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.
Objectives: Past research suggests that youth with sex chromosome aneuploidies (SCAs) present with verbal fluency deficits. However, most studies have focused on sex chromosome trisomies. Far less is known about sex chromosome tetrasomies and pentasomies. Thus, the current research sought to characterize verbal fluency performance among youth with sex chromosome trisomies, tetrasomies, and pentasomies by contrasting how performance varies as a function of extra X number and X versus Y status. Methods: Participants included 79 youth with SCAs and 42 typically developing controls matched on age, maternal education, and racial/ethnic background. Participants completed the phonemic and semantic conditions of a verbal fluency task and an abbreviated intelligence test. Results: Both supernumerary X and Y chromosomes were associated with verbal fluency deficits relative to controls. These impairments increased as a function of the number of extra X chromosomes, and the pattern of impairments on phonemic and semantic fluency differed for those with a supernumerary X versus Y chromosome. Whereas one supernumerary Y chromosome was associated with similar performance across fluency conditions, one supernumerary X chromosome was associated with relatively stronger semantic than phonemic fluency skills. Conclusions: Verbal fluency skills in youth with supernumerary X and Y chromosomes are impaired relative to controls. However, the degree of impairment varies across groups and task condition. Further research into the cognitive underpinnings of verbal fluency in youth with SCAs may provide insights into their verbal fluency deficits and help guide future treatments. (JINS, 2018, 24, 917–927)
Reinforcement learning (RL) can be extremely effective in solving complex, real-world problems. However, injecting human knowledge into an RL agent may require extensive effort and expertise on the human designer’s part. To date, human factors are generally not considered in the development and evaluation of possible RL approaches. In this article, we set out to investigate how different methods for injecting human knowledge are applied, in practice, by human designers of varying levels of knowledge and skill. We perform the first empirical evaluation of several methods, including a newly proposed method named State Action Similarity Solutions (SASS) which is based on the notion of similarities in the agent’s state–action space. Through this human study, consisting of 51 human participants, we shed new light on the human factors that play a key role in RL. We find that the classical reward shaping technique seems to be the most natural method for most designers, both expert and non-expert, to speed up RL. However, we further find that our proposed method SASS can be effectively and efficiently combined with reward shaping, and provides a beneficial alternative to using only a single-speedup method with minimal human designer effort overhead.
Over the past decade, epigenetic analyses have made important contributions to our understanding of healthy development and a wide variety of adverse conditions such as cancer and psychopathology. There is increasing evidence that DNA methylation is a mechanism by which environmental factors influence gene transcription and, ultimately, phenotype. However, differentiating the effects of the environment from those of genetics on DNA methylation profiles remains a significant challenge. Monozygotic (MZ) twin study designs are unique in their ability to control for genetic differences because each pair of MZ twins shares essentially the same genetic sequence with the exception of a small number of de novo mutations and copy number variations. Thus, differences within twin pairs in gene expression and phenotype, including behavior, can be attributed in the majority of cases to environmental effects rather than genetic influence. In this article, we review the literature showing how MZ twin designs can be used to study basic epigenetic principles, contributing to understanding the role of early in utero and postnatal environmental factors on the development of psychopathology. We also highlight the importance of initiating longitudinal and experimental studies with MZ twins during pregnancy. This approach is especially important to identify: (1) critical time periods during which the early environment can impact brain and mental health development, and (2) the specific mechanisms through which early environmental effects may be mediated. These studies may inform the optimum timing and design for early preventive interventions aimed at reducing risk for psychopathology.
This study sought to better understand the patient s perspective of the experience of recovery from cancer that appeared to defy medical prognoses.
Fourteen cases of medically verified exceptional outcomes were identified. A qualitative approach, employing long narrative interviews was used. Data was analyzed using a cross case thematic analytic approach.
The major overarching theme was connections, both internal and external. Internal included connections with God or a higher power and with oneself. The external connections, the focus of this paper, included 1) personal connections with friends and family, 2) connections with the medical system: the physician, nurses and other staff, and 3) connections with other patients. They described the nature of these relationships and the importance of frequent contact with family and friends as providing significant emotional and instrumental support. They expressed confidence in receiving care from a reputable clinic, and with very little probing illustrated the importance of the relationship with their providers. They articulated the significance of the compassionate qualities of the physician and identified communication attributes of their physician that were important in establishing this connection. These attributes were demeanor, availability, honesty, sensitivity in the decision making process. They provided examples of positive connections with nurses and other staff as well as with other patients through their illness process.
Significance of results:
The importance of connections in these illness narratives was richly illustrated. These issues often are overlooked in clinical settings; yet they are of crucial importance to the health and well-being of the patients.
We model the OH megamaser emission from the luminous infrared galaxy IIIZw35 as arising from a narrow rotating starburst ring of radius 22 pc enclosing a mass of 7×106M⊙. We show how both the compact and apparently diffuse maser emission from this ring can arise from a single phase of unsaturated maser clouds amplifying background radio continuum. The masering clouds are estimated to have a diameter of <0.7 pc and internal velocity dispersion of ∽20 kms−1. We find that the clouds are neither self-gravitating nor pressure confined, and they could be magnetically confined or freely expanding. Their dispersal lifetimes may set the vertical thickness of the ring. For an estimated internal density of 3×103cm−3, cloud masses are of order 24 M⊙. The observed spectral features and velocity gradients indicate that the clouds must be outflowing and escaping the nucleus. The cloud mass outflow rate is estimated to be 0.8 M⊙yr−1, while the star formation rate is ∽19 M⊙yr−1. Associated ionised gas, possibly generated from dissipated clouds, provides free-free absorption along the source axis, explaining the observed East-West asymmetries. We show that the clumpiness of a maser medium can have a dramatic effect on what is observed even in a relatively low gain OH megamaser. Specifically, in IIIZw35 our clumpy maser model naturally explains the large line to continuum ratios, the large 1667MHz:1665MHz line ratios and the wide velocity dispersions seen in the compact maser spots. Other astrophysical masers showing both compact and apparently diffuse emission might be explained by similar clumpy structures.
We have connected viscoelastic recovery (healing) in sliding wear to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with a wide variety of chemical structures, except for polystyrene (PS). Examination of the effect of the indenter force level applied in sliding wear on the healing shows that recovery is practically independent of that level. Strain hardening in sliding wear was observed for all materials except PS, the exception attributed to brittleness. Therefore, we have formulated a quantitative definition of brittleness in terms of elongation at break and storage modulus. Further, we provide a formula relating the brittleness to sliding wear recovery; the formula is obeyed with high accuracy by all materials including PS. High recovery values correspond to low brittleness, and vice versa. Our definition of brittleness can be used as a design criterion for choosing polymers for specific applications.
We investigated the optical properties of pure copper irradiated by a
femtosecond laser pulse. Self-absorption of 50-fs laser pulses at 800 nm
and 400 nm wavelengths (below and above the interband absorption
threshold, respectively) is studied for peak laser intensities up to
1015 W/cm2. Theoretical description of laser
interaction with copper target is developed, solving numerically the
energy balance equations for electron and ion subsystems together with
Maxwell equations for laser radiation field inside the target. The theory
accounts for both intraband and interband absorption mechanisms. We
treated in detail the changes in electron structure and distribution
function with an increase in electron temperature, as well as the ensuing
changes in thermodynamic properties, collision frequencies, optical and
transport coefficients. Experimental work on self-absorption of
femtosecond laser pulses in copper targets at 800 nm and 400 nm
wavelengths is ongoing. Results for 800 nm wavelength are reported. Theory
and experiment are in good agreement.
The purpose of this article is to describe various
conditions on the parameters of pairs of nonhomogeneous
Poisson or pure birth processes under which the corresponding
epoch times or interepoch intervals are stochastically
ordered in various senses. We derive results involving
the usual stochastic order, the multivariate hazard rate
order, the multivariate likelihood ratio order, as well
as the dispersive and the mean residual life orders. A
sample of applications involving generalized Yule processes,
load-sharing models, and minimal repairs in reliability
theory illustrate the usefulness of the new results.
When a high power laser (1012 W/cm2)
irradiates a target, it induces a shock wave, which reaches
the (free) rear surface. The free surface is accelerated
and the shock wave is back-reflected as a rarefaction wave.
In the shock wave pressure regime involved here, melting
of the target during the shock or during the rarefaction
may occur. An optically recording velocity interferometric
system (ORVIS) has been developed to measure the time evolution
of the change in the reflectivity of the free surface.
Shock waves of the order of hundreds of kilobars are produced
in 50–125 μm thick Sn and Al foils, by a Nd:YAG
laser system with a wavelength of 1.06 μm, pulse width
of 7 ns (FWHM), and irradiance in the range
The changes in the reflectivity occur along two time scales:
a slow one, more than 17 ns in Al and more than 30 ns in Sn,
and a rapid one, less than 2.5 ns, in both materials. A
possible explanation for the sharp decreases in the time scale
is that melting occurs during the release of the free surface.
Oral melatonin (MLT) has been used by our Vancouver research group in the treatment of paediatric sleep disorders since 1991; slightly over 200 children, mainly with multiple disabilities, who frequently had seizures, have been treated. Three children with markedly delayed sleep onset due to recurring myoclonus were also referred for MLT treatment: two had non-epileptic, and one had epileptic and non-epileptic myoclonus. Low doses of oral MLT (3 to 5 mg) unexpectedly abolished their myoclonus and allowed them to sleep. There were no adverse effects. It appears that certain types of myoclonus, which might be resistant to conventional anticonvulsant medications, may respond to MLT but the mechanism of action is unclear. Further research on this novel treatment is urgently needed.
Arithmetic Asian options are difficult to price and hedge as they do not have closed-form analytic solutions. The main theoretical reason for this difficulty is that the payoff depends on the finite sum of correlated lognormal variables, which is not lognormal and for which there is no recognizable probability density function. We use elementary techniques to derive the probability density function of the infinite sum of correlated lognormal random variables and show that it is reciprocal gamma distributed, under suitable parameter restrictions. A random variable is reciprocal gamma distributed if its inverse is gamma distributed. We use this result to approximate the finite sum of correlated lognormal variables and then value arithmetic Asian options using the reciprocal gamma distribution as the state-price density function. We thus obtain a closed-form analytic expression for the value of an arithmetic Asian option, where the cumulative density function of the gamma distribution, G(d) in our formula, plays the exact same role as N(d) in the Black-Scholes/Merton formula. In addition to being theoretically justified and exact in the limit, we compare our method against other algorithms in the literature and show our method is quicker, at least as accurate, and, in our opinion, more intuitive and pedagogically appealing than any previously published result, especially when applied to high yielding currency options.
An experimental technique based on optical scattering to detect melting in release of strongly shocked materials is presented. This method is used to study the asymptotic behavior of the free surface of shock-loaded materials. After reflection of a shock wave from a metallic sample free surface, occurrence of a solid to liquid transition will induce a dynamic behavior such as mass ejection and development of instabilities. A study of the mass ejection due to laser-induced shock waves in aluminium, copper, and tin targets is presented. Shock waves of order of hundreds of kilobars to more than one megabar are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns FWHM focused to spot of 200 μm. The velocities, size, and topological structure of the ejected particles are measured. The radii of the ejecta are in the range 0.5–7 μm.
It is proved that if r* is the weak normalization of an integral domain r, then the weak normalization of the power series ring r[[x1,....xn]] is contained in R*[[X1,....Xn]]. Consequently, if R is a weakly normal integral domain, then R[[X1,....Xn]] is also weakly normal.
Preterm labour and its consequences are the major contributors to perinatal morbidity and mortality worldwide. The prevention of preterm labour and delivery is the single most important challenge to modern obstetrics today. Progress in this area has been hampered by lack of understanding of the basic mechanisms responsible for preterm labour. The implicit paradigm which has governed the study of parturition, is that term and preterm labour are fundamentally the same processes except for the gestational age at which they occur. Indeed, they share a common terminal pathway composed of uterine contractility, cervical dilatation and rupture of membranes. We proposed that while term labour is the result of physiological activation of this common terminal pathway, preterm labour and delivery is the consequence of pathological activation.1 Thus, preterm labour may be considered as the response of the fetomaternal unit to a variety of insults (e.g. chorioamnionitis, ischaemia, fetal growth restriction, etc.) (Fig 1) If these insults cannot be effectively handled in the context of a continuing pregnancy, then labour and delivery may occur.
Surgical manipulation of plastic prostheses using metal instruments is likely to produce surface damage and surface roughness which may compromise biocompatibility of implants due to tissue irritation and increased cellular or bacterial adhesion. There are virtually no data in the literature concerning the clinical occurrence and consequences of manipulative surface damage to implants. We have found that conventional high voltage scanning electron microscopy techniques (HVSEM) obscure surface defects on plastics due in large measure to beam energy “healing” by local melting. This paper reports the use of low voltage SEM (LVSEN) at low beam voltages (<1.5keV) and without the need for conductive carbon or Au/Pd coatings for examination of plastic device surfaces before and after normal surgical manipulation. Results for intraocular lens implants, a major human prosthesis, clearly demonstrate that standard surgical procedures can produce significant implant surface damage which may not be observed by normal SEN analysis. LVSEN has been shown to readily visualize such previously unobserved surface defects in model surgical manipulation experiments. These results have important implications for more reliable polymer surface characterization and for development of improved prosthetic devices, instruments, and implant surgery.
Email your librarian or administrator to recommend adding this to your organisation's collection.