervention in psychosis (EIP) services and followed up over 12 months.
Social recovery profiles were examined using latent class growth
Three types of social recovery profile were identified: Low Stable (66%),
Moderate-Increasing (27%), and High-Decreasing (7%). Poor social recovery
was predicted by male gender, ethnic minority status, younger age at
onset of psychosis, increased negative symptoms, and poor premorbid
Social disability is prevalent in FEP, although distinct recovery
profiles are evident. Where social disability is present on entry into
EIP services it can remain stable, highlighting a need for targeted
How does living in a battleground state during a presidential election affect an individual’s political engagement? We utilize a unique collection of 113 million Facebook status updates to compare users’ political discussion during the 2008 election. “Battleground” state users are significantly more likely to discuss politics in the campaign season than are users in uncompetitive “blackout” states. Posting a political status update—a form of day-to-day engagement with politics—mediates ∼20 percent of the relationship between exposure to political competition and self-reported voter turnout. This paper is among the first to use a massive quantity of social media data to explain the microfoundations of how people think, feel, and act on a daily basis in response to their political environment.
The PRODIGY trial (Prevention of long term social disability amongst
young people with emerging psychological difficulties, ISRCTN47998710) is
a pilot trial of social recovery cognitive–behavioural therapy
The PRODIGY qualitative substudy aimed to (a) explore individual
experiences of participating in the pilot randomised, controlled trial
(recruitment, randomisation, assessment) and initial views of therapy,
and (b) to explore perceived benefits of taking part in research
v. ethical concerns and potential risks.
Qualitative investigation using semi-structured interviews with thematic
Analysis revealed participant experiences around the key themes of
acceptability, disclosure, practicalities, altruism and engagement.
Participants in both trial arms perceived themselves as gaining benefits
from being involved in the study, above and beyond the intervention. This
has implications for the design of future research and services for this
client group, highlighting the importance of being flexible and an
individualised approach as key engagement tools.
The American Political Science Review recently published a critique of an article we published in the Journal of Politics in 2008. In that article we showed that variants of the genes 5HTT and MAOA were significantly associated with voter turnout in a sample of 2,300 subjects from the National Longitudinal Study of Adolescent Health. Here, we address the critique first by conducting a replication study using an independent sample of 9,300 subjects. This study replicates the gene-environment interaction of the 5HTT gene variant with church attendance, but not the association with MAOA. We then focus on the general argument of the critique, showing that many of its characterizations of the literature in genetics and in political science are misleading or incorrect. We conclude by illustrating the ways in which genopolitics has already made a lasting contribution to the field of political science and by offering guidelines for future studies in genopolitics that are based on state-of-the-art recommendations from the field of behavior genetics.
In interplanetary travel and high altitude flight, humans will be exposed to high energy charged particles from solar flares and galactic cosmic rays. These particles lose energy in a material by Coulomb interactions and nuclear collisions. In nuclear collisions, large amounts of energy are transferred and secondary particles are formed from both the projectile and the struck nucleus. A significant portion of these particles are neutrons which can only lose energy by collisions or reactions with a nucleus. Hydrogen-containing materials, such as polymers, are most effective in reducing the neutron energy. When reduced to very low energies, neutrons have a high probability of reacting with a nucleus. Such reactions are dangerous in the human body, and can cause electronic equipment failure. Low energy neutrons react particularly well with a stable isotope of boron, 10B. To test structural materials which contain both hydrogen to reduce the energy of neutrons and boron to absorb neutrons of reduced energy, samples of two polyimides were made which contained varying amounts of either amorphous boron powder or boron carbide whiskers. The polymers used were a thermoset, PETI-5 from Imitec, and a thermoplastic, K3B from Fiberite. Both materials were made in pure form and with up to 20% by weight of the boron additives. The addition of boron in either form did not change the thermal properties of these materials significantly. However, the compressive yield strength and the tensile strength were both affected by the addition of the boron materials. A neutron absorption test using a PuBe thermal neutron source showed that a 0.5 cm thick sample of K3B containing 15% amorphous boron powder absorbed over 90% of the incident neutrons.
The decision to vote has puzzled scholars for decades. Theoretical models predict little or no variation in participation in large population elections and empirical models have typically accounted for only a relatively small portion of individual-level variance in turnout behavior. However, these models have not considered the hypothesis that part of the variation in voting behavior can be attributed to genetic effects. Matching public voter turnout records in Los Angeles to a twin registry, we study the heritability of political behavior in monozygotic and dizygotic twins. The results show that a significant proportion of the variation in voting turnout can be accounted for by genes. We also replicate these results with data from the National Longitudinal Study of Adolescent Health and show that they extend to a broad class of acts of political participation. These are the first findings to suggest that humans exhibit genetic variation in their tendency to participate in political activities.
Phil C. Weigand has devoted his career to the anthropology and
archaeology of the most poorly known area of Mesoamerica, “an
enormous area of elaborate cultural development [that] has been
relegated to unimportance” (Weigand and Foster 1985:5). We refer, of course, to the
Occidente or West Mexico, roughly defined by the states of
Michoacán, Colima, Jalisco, and Nayarit, often including parts of
Guanajuato, Zacatecas, Sinaloa, and sometimes Guerrero. Over the course of
his career, Weigand has integrated data from archaeology, ethnohistory,
and ethnography to gain a better understanding of western Mesoamerica.
This Special Section is an homenaje to Phil that draws together
contributions by some of his friends and colleagues who have felt his
influence over the years.
Mammogenesis and lactation were induced in five multiparous, non-pregnant goats by treatment with oestrogen and progesterone for 11 d, followed by dexamethasone for 3 d. Reserpine was administered during the last 5 d. All five goats lactated, although milk yield was less than had been achieved in previous natural lactations. Mammary development was assessed in vivo, using magnetic resonance imaging. Although parenchyma volume increased by more than 6-fold overall, only 25% of this increase occurred during steroid treatment. Most development took place after the cessation of treatment, when milking commenced. Maximum size was not achieved until week 8 of the induced lactation, and was only 70% of normal parenchyma volume. After 18 weeks lactation the activities of three key milk synthetic enzymes were very similar to values previously found in natural lactations, and secretion efficiency (milk production per unit volume of parenchyma) was also similar to that of natural lactations. We conclude that the lower than normal milk yields were associated with incomplete proliferation of mammary tissue, rather than inadequate differentiation of individual secretory cells.
Four goats were studied from the end of their second lactation. One mammary gland of each goat was dried off just prior to the start of the third gestation, whilst the other gland was milked throughout gestation, with no dry period. At the end of gestation the continuously milked gland was significantly smaller than the gland that had been allowed a dry period. However, this difference did not persist beyond parturition and there was no significant difference between the milk yields of the two glands in the next lactation, although the continuously milked gland tended to have the higher yield. At 18 weeks of lactation, mammary parenchyma weight and secretory cell number were significantly greater in the continuously milked gland, but mammary enzyme activities did not differ between the two glands.
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