Book chapters will be unavailable on Saturday 24th August between 8am-12pm BST. This is for essential maintenance which will provide improved performance going forwards. Please accept our apologies for any inconvenience caused.
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.
Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and three-dimensional particle-in-cell simulations. With the existence of a periodic structure on the target surface, the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density. The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target. Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron ‘islands’ formed by the surface plasma waves on the target surfaces. In other words, the radiation with the fundamental frequency is actually ‘surface emission’ on the target rear surface. Besides the intensity of the component with the fundamental frequency, the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target. The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces.
The East Kunlun Orogen (EKO) is the NW part of the Central China Orogenic Belt, which records the evolutionary history of the Proto- and Palaeo-Tethys Oceans from the Cambrian to the Triassic. An Early Palaeozoic eclogite belt has been recognized in recent years, which extends discontinuously for ∼500 km as three eclogite-bearing terranes. In this study, we report an integrated study of zircon grains from mica-schists accompanying the eclogites, in terms of mineral inclusions, U–Pb age systematics and P–T conditions. The presence of coesite is identified, as inclusions within the metamorphic domain of zircons, which provides unambiguous evidence for subducted terrigenous clastic rocks of the Proto-Tethys Ocean exhumed from coesite-forming depths. U–Pb dating of the metamorphic zircons yields a concordia age of 426.5 ± 0.88 Ma, which is likely to be the time of ultrahigh-pressure metamorphism in the Kehete terrane. P–T calculations suggest that metapelite may have experienced a clockwise P–T path with peak P/T conditions of 685 ± 41 °C and >28 kbar, and equilibrated at 482–566 °C and 5.6–8.9 kbar during subsequent exhumation. The high-pressure – ultrahigh-pressure (HP-UHP) metamorphic belt within the EKO may have formed by collision between the Qaidam Block and the South Kunlun Block, as a consequence of the closure of the Proto-Tethys Ocean.
To compare the epidemiologic features (e.g. settings and transmission mode) and patient clinical characteristics associated with outbreaks of different norovirus (Nov) strains, we retrospectively analysed data of Nov outbreaks occurring in Guangzhou, China from 2012 to 2018. The results suggested that outbreaks of Nov GII.2, GII.17 and GII.4 Sydney exhibited different outbreak settings, transmission modes and symptoms. GII.2 outbreaks mainly occurred in kindergartens, elementary and high schools and were transmitted mainly through person-to-person contact. By contrast, GII.4 Sydney outbreaks frequently occurred in colleges and were primarily associated with foodborne transmission. Cases from GII.2 and GII.17 outbreaks reported vomiting more frequently than those from outbreaks associated with GII.4 Sydney.
Objective: To examine trajectories of declines in learning and retention during the predementia phase of Alzheimer’s disease (AD) using the picture version of the Free and Cued Selective Reminding Test with Immediate Recall (pFCSRT+IR). Method: Learning was defined by the sum of free recall over three test trials. Retention was defined in two ways: by delayed free recall (DFR) and by savings; DFR adjusted for learning. The performances of 217 incident AD cases from the Baltimore Longitudinal Study of Aging (BLSA) were aligned based on the time that AD was first diagnosed. The predementia phase of learning and retention decline was assessed using change point models in which cognitive trajectories are described by a series of linear components with knots delineating times of accelerating decline. Results: Trajectories for both learning and DFR had two change points: the first at 6.58 (95% confidence intervals (CI): 6.56, 6.60) to 7.29 (95% CI: 6.13, 8.46) years before diagnosis followed by gradual decline over the next 4 years, and a second acceleration of decline 1.89 (0.56, 3.24) to 2.93 (95% CI: 1.56, 4.30) years before diagnosis. The change points for DFR were not significantly earlier in the predementia phase than the change points for learning. Savings had one change point, 5.3 (95% CI: 3.56, 7.04) years before diagnosis. Conclusion: Both learning and DFR showed similar profiles of decline in the years prior to the clinical diagnosis of AD. When delayed recall was adjusted for initial learning, the measure was less sensitive to early disease. (JINS, 2019, 25, 699–705)
Childhood maltreatment (CM) plays an important role in the development of major depressive disorder (MDD). The aim of this study was to examine whether CM severity and type are associated with MDD-related brain alterations, and how they interact with sex and age.
Within the ENIGMA-MDD network, severity and subtypes of CM using the Childhood Trauma Questionnaire were assessed and structural magnetic resonance imaging data from patients with MDD and healthy controls were analyzed in a mega-analysis comprising a total of 3872 participants aged between 13 and 89 years. Cortical thickness and surface area were extracted at each site using FreeSurfer.
CM severity was associated with reduced cortical thickness in the banks of the superior temporal sulcus and supramarginal gyrus as well as with reduced surface area of the middle temporal lobe. Participants reporting both childhood neglect and abuse had a lower cortical thickness in the inferior parietal lobe, middle temporal lobe, and precuneus compared to participants not exposed to CM. In males only, regardless of diagnosis, CM severity was associated with higher cortical thickness of the rostral anterior cingulate cortex. Finally, a significant interaction between CM and age in predicting thickness was seen across several prefrontal, temporal, and temporo-parietal regions.
Severity and type of CM may impact cortical thickness and surface area. Importantly, CM may influence age-dependent brain maturation, particularly in regions related to the default mode network, perception, and theory of mind.
Recent work has implicated one type of horizontal strabismus (exotropia) as a risk factor for schizophrenia. This new insight raises questions about a potential common developmental origin of the two diseases. Seasonality of births is well established for schizophrenia. Seasonal factors such as light exposure affect eye growth and can cause vision abnormalities, but little is known about seasonality of births in strabismus. We examined birth seasonality in people with horizontal strabismus in a retrospective study in Washoe County, Nevada, and re-examined similar previously obtained data from Osaka, Japan. We then compared seasonal patterns of births between strabismus, refractive error, schizophrenia and congenital toxoplasmosis. Patients with esotropia had a significant seasonality of births, with a deficit in March, then increasing to an excess in September, while patients with exotropia had a distinctly different pattern, with an excess of births in July, gradually decreasing to a deficit in November. These seasonalities were statistically significant with either χ2 or Kolmogorov–Smirnov-type statistics. The birth seasonality of esotropia resembled that for hyperopia, with an increase in amplitude, while the seasonality for myopia involved a phase-shift. There was no correlation between seasonality of births between strabismus and congenital toxoplasmosis. The pattern of an excess of summer births for people with exotropia was remarkably similar to the well-established birth seasonality of one schizophrenia subtype, the deficit syndrome, but not schizophrenia as a whole. This suggests a testable hypothesis: that exotropia may be a risk factor primarily for the deficit type of schizophrenia.
Muons produced by the Bethe–Heitler process from laser wakefield accelerated electrons interacting with high
materials have velocities close to the laser wakefield. It is possible to accelerate those muons with laser wakefield directly. Therefore for the first time we propose an all-optical ‘Generator and Booster’ scheme to accelerate the produced muons by another laser wakefield to supply a prompt, compact, low cost and controllable muon source in laser laboratories. The trapping and acceleration of muons are analyzed by one-dimensional analytic model and verified by two-dimensional particle-in-cell (PIC) simulation. It is shown that muons can be trapped in a broad energy range and accelerated to higher energy than that of electrons for longer dephasing length. We further extrapolate the dependence of the maximum acceleration energy of muons with the laser wakefield relativistic factor
and the relevant initial energy
. It is shown that a maximum energy up to 15.2 GeV is promising with
on the existing short pulse laser facilities.
The consequences of urbanisation for Earth's biogeochemical cycles are largely unexplored. Copper (Cu) in urban soils is being accumulated mainly due to anthropogenic activities under rapid urbanisation. The increasing Cu concentrations may contribute to altering soil nitrogen (N) cycling in urban ecosystems through modulating denitrification processes. This research aims to identify how Cu impacts urban soil denitrification functions and denitrifier abundance. An urban park soil with a background total Cu concentration of 7.9μgg–1 was incubated anaerobically with different Cu amendments (10, 20, 40, 80 and 160μg Cu g–1 soil), similar to prevalent Cu contents in urban soils. We evaluated the soil denitrification functions using the acetylene (C2H2) inhibition method and assessed the denitrifier abundance by quantitative polymerase chain reaction (qPCR) analyses of denitrifying marker genes (nirK, nirS and nosZ). At the function level, we observed that both the potential soil denitrification activity and the N2O emission rate due to denitrification were significantly (P<0.05) inhibited by Cu; even the lowest Cu addition (10μg Cu g–1 soil) drastically affected the denitrification function. Moreover, Cu significantly (P<0.05) decreased the abundance of nirK and nirS genes at the additions of 160μg Cu g–1 soil and 40μg Cu g–1 soil, respectively, whereas it had no clear impact on nosZ gene copies. Further correlation analyses revealed that the potential denitrification activity was positively correlated to the copy numbers of nirK and nirS genes, but it was not correlated to nosZ gene abundance. These findings indicate that Cu additions inhibited soil denitrification function and decreased denitrifier abundance in the investigated urban park soil. Our results suggest that Cu accumulation in urban soils, resulting from urbanisation, may generally influence denitrification in urban ecosystems.
Sinonasal malignant melanoma is a relatively rare malignancy with poor prognosis, and effective treatments remain elusive. This analysis aimed to explore whether post-operative radiotherapy conferred any survival advantages in patients with this disease when compared with surgery alone.
Published studies were identified by searching four electronic databases. The endpoints evaluated were: rates of overall survival, disease-free survival and local control.
Twenty-eight studies including 1392 patients were identified. The results indicated that post-operative radiotherapy led to a significantly better three-year overall survival rate (p = 0.02), and suggested a borderline significant benefit for five-year overall survival (p = 0.05), when compared with surgery alone. However, no statistical advantage was found for disease-free survival, local control or one-year overall survival.
This meta-analysis indicated that adjuvant radiotherapy prolonged survival, but showed no benefit for disease-free survival or local control.
To characterise subjective symptoms in patients undergoing surgical repair of superior semicircular canal dehiscence.
Questionnaires assessing symptom severity and impact on function and quality of life were administered to patients before superior semicircular canal dehiscence surgery, between June 2011 and March 2016. Questionnaire sections included general quality of life, internal amplified sounds, dizziness and tinnitus, with scores of 0–100 points.
Twenty-three patients completed the questionnaire before surgery. Section scores (mean±standard deviation) were: 38.2 ± 25.2 for general quality of life, 52.5 ± 23.9 for internal amplified sounds, 35.1 ± 28.8 for dizziness, 33.3 ± 30.7 for tinnitus, and 39.8 ± 22.2 for the composite score. Cronbach's α statistic averaged 0.93 (range, 0.84–0.97) across section scores, and 0.83 for the composite score.
The Gopen–Yang Superior Semicircular Canal Dehiscence Questionnaire provides a holistic, patient-centred characterisation of superior semicircular canal dehiscence symptoms. Internal consistency analysis validated the questionnaire and provided a quantitative framework for further optimisation in the clinical setting.
The distribution of human papillomaviruses (HPVs) must be understood for the control and prevention of cervical cancer. Community-based Papanicolaou and HPV DNA tests were performed on 41 578 women. The prevalences of HPV genotypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68 were assessed. In total, 10% women were infected/co-infected by these HPVs. The infection rate increased from 7.1% in women aged ⩽30 years to 10.4% in those aged 50–60 years, and then decreased slightly to 9.9% in those aged >60 years. The HPV 16 and 58 positivity rates were significantly higher among women with high-grade squamous intraepithelial lesions (HSILs) than among those with cervicitis/negativity for intraepithelial lesion or malignancy (NILM) or low-grade SILs (LSILs). The HPV 18, 52 and 68 infection rates were significantly lower in women with HSILs than in those with NILM or LSILs. The proportion of women infected by multiple HPV strains was higher among those with HSILs. The proportions of the five most common genotypes, HPV 16, 18, 33, 52 and 58, increased with the number of co-infecting strains. HPV 16 and 58 were the high-risk HPVs in the Shanghai community and should be the focus in HPV screening and vaccination.
Aiming at three-dimensional (3D) terminal guidance problem, a novel guidance model is established in this paper, in which line-of-sight (LOS) range is treated as an independent variable, describing the relative motion between the vehicle and the target. The guidance model includes two differential equations that describe LOS’s pitch and yaw motions in which the pitch motion is separately decoupled. This model avoids the inaccuracy of simplified two-dimensional (2D) guidance model and the complexity of 3D coupled guidance model, which not only maintains the accuracy but also simplifies the guidance law design. The application of this guidance model is studied for optimal re-entry guidance law with impact angle constraint, which is presented in the form of normal overload. Compared with optimal guidance laws based on traditional guidance model, the proposed one based on novel guidance model is implemented with the LOS range instead of time-to-go, which avoids the problem of the time-to-go estimation of traditional optimal guidance laws. Finally, the correctness and validity of the guidance model and guidance law are verified by numerical simulation. The guidance model and guidance law proposed in this paper provide a new way for the design of terminal guidance.
Full-scale simulations of a (Magnetorheological) MR damper are carried out for revealing its hysteretic behaviors associated with implementation of semi-active control using the routine of computational fluid dynamics. By virtue of the structural symmetry of the MR damper, a two-dimensional configuration for finite element simulation is built up. Herschel-Bulkley model is employed to represent the property of the MR fluid, of which the control parameters and their relevances to the input current are addressed. Typical cases involving sinusoidal and irregular displacements, steady and transient currents loaded upon the MR damper are investigated. Numerical investigations reveal that the damper force has a positive correlation with input current, excitation amplitude and excitation frequency. The full-scale simulation is proved to exhibit a sound accuracy through the validation of experimental data. It provides a logical manner revealing the true performance of MR dampers under desirable operating modes in practice, and can be readily integrated with the gain design of the associated semi-actively controlled structure. This progress bypasses the technical challenge inherent in the traditional tests with low-frequency cyclic loadings due to the limitation of experimental setup. Besides, comparative study between two-dimensional and three-dimensional configuration simulations of the MR damper shows that former has a better applicability, which can be carried out on a low-cost platform.
Good canopy structure is essential for optimal maize (Zea mays L.) production. However, creating appropriate maize canopy structure can be difficult, because the characteristics of individual plants are altered by changes in plant age, density and interactions with neighbouring plants. The objective of the current study was to find a reliable method for building good maize canopy structure by analysing changes in canopy structure, light distribution and grain yield (GY). A modern maize cultivar (ZhengDan958) was planted at 12 densities ranging from 1.5 to 18 plants/m2 at two field locations in Xinjiang, China. At the silking stage (R1), plant and ear height increased with plant density as well as leaf area index (LAI), whereas leaf area per plant decreased logarithmically. The fraction of light intercepted by the plant (F) increased with increasing plant density, but the light extinction coefficient (K) decreased linearly from 0.61 to 0.39. Taking the optimum value of F (95%) as an example, and using measured values of K for each plant density at R1 and the equation from Beer's law, the corresponding (theoretical) LAI for each plant density was calculated and optimum plant density (9.72 plants/m2) obtained by calculating the difference between theoretical LAIs and actual observations. Further analysis showed that plant density ranging from 10.64 to 11.55 plants/m2 yielded a stable GY range. Therefore, taking into account the persistence time for maximum LAI, the plant density required to obtain an ideal GY maize canopy structure should be increased by 10–18% from 9.72 plants/m2.
In salmon farming, the scarcity of fish oil has driven a shift towards the use of plant-based oil from vegetable or seed, leading to fish feed low in long-chain PUFA (LC-PUFA) and cholesterol. Atlantic salmon has the capacity to synthesise both LC-PUFA and cholesterol, but little is known about the regulation of synthesis and how it varies throughout salmon life span. Here, we present a systemic view of lipid metabolism pathways based on lipid analyses and transcriptomic data from salmon fed contrasting diets of plant or fish oil from first feeding. We analysed four tissues (stomach, pyloric caeca, hindgut and liver) at three life stages (initial feeding 0·16 g, 2·5 g fingerlings and 10 g juveniles). The strongest response to diets higher in plant oil was seen in pyloric caeca of fingerlings, with up-regulation of thirty genes in pathways for cholesterol uptake, transport and biosynthesis. In juveniles, only eleven genes showed differential expression in pyloric caeca. This indicates a higher requirement of dietary cholesterol in fingerlings, which could result in a more sensitive response to plant oil. The LC-PUFA elongation and desaturation pathway was down-regulated in pyloric caeca, probably regulated by srebp1 genes. In liver, cholesterol metabolism and elongation and desaturation genes were both higher on plant oil. Stomach and hindgut were not notably affected by dietary treatment. Plant oil also had a higher impact on fatty acid composition of fingerlings compared with juveniles, suggesting that fingerlings have less metabolic regulatory control when primed with plant oil diet compared with juveniles.
Background: The role of extent of surgical resection (EOR) on clinical outcomes in patients with low-grade glioma requires further examination. Methods: We systematically searched MEDLINE, Embase, and the Cochrane Library for studies published between January 1, 1990 and January 5, 2018 on predefined patient outcomes regarding different EOR of low-grade glioma. Results: Our literature search yielded 60 studies including 13,289 patients. Pooled estimates of overall survival showed an increase from 3.79 years (95% CI, 2.37–5.22) in the biopsy group to 6.68 years (95% CI, 4.19–9.16) in STR to 10.65 years (95% CI, 6.78–14.52) in GTR. When compared to STR, GTR prolonged progression-free survival by 2.08 years (95% CI, 0.26–3.89; P=0.025). Pooled estimates of seizure control showed an improvement from 47.8% (95% CI, 26.7–69.6) with biopsy to 54.2% (95% CI, 48.7–59.6) with STR to 81.0% (95% CI, 74.6–86.2) with GTR. Compared to STR, GTR delayed malignant transformation (RR, 0.43; 95% CI, 0.20–0.93; P=0.032), without increasing postoperative mortality (RR, 0.38; 95% CI, 0.07–1.97; P=0.250) or morbidity (RR, 1.22; 95% CI, 0.65–2.28; P=0.540). Conclusions: Among patients with low grade gliomas, higher degrees of safe EOR, were associated with longer overall and progression-free survival, better seizure control, and delayed malignant transformation, without increased mortality or morbidity.