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 email@example.com
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.
Evidence on whether nutritional supplementation affects physical activity (PA) during early childhood is limited. We examined the long-term effects of lipid-based nutrient supplements (LNS) on total PA, moderate-to-vigorous PA (MVPA) and sedentary behaviour (SB) of children at 4–6 years using an accelerometer for 1 week. Their mothers were enrolled in the International Lipid-based Nutrient Supplement-DYAD randomised controlled trial in Ghana, assigned to daily LNS or multiple micronutrients (MMN) during pregnancy through 6 months postpartum or Fe and folic acid (IFA) during pregnancy and placebo for 6 months postpartum. From 6 to 18 months, children in the LNS group received LNS; the other two groups received no supplements. Analysis was done with intention to treat comparing two groups: LNS v. non-LNS (MMN+ IFA). Of the sub-sample of 375 children fitted with accelerometers, 353 provided sufficient data. Median vector magnitude (VM) count was 1374 (interquartile range (IQR) 309), and percentages of time in MVPA and SB were 4·8 (IQR 2) and 31 (IQR 8) %, respectively. The LNS group (n 129) had lower VM (difference in mean −73 (95 % CI −20, −126), P = 0·007) and spent more time in SB (LNS v. non-LNS: 32·3 v. 30·5 %, P = 0·020) than the non-LNS group (n 224) but did not differ in MVPA (4·4 v. 4·7 %, P = 0·198). Contrary to expectations, provision of LNS in early life slightly reduced the total PA and increased the time in SB but did not affect time in MVPA. Given reduced social-emotional difficulties in the LNS group previously reported, including hyperactivity, one possible explanation is less restless movement in the LNS group.
There is limited evidence of the safety and impact of task-shared care for people with severe mental illnesses (SMI; psychotic disorders and bipolar disorder) in low-income countries. The aim of this study was to evaluate the safety and impact of a district-level plan for task-shared mental health care on 6 and 12-month clinical and social outcomes of people with SMI in rural southern Ethiopia.
In the Programme for Improving Mental health carE, we conducted an intervention cohort study. Trained primary healthcare (PHC) workers assessed community referrals, diagnosed SMI and initiated treatment, with independent research diagnostic assessments by psychiatric nurses. Primary outcomes were symptom severity and disability. Secondary outcomes included discrimination and restraint.
Almost all (94.5%) PHC worker diagnoses of SMI were verified by psychiatric nurses. All prescribing was within recommended dose limits. A total of 245 (81.7%) people with SMI were re-assessed at 12 months. Minimally adequate treatment was received by 29.8%. All clinical and social outcomes improved significantly. The impact on disability (standardised mean difference 0.50; 95% confidence interval (CI) 0.35–0.65) was greater than impact on symptom severity (standardised mean difference 0.28; 95% CI 0.13–0.44). Being restrained in the previous 12 months reduced from 25.3 to 10.6%, and discrimination scores reduced significantly.
An integrated district level mental health care plan employing task-sharing safely addressed the large treatment gap for people with SMI in a rural, low-income country setting. Randomised controlled trials of differing models of task-shared care for people with SMI are warranted.
We aimed to identify factors (child diet, physical activity; maternal BMI) associated with body composition of Ghanaian pre-school children.
Longitudinal analysis of the International Lipid-Based Nutrient Supplements (iLiNS)-DYAD-Ghana randomized trial, which enrolled 1320 pregnant women at ≤20 weeks’ gestation and followed them and their infants until 6 and 18 months postpartum, respectively. At follow-up, child age 4–6 years, we collected data on body composition (by 2H dilution), physical activity and diet, extracted dietary patterns using factor analysis, and examined the association of children’s percentage body fat with maternal and child factors by regression analysis.
Eastern Region, Ghana.
Children 4–6 years of age.
The analysis included 889 children with percentage body fat and dietary data at follow-up. We identified two major dietary patterns, a snacking and a cooked foods pattern. Percentage body fat was positively associated (standardized β (se)) with maternal BMI at follow-up (0·10 (0·03); P = 0·003) and negatively associated with physical activity (−0·15 (0·05); P = 0·003, unadjusted for child gender), but not associated with the snacking (0·06 (0·03); P = 0·103) or cooked foods (−0·05 (0·07); P = 0·474) pattern. Boys were more active than girls (1470 v. 1314 mean vector magnitude counts/min; P < 0·0001) and had lower percentage body fat (13·8 v. 16·9 %; P < 0·0001).
In this population, maternal overweight and child physical activity, especially among girls, may be key factors for addressing child overweight/obesity. We did not demonstrate a relationship between the dietary patterns and body fatness, which may be related to limitations of the dietary data available.
The formation of neutron stars in binary systems is often used to explain the nature of specific radio pulsars and characteristics of the pulsar population as a whole. We have investigated the extent to which such scenarios provide a self-consistent description of the pulsar population. Using a computer simulation, we modeled the evolution of the main sequence stellar population and compared the predicted neutron star population to the observed radio pulsar population, focusing our attention on the pulsar velocity distribution and the incidence of binary pulsars. These characteristics relate very directly to the binary nature of pulsar progenitors, and are not strongly dependent on models of pulsar magentic field and luminosity evolution.
The need to reproduce both the high velocities typical of pulsars and the low incidence of binary pulsars strongly constrains the formation of pulsars in binary systems. Unless one assumes that virtually all pulsars originate in close binary systems, the observed velocity distribution cannot result from the disruption of binary systems by symmetric supernova explosions; some additional acceleration process (e.g. asymmetric supernova mass ejection or asymmetries in pulsar radiation) must act during or soon after a pulsar's formation. It is possible to reproduce the velocity distribution by assuming that all pulsars are born in binary systems with initial orbital periods less than about 30 years. However, the predicted incidence of binaries is then too large by more than an order of magnitude, unless one also assumes that the process of mass transfer from the primary to the secondary is almost always non-conservative, or that the minimum mass necessary for a stripped helium core to explode as a supernova is larger (over 4 M⊙) than currently believed. Further analyses of the radio pulsar population, the X-ray binary population and the abundances of elements ejected in supernovae should help determine which of these alternatives is most reasonble. Additional studies of the main sequence stellar population, accounting more accurately for evolutionary and observational selection effects, will reduce the uncertainties in modeling the formation of the neutron star population.
It has also been suggested that the observed correlation between pulsar velocities and magnetic moments (see Cordes, these Proceedings) is induced by the differing evolutionary paths by which stars in binary systems form radio pulsars. Our simulation does not reproduce this correlation, and we do not find any paths likely to produce low velocity, low magnetic field neutron stars not in binary systems.
We are submitting a full description of our model and results to The Astrophysical Journal.
Dietary diversity, and in particular consumption of nutrient-rich foods including fruits, vegetables, nuts, beans and animal-source foods, is linked to greater nutrient adequacy. We developed a ‘dietary gap assessment’ to evaluate the degree to which a nation’s food supply could support healthy diets at the population level.
In the absence of global food-based dietary guidelines, we selected the Dietary Approaches to Stop Hypertension (DASH) diet as an example because there is evidence it prevents diet-related chronic disease and supports adequate micronutrient intakes. We used the DASH guidelines to shape a hypothetical ‘healthy’ diet for the test country of Cameroon. Food availability was estimated using FAO Food Balance Sheet data on country-level food supply. For each of the seven food groups in the ‘healthy’ diet, we calculated the difference between the estimated national supply (in kcal, edible portion only) and the target amounts.
In Cameroon, dairy and other animal-source foods were not adequately available to meet healthy diet recommendations: the deficit was −365 kcal (–1527 kJ)/capita per d for dairy products and −185 kcal (–774 kJ)/capita per d for meat, poultry, fish and eggs. Adequacy of fruits and vegetables depended on food group categorization. When tubers and plantains were categorized as vegetables and fruits, respectively, supply nearly met recommendations. Categorizing tubers and plantains as starchy staples resulted in pronounced supply shortfalls: −109 kcal (–457 kJ)/capita per d for fruits and −94 kcal (–393 kJ)/capita per d for vegetables.
The dietary gap assessment illustrates an approach for better understanding how food supply patterns need to change to achieve healthier dietary patterns.
In a perinatal cohort of women in urban and rural Turkey, we investigated associations between antenatal depressive symptoms and subsequent changes in perceived quality of key family relationships.
Of 730 women recruited in their third trimester (94.6% participation), 578 (79.2%) were reassessed at a mean of 4.1 (s.d. = 3.3) months after childbirth, 488 (66.8%) were reassessed at 13.7 (s.d. = 2.9) months, and 448 (61.4%) at 20.8 (s.d. = 2.7) months. At all four examinations, self-reported quality of relationship with the husband, mother and mother-in-law was ascertained using the Close Persons Questionnaire with respect to emotional support, practical support and negative aspects of the relationship. Antenatal depressive symptoms were defined using the Edinburgh Postnatal Depression Scale. A range of covariates in mixed models was considered including age, education, number of children, family structure, physical health, past emotional problems and stressful life events.
Key findings were as follows: (i) reported emotional and practical support from all three relationships declined over time in the cohort overall; (ii) reported emotional support from the husband, and emotional and practical support from the mother-in-law, declined more strongly in women with antenatal depressive symptoms; (iii) associations between depressive symptoms and worsening spouse relationship were more pronounced in traditional compared with nuclear families.
Antenatal depressive symptoms predicted marked decline in the quality of key relationships over the postnatal period. This may account for some of the contemporaneous associations between depression and worse social support, and may compound the risk of perinatal depression in subsequent pregnancies.
We have built a new radio astronomical receiving system designed specifically for very high precision timing and polarimetry of fast pulsars. Unlike most detectors currently used to study pulsars, this intrument does not square the received signal at the time of observation. Instead, voltages proportional to the instantaneous electric vectors of incoming signals are digitized, time-tagged, and recorded on high speed magnetic media. We have tested the system using a 5 MHz bandwidth signal with 2-bit digitization at the Greenbank 140 foot telescope. Full polarization information was obtained with a 0.2 μs time resolution. We have used this system to study the giant pulses emitted by PSR B0531+21 and PSR B1937+21, to determine high precision dispersion measures, and to perform high precision timing and polarimetry.
Differential 18-cm VLBI measurements of the position of PSR 1937+214 with respect to the quasar 1923+210 have been made to improve our knowledge of the offset between the planetary ephemeris reference frame and the extragalactic radio reference frame. Our preliminary frame-tie result (VLBI – Timing position) is +21 ± 2 milli-arcseconds in right ascension and +14 ± 9 milli-arcseconds in declination. We describe the data analysis methods used and compare our results with other radio interferometric position measurements of PSR 1937+214. Our results illustrate the value of combining the large collecting area of the Arecibo telescope with the Mk-III VLBI recording system.
The authors of the earlier version of this book succeeded in accomplishing the goals stated in their preface. Since it was written, Dynamics: Theory and Applications has served as a textbook for teaching graduate students a method of formulating dynamical equations of motion for mechanical systems. The method has proved especially useful for dealing with the complex multibody mechanical systems that in the twentieth and twenty-first centuries have challenged engineers in industry, government, and universities: the Galileo spacecraft sent to Jupiter, the International Space Station, and the robotic manipulator arms aiding astronauts on the Space Shuttle and International Space Station are but a few examples. Kane's method is systematic and easily taught, in a way that enables the student to be conversant with colleagues trained to apply traditional approaches found in the classical literature.
Although the fundamental aspects of the method have not changed during the past three decades, advances and refinements have been made in a number of areas. In certain cases the newer developments facilitate exposition of the topic at hand and lend themselves well to integration with material in the original textbook. The primary purpose of this text, then, is to make the benefits of this progress available for current courses in dynamics.
The preface to the earlier version (which immediately follows this Preface) includes a discussion of the organization of the original book and supporting rationale. Here, we give an overview of the modest alterations made to the earlier structure.
The initial chapter now begins with three brief sections that put the student into position to give a mathematical description of the orientation of a rigid body with respect to a reference frame, when the rigid body has been subjected to successive rotations. Inclusion of these sections provides a formal presentation of topics that typically were covered in classroom discussion. The final section of the first chapter is concerned with differentiation of a scalar function of vectors, which subsequently comes into play in Chapter 6. The original second chapter is divided in two; Chapter 2 deals solely with kinematics, and Chapter 3 is devoted to constraints. The separation focuses attention on the subject of constraints, where there are important distinctions to be made between Kane's method and the classical approaches.
The discipline of dynamics deals with changes of various kinds, such as changes in the position of a particle in a reference frame and changes in the configuration of a mechanical system. To characterize the manner in which some of these changes take place, one employs the differential calculus of vectors, a subject that can be regarded as an extension of material usually taught under the heading of the differential calculus of scalar functions. The extension consists primarily of provisions made to accommodate the fact that reference frames play a central role in connection with many of the vectors of interest in dynamics. A reference frame can be regarded as a massless rigid body, and a rigid body can serve as a reference frame. (A reference frame should not be confused with a coordinate system. Many coordinate systems can be embedded in a given reference frame.) The importance of reference frames in connection with change in a vector can be illustrated by considering the following example. Let A and B be reference frames moving relative to each other, but having one point O in common at all times, and let P be a point fixed in A, distinct from O and thus moving in B. Then the velocity of P in A is equal to zero, whereas the velocity of P in B differs from zero. Now, each of these velocities is a time derivative of the same vector, rOP, the position vector from O to P. Hence, it is meaningless to speak simply of the time derivative of rOP. Clearly, therefore, the calculus used to differentiate vectors must permit one to distinguish between differentiation with respect to a scalar variable in a reference frame A and differentiation with respect to the same variable in a reference frame B.
When working with elementary principles of dynamics, such as Newton's second law or the angular momentum principle, one needs only the ordinary differential calculus of vectors, that is, a theory involving differentiations of vectors with respect to a single scalar variable, generally the time. Consideration of advanced principles of dynamics, such as those presented in later chapters of this book, necessitates, in addition, partial differentiation of vectors with respect to several scalar variables, such as generalized coordinates and motion variables.