Accounting for Life-Course Exposures in Epigenetic Biomarker Association Studies: Early Life Socioeconomic Position, Candidate Gene DNA Methylation, and Adult Cardiometabolic Risk

Recent studies suggest that epigenetic programming may mediate the relationship between early life environment, including parental socioeconomic position, and adult cardiometabolic health. However, interpreting associations between early environment and adult DNA methylation may be difficult because of time-dependent confounding by life-course exposures. Among 613 adult women (mean age = 32 years) of the Jerusalem Perinatal Study Family Follow-up (2007-2009), we investigated associations between early life socioeconomic position (paternal occupation and parental education) and mean adult DNA methylation at 5 frequently studied cardiometabolic and stress-response genes (ABCA1, INS-IGF2, LEP, HSD11B2, and NR3C1). We used multivariable linear regression and marginal structural models to estimate associations under 2 causal structures for life-course exposures and timing of methylation measurement. We also examined whether methylation was associated with adult cardiometabolic phenotype. Higher maternal education was consistently associated with higher HSD11B2 methylation (e.g., 0.5%-point higher in 9-12 years vs. ≤8 years, 95% confidence interval: 0.1, 0.8). Higher HSD11B2 methylation was also associated with lower adult weight and total and low-density lipoprotein cholesterol. We found that associations with early life socioeconomic position measures were insensitive to different causal assumption; however, exploratory analysis did not find evidence for a mediating role of methylation in socioeconomic position-cardiometabolic risk associations.

Training in Swallowing Prevents Aspiration Pneumonia in Stroke Patients with Dysphagia

This study investigated the frequency of aspiration pneumonia in conscious stroke patients fed by a family member and examined the effect of introducing training in swallowing techniques by nurses. A total of 96 consecutive patients presenting with dysphagia due to acute stroke were included in the study. Patients presenting between January 2000 and July 2003 ( n = 48) were fed orally by a family member given general nursing information (group A), whereas those presenting between August 2003 and March 2005 ( n = 48) were fed orally by an experienced nurse trained in specific swallowing techniques (group B). All patients were examined daily for the presence of aspiration pneumonia. The incidence of aspiration pneumonia was 33.3% in group A and 6.3% in group B ( P < 0.05). The incidence of aspiration pneumonia in dysphagic stroke patients who are orally fed is still high. Training in swallowing during oral feeding offers clear protection against pneumonia in conscious stroke patients.

[Influence of manganese exposure via intracerebral injection on behavioristics and substantia nigra dopaminergic neurons in rats]

OBJECTIVE

To investigate the changes in behavioristics, substantia nigra tyrosine hydroxylase (TH) immunoreactive cells, and ultrastructure of substantia nigra neurons in rats after manganese exposure via intracerebral injection.

METHODS

A total of 72 healthy male Sprague-Dawley rats were randomly divided into exposure group and control group, with 36 rats in each group. The stereotactic technique was used for injection of 1 μl MnCl2·4H2O (1 mol/L) into the corpus striatum in the exposure group, and the control group was injected with the same volume of normal saline. The changes in rotational behavior, number of TH immunoreactive cells in the substantia nigra, and ultrastructure of the substantia nigra induced by apomorphine were observed at 8 hours and 1, 3, 7, 15, and 30 days after injection, and this measure was compared with manganese exposure via intraperitoneal injection.

RESULTS

After apomorphine induction for 30 minutes, the exposure group showed a gradual increase in the number of rotations over the time of manganese exposure (F= 176.921, P<0.01) and a significantly higher number of rotations than the control group (F=482.654, P<0.01). The exposure group showed a gradual reduction in the mean A value of TH immunoreactive cells in the injured substantia nigra over the time of exposure (F=12.009, P<0.01) , and this value differed significantly between the injured substantia nigra in the exposure group and the contralateral substantia nigra in the exposure group and the injured side in the control group (F=36.131, P<0.01). At 3, 7, 15, and 30 days after exposure, the injured substantia nigra showed a significantly lower mean A value of TH immunoreactive cells than the contralateral side in the exposure group (all P<0.01). At 7, 15, and 30 days, the injured substantia nigra in the exposure group showed a significantly lower mean A value than the injured side in the control group (all P<0.01). After manganese exposure, substantia nigra neurons showed the changes including mitochondrial swelling, dilatation of the endoplasmic reticulum, and demyelination of nerve fibers in different stages, which suggested the dynamic process of dopaminergic neuron injuries. Compared with manganese exposure via intraperitoneal injection, manganese exposure via intracerebral injection can induce behavioral changes and injuries of the substantia nigra-striatum system more quickly.

CONCLUSION

Manganese exposure via intracerebral injection induces behavioral changes and injuries of substantia nigra dopaminergic neurons in rats within a short time.

Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera's capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantify lattice deformation and fracture; fracture is dominated by splitting cracks followed by wing cracks, and diffraction peaks are broadened likely due to mosaic spread. Our results demonstrate the potential of such multiscale measurements for studying high strain-rate phenomena at dynamic extremes.

Tensile Strength of Liquids: Equivalence of Temporal and Spatial Scales in Cavitation

It is well known that strain rate and size effects are both important in material failure, but the relationships between them are poorly understood. To establish this connection, we carry out molecular dynamics (MD) simulations of cavitation in Lennard-Jones and Cu liquids over a very broad range of size and strain rate. These studies confirm that temporal and spatial scales play equivalent roles in the tensile strengths of these two liquids. Predictions based on smallest-scale MD simulations of Cu for larger temporal and spatial scales are consistent with independent simulations, and comparable to experiments on liquid metals. We analyze these results in terms of classical nucleation theory and show that the equivalence arises from the role of both size and strain rate in the nucleation of a daughter phase. Such equivalence is expected to hold for a wide range of materials and processes and to be useful as a predictive bridging tool in multiscale studies.

Are Early-Life Socioeconomic Conditions Directly Related to Birth Outcomes? Grandmaternal Education, Grandchild Birth Weight, and Associated Bias Analyses

Grandmaternal education may be related to grandchild birth weight (GBW) through maternal early-life development; however, conventional regression models may be endogenously confounded. Alternative models employing explicit structural assumptions may provide incrementally clearer evidence. We used data from the US National Longitudinal Study of Adolescent to Adult Health (1995-2009; 1,681 mother-child pairs) to estimate "direct effects" of grandmaternal educational level (less than high school, high school diploma or equivalent, or college degree) at the time of the mother's birth on GBW, adjusted for maternal life-course factors: maltreatment as a child, education and income as an adult, prepregnancy overweight, and prenatal smoking. Using conventional and marginal structural model (MSM) approaches, we estimated 54-g (95% confidence interval: -14.0, 122.1) and 87-g (95% confidence interval: 10.9, 162.5) higher GBWs per increase in educational level, respectively. The MSM allowed simultaneous mediation by and adjustment for prepregnancy overweight. Estimates were insensitive to alternate structural assumptions and mediator parameterizations. Bias analysis suggested that a single unmeasured confounder would have to have a strong influence on GBW (approximately 150 g) or be greatly imbalanced across exposure groups (approximately 25%) to completely explain the findings. Coupling an MSM with sensitivity analyses provides some evidence that maternal early-life socioeconomic environment is directly associated with offspring birth weight.

DNA repair gene XRCC3 variants are associated with susceptibility to glioma in a Chinese population

The susceptibility to glioma is not well understood. It has been suggested that the X-ray cross complementing group 3 (XRCC3) gene influences the capacity to repair DNA damage, leading to increased glioma susceptibility. In this study, we evaluated the relationship between XRCC3 mutations and glioma risk. Genotypes were assessed in 389 Chinese glioma patients and 358 healthy controls. XRCC3 Thr241Met (rs861539) and 2 additional polymorphisms, rs3212112 (c.774+19T>G) and rs1799796 (c.562-14A>G), were directly sequenced. The frequency of the rs861539 T allele was significantly lower in the glioma group than in healthy controls [11.1 vs 17.7%, odds ratio = 0.62 (0.48-0.80), P < 0.001]; the frequencies of the CT or CT+TT genotypes differed between groups (18.5 vs 31%, 20.3 vs 33.2%, respectively). The frequency of the rs3212112 G allele was significantly higher in the glioma group than in healthy controls [15.8 vs 5.3%, odds ratio = 2.94 (2.07-4.17), P < 0.001]. The frequencies of the GT or TG+GG genotypes differed between groups (25.4 vs 7.8%, 28.5 vs 9.2%, respectively). This study demonstrates that the rs861539 and rs3212112 polymorphisms in the XRCC3 gene may influence the risk of glioma development in Chinese populations.

Security implications and governance of cognitive neuroscience

In recent years, significant efforts have been made toward elucidating the potential of the human brain. Spanning fields as disparate as psychology, biomedicine, computer science, mathematics, electrical engineering, and chemistry, research venturing into the growing domains of cognitive neuroscience and brain research has become fundamentally interdisciplinary. Among the most interesting and consequential applications to international security are the military and defense community's interests in the potential of cognitive neuroscience findings and technologies. In the United States, multiple governmental agencies are actively pursuing such endeavors, including the Department of Defense, which has invested over $3 billion in the last decade to conduct research on defense-related innovations. This study explores governance and security issues surrounding cognitive neuroscience research with regard to potential security-related applications and reports scientists' views on the role of researchers in these areas through a survey of over 200 active cognitive neuroscientists.

On-chip lithium cells for electrical and structural characterization of single nanowire electrodes

We present a transmission electron microscopy (TEM)-compatible, hybrid nanomachined, on-chip construct for probing the structural and electrical changes in individual nanowire electrodes during lithium insertion. We have assembled arrays of individual β-phase manganese dioxide (β-MnO2) nanowires (NWs), which are employed as a model material system, into functional electrochemical cells through a combination of bottom-up (dielectrophoresis) and top-down (silicon nanomachining) unit processes. The on-chip NWs are electrochemically lithiated inside a helium-filled glovebox and their electrical conductivity is studied as a function of incremental lithium loading during initial lithiation. We observe a dramatic reduction in NW conductivity (on the order of two to three orders in magnitude), which is not reversed when the lithium is extracted from the nanoelectrode. This conductivity change is attributed to an increase in lattice disorder within the material, which is observed from TEM images of the lithiated NWs. Furthermore, electron energy loss spectroscopy (EELS) was employed to confirm the reduction in valence state of manganese, which occurs due to the transformation of MnO2 to LixMnO2.

Association of serum vitamin D with symptoms of depression and anxiety in early pregnancy

Abstract Objective: To evaluate associations between early pregnancy 25-hydroxyvitamin D (25[OH]D) concentrations and antepartum depression and anxiety symptoms and potential modifiers thereof.

MATERIALS AND METHODS

In a pregnancy cohort (N=498), we examined cross-sectional associations of early pregnancy (mean=15.4 weeks gestation) serum 25[OH]D concentrations and depression and anxiety symptoms. Symptoms were measured using Depression, Anxiety, and Stress Scales (DASS-21) and Patient Health Questionnaire Depression Module (PHQ-9) instruments. Regression models were fit and effect modification by prepregnancy body mass index and leisure-time physical activity (LTPA) were assessed using interaction terms and stratified analyses.

RESULTS AND DISCUSSION

Mean 25[OH]D concentration was 34.4 ng/mL. Approximately 12% had "moderate" anxiety (score ≥ 10) and depression (score ≥ 10) symptoms by DASS-21 Anxiety and PHQ-9 instruments, respectively. A 1 ng/mL lower 25[OH]D was associated with 0.043 and 0.040 higher DASS-21 Anxiety and PHQ-9 Scores (p-values=0.052 and 0.029, respectively). Participants in the lowest quartile of 25[OH]D (<28.9 ng/mL) had 1.11 higher PHQ-9 scores than those in the highest quartile (≥ 39.5 ng/mL, p<0.05). However, associations were attenuated and statistically insignificant in fully adjusted models. Inverse associations of 25[OH]D with depression symptoms were significant among participants who reported no LTPA, but not among women who reported any LTPA (interaction p=0.018).

CONCLUSIONS

Our study provides modest evidence for inverse cross-sectional associations of early pregnancy maternal vitamin D concentrations with antepartum depression symptoms. We also observed that these associations may be modified by physical activity.

Top-up operation at Pohang Light Source-II

After three years of upgrading work, PLS-II (S. Shin, Commissioning of the PLS-II, JINST, January 2013) is now successfully operating. The top-up operation of the 3 GeV linear accelerator had to be delayed because of some challenges encountered, and PLS-II was run in decay mode at the beginning in March 2012. The main difficulties encountered in the top-up operation of PLS-II are different levels between the linear accelerator and the storage ring, the 14 narrow gap in-vacuum undulators in operation, and the full energy injection by 3 GeV linear accelerator. Large vertical emittance and energy jitter of the linac were the major obstacles that called for careful control of injected beam to reduce beam loss in the storage ring during injection. The following measures were taken to resolve these problems: (1) The high resolution Libera BPM (see http://www.i-tech.si) was implemented to measure the beam trajectory and energy. (2) Three slit systems were installed to filter the beam edge. (3) De-Qing circuit was applied to the modulator system to improve the energy stability of injected beam. As a result, the radiation by beam loss during injection is reduced drastically, and the top-up mode has been successfully operating since 19th March 2013. In this paper, we describe the experimental results of the PLS-II top-up operation and the improvement plan.

Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.

Inner retinal inhibition shapes the receptive field of retinal ganglion cells in primate

Abstract The centre–surround organisation of receptive fields is a feature of most retinal ganglion cells (RGCs) and is critical for spatial discrimination and contrast detection. Although lateral inhibitory processes are known to be important in generating the receptive field surround, the contribution of each of the two synaptic layers in the primate retina remains unclear. Here we studied the spatial organisation of excitatory and inhibitory synaptic inputs onto ON and OFF ganglion cells in the primate retina. All RGCs showed an increase in excitation in response to stimulus of preferred polarity. Inhibition onto RGCs comprised two types of responses to preferred polarity: some RGCs showed an increase in inhibition whilst others showed removal of tonic inhibition. Excitatory inputs were strongly spatially tuned but inhibitory inputs showed more variable organisation: in some neurons they were as strongly tuned as excitation, and in others inhibitory inputs showed no spatial tuning. We targeted one source of inner retinal inhibition by functionally ablating spiking amacrine cells with bath application of tetrodotoxin (TTX). TTX significantly reduced the spatial tuning of excitatory inputs. In addition, TTX reduced inhibition onto those RGCs where a stimulus of preferred polarity increased inhibition. Reconstruction of the spatial tuning properties by somatic injection of excitatory and inhibitory synaptic conductances verified that TTX-mediated inhibition onto bipolar cells increases the strength of the surround in RGC spiking output. These results indicate that in the primate retina inhibitory mechanisms in the inner plexiform layer sharpen the spatial tuning of ganglion cells.

Maternal birthweight is associated with subsequent risk of vitamin D deficiency in early pregnancy

BACKGROUND

Maternal low birthweight and vitamin D deficiency in pregnancy are associated with a similar spectrum of adverse pregnancy outcomes including pre-eclampsia and gestational diabetes. However, the relationship between maternal birthweight and subsequent vitamin D concentrations in early pregnancy is largely unknown.

METHODS

We assessed whether self-reported maternal birthweight was associated with risk of early pregnancy vitamin D deficiency (≤20 ng/mL) among a pregnancy cohort (n = 658). Serum 25-hydroxyvitamin D [25(OH)D] was measured using liquid chromatography-tandem mass spectroscopy.

RESULTS

Adjusting for maternal characteristics and month of blood draw, a 100-g higher maternal birthweight was associated with a 5.7% decreased risk of early pregnancy 25(OH)D deficiency [odds ratio (OR) = 0.94; 95% confidence interval (CI) 0.90, 0.99]. Low-birthweight (<2500 g) women were 3.7 times as likely to have early pregnancy 25(OH)D deficiency compared with normal-birthweight women [OR = 3.69; 95% CI 1.63, 8.34]. These relationships were not modified by either pre-pregnancy overweight status [body mass index (BMI) ≥25 kg/m(2)] or adulthood weight trajectory (BMI change ≥2 kg/m(2) from age 18 to pre-pregnancy).

CONCLUSIONS

Further research on shared developmental mechanisms that determine birthweight and vitamin D homeostasis may help identify targets and related preventative measures for adverse pregnancy and birth outcomes.

Induced maturation of hepatic progenitor cells in vitro

Hepatic progenitor cells (HPCs) are a potential cell source for liver cell transplantation but do not function like mature liver cells. We sought an effective and reliable method to induce HPC maturation. An immortalized HP14.5 albumin promoter-driven Gaussian luciferase (ALB-GLuc) cell line was established from HPCs isolated from fetal mouse liver of post coitus day 14.5 mice to investigate the effect of induction factors on ALB promoter. HP14.5 parental cells were cultured in DMEM with different combinations of 2% horse serum (HS), 0.1 µM dexamethasone (DEX), 10 ng/mL hepatic growth factor (HGF), and/or 20 ng/mL fibroblast growth factor 4 (FGF4). Trypan blue and crystal violet staining were used to assess cell proliferation with different induction conditions. Expression of hepatic markers was measured by semi-quantitative RT-PCR, Western blot, and immunofluorescence. Glycogen storage and metabolism were detected by periodic acid-Schiff and indocyanine green (ICG) staining. GLuc activity indicated ALB expression. The combination of 2% HS+0.1 µM Dex+10 ng/mL HGF+20 ng/mL FGF4 induced the highest ALB-GLuc activity. Cell proliferation decreased in 2% HS but increased by adding FGF4. Upon induction, and consistent with hepatocyte development, DLK, AFP, and CK19 expression decreased, while ALB, CK18, and UGT1A expression increased. The maturity markers tyrosine aminotransferase and apolipoprotein B were detected at days 3 and 6 post-induction, respectively. ICG uptake and glycogen synthesis were detectable at day 6 and increased over time. Therefore, we demonstrated that HPCs were induced to differentiate into functional mature hepatocytes in vitro, suggesting that factor-treated HPCs may be further explored as a means of liver cell transplantation.

Heterogeneity of cell death

Cell death constitutes a number of heterogeneous processes. Despite the dynamic nature of cell death, studies of cell death have primarily focused on apoptosis, and cell death has often been viewed as static events occurring in linear pathways. In this article we review cell death heterogeneity with specific focus on 4 aspects of cell death: the type of cell death; how it is induced; its mechanism(s); the results of cell death, and the implications of cell death heterogeneity for both basic and clinical research. This specifically reveals that cell death occurs in multiple overlapping forms that simultaneously occur within a population. Network and pathway heterogeneity in cell death is also discussed. Failure to integrate cell death heterogeneity within analyses can lead to inaccurate predictions of the amount of cell death that takes place in a tumor. Similarly, many molecular methods employed in cell death studies homogenize a population removing heterogeneity between individual cells and can be deceiving. Finally, and most importantly, cell death heterogeneity is linked to the formation of new genome systems through induction of aneuploidy and genome chaos (rapid genome reorganization).

SP600125, a JNK inhibitor, suppresses growth of JNK-inactive glioblastoma cells through cell-cycle G2/M phase arrest

SP600125 is a well studied inhibitor of c-Jun N-terminal kinase (JNK). Its direct biochemical effects on JNK-inactive tumor cells are usually ignored. In this study, we investigated the effects of SP600125 on JNK-inactive U251 human glioblastoma cells. Our results demonstrate that, 20 microM or more SP600125 can induce significant cell growth inhibition and cell-cycle G2/M phase arrest in U251 cells. Interestingly, we also found that SP600125 can stop the duplicated chromosomes from separating into two cells and the karyokinesis progression. Our study opened up a new perspective for further studies involved in JNK inhibitors or anti-glioma therapy.

F-spondin gene transfer improves memory performance and reduces amyloid-β levels in mice

Alzheimer's disease (AD) is the most prevalent form of dementia affecting the elderly. Evidence has emerged signifying that stimulation of the reelin pathway should promote neural plasticity and suppress molecular changes associated with AD, suggesting a potential therapeutic application to the disease. This was explored through the use of lentiviral vector-mediated overexpression of the reelin homolog, F-spondin, which is an activator of the reelin pathway. Intrahippocampal gene transfer of F-spondin improved spatial learning/memory in the Morris Water Maze and increased exploration of the novel object in the Novel Object Recognition test in wild-type mice. F-spondin overexpression also suppressed endogenous levels of amyloid beta (Aβ(42)) in these mice and reduced Aβ plaque deposition while improving synaptophysin expression in transgenic mouse models of AD. These data demonstrate pathologic and cognitive improvements in mice through F-spondin overexpression.

Fabrication of a nanostructure thermal property measurement platform

Measurements of the electrical and thermal transport properties of one-dimensional nanostructures (e.g. nanotubes and nanowires) are typically obtained without detailed knowledge of the specimen's atomic-scale structure or defects. To address this deficiency, we have developed a microfabricated, chip-based characterization platform that enables both transmission electron microscopy (TEM) of the atomic structure and defects as well as measurement of the thermal transport properties of individual nanostructures. The platform features a suspended heater line that physically contacts the center of a suspended nanostructure/nanowire that was placed using in situ scanning electron microscope nanomanipulators. Suspension of the nanostructure across a through-hole enables TEM characterization of the atomic and defect structure (dislocations, stacking faults, etc) of the test sample. This paper explains, in detail, the processing steps involved in creating this thermal property measurement platform. As a model study, we report the use of this platform to measure the thermal conductivity and defect structure of a GaN nanowire.

Hybrid Q-switched Yb-doped fiber laser

We investigate the performance of a hybrid Q-switched (HQS) fiber laser that is constructed with a low RF-power driven acousto-optic (AO) Q-switch and an AlGaInAs semiconductor saturable absorber. Compared to a pure passively Q-switched (PQS) fiber laser, the ratio of timing jitter to pulse period can be significantly reduced from 2% to 0.3% in the regime of far above threshold. On the other hand, the prelasing effect in a pure actively Q-switched fiber laser can be considerably improved. More importantly, the maximum pulse energy of the HQS fiber laser can be increased approximately 25% in comparison with the result of the PQS fiber laser. At a pump power of 24 W, the highest pulse energy is up to 0.56 mJ with the pulse duration of 50 ns at the repetition rate of 23 kHz.

Diurnal fluctuations in oxygen release from roots of Acorus calamus Linn in a modeled constructed wetland

Oxygen is known to be released from plant roots, but has seldom been quantified for wetland plants. Our study aims to quantify oxygen release from the roots of one wetland species in China, and use this knowledge as a basis for future modeling. We measured diurnal fluctuations in oxygen release from the roots of Acorus calamus Linn in a modeled constructed wetland (CW) using a titanium ([image omitted]) citrate buffer. Oxygen release was monitored every two hours. Maximum oxygen release was recorded in the range of 215.2-750.8 μmolg(-1)h(-1) and occurred around 15:00. The maximum value of photosynthetically active radiation (PAR) was in the range of 1281.8-1712.0 mmolm(-2)s(-1) and occurred around 13:00. Both the oxygen release rate and PAR were found to approach zero at night. Our results indicate that oxygen release depends largely on light intensity and exhibits a diurnal periodicity with release occurring only during daytime. Rate of root oxygen release varied during the daytime and this temporal variation was well described by the Gaussian function. While further validation is needed, we suggest that the Gaussian function may be used as the basis for modeling root oxygen release in natural and constructed wetlands.

Edge-mediated dislocation processes in multishell carbon nano-onions?

We report in situ electron microscopy observations of dislocation dissociation and annihilation processes in individual nanometer-sized carbon onions. Essential for these processes is the counterintuitive motion of the 1/2(0001) edge from the outer surface to the inner region, which cross-links or unlinks a large number of shells. The correlation with atomistic simulations and analysis of the energy which separates the strain and edge components indicates that this inward glide originates in the reduction of edge with each inwards glide step, an effect specific to the spherical topology.

Clogging pattern in vertical-flow constructed wetlands: insight from a laboratory study

Substrate clogging caused by the accumulation of the particulate solids is the worst operational problem for vertical-flow constructed wetlands (VFCW). In this paper, the effects of particulate solids distribution and their accumulation in the substrate with different gravel sizes were investigated. The results demonstrated that the clogging layer can be considered as two parts: one is the blanket-like deposition layer, and the other is the upper substrate clogging layer. Furthermore, the clogging process shall be partitioned as three stages of puncture phase for the pollutants; the formation of the blanket-like deposition layer; and the formation and compaction phase to the whole clogging layer. With reference to the clogging mechanism, it is believed that the particulate solids (< 100 microm) were absorbed firstly by electrostatic forces and van der Waals' forces. This is followed by the "bridging" made by the accumulated solids which act as a "sieve", thus further restricting larger particulate solids to flow through.

Determination of the absolute orientation of the retinylidene chromophore in purple membrane by a second-harmonic interference technique

The absolute direction of the retinal chromophore of bacterio-rhodopsin relative to the membrane plane is investigated by using an optical second-harmonic interference technique. Compared with the known adsorbed geometry of free retinylidene Schiff base on a glass substrate, our data indicate the beta-ionone ring of the chromophore of bacteriorhodopsin points away from the cytoplasmic surface of the purple membrane. The implication of this finding is discussed in light of other chemical and structural results on bacteriorhodopsin.

Superelongation and atomic chain formation in nanosized metallic glass

Bulk metallic glasses are brittle and fail with no plastic strain at room temperature once shear bands propagate. How do metallic glasses deform when the size is less than that of shear bands? Here we show that Al90Fe5Ce5 metallic glass with a size <20  nm can be extremely elongated to ∼200%. Remarkably, even an atomic chain was formed after sample necking, which was never observed in metallic glasses. The unexpected ductility may originate from the fast surface diffusion and the absence of shear band formation, and may guide the development of ductile metallic glasses for engineering applications.

Comparative studies for Cr4+:YAG crystal and AlGaInAs semiconductor used as a saturable absorber in Q-switched Yb-doped fiber lasers

We demonstrate comparative studies for Cr(4+):YAG crystal and AlGaInAs quantum-well (QW) used as a saturable absorbers in passively Q-switched Yb-doped fiber lasers. Both saturable absorbers were designed to be possessed of nearly the same initial transmission. Under a pump power of 24 W, the average output powers were up to 14.4 W and 13.8 W obtained with the AlGaInAs QWs and with the Cr(4+):YAG crystal, respectively. The maximum pulse energies obtained with the Cr(4+):YAG crystal and with the AlGaInAs QWs were found to be 0.35 mJ and 0.45 mJ, respectively.

High-pulse-energy, passively Q-switched Yb-doped fiber laser with AlGaInAs quantum wells as a saturable absorber

We demonstrate an efficient, high-pulse-energy, passively Q-switched Yb-doped fiber laser with AlGaInAs quantum wells (QWs) as a saturable absorber. The AlGaInAs QW material is designed to provide a large modulation change and a quite-low nonsaturable loss. At an incident pump power of 7.6 W, an average output power of 3.8 W, pulse energy of 300 microJ, pulse repetition rate of 12.5 kHz, and pulse duration of 30 ns was obtained.

Superplastic nanowires pulled from the surface of common salt

Superplastic nanowires were formed by touching the NaCl(100) surface with a Au tip in a transmission electron microscope. The nanowires were stretched < or =2.2 microm, or 280%, and bent >90 degrees upon compression, when showered with the electron beam. More surprisingly, no dislocations were observable during the elongation due to fast diffusion. Mechanical measurements in humid atmospheres suggest that salt nanowires also form in ambient environments.

Photoluminescence, thermal transport, and breakdown in joule-heated GaN nanowires

Thermal transport and breakdown in Joule-heated GaN nanowires is investigated using a combination of microphotoluminescence and in situ TEM characterization. The thermal conductivity of the nanowires is estimated to be <80 W/m.K, which is substantially below the bulk GaN value. Catastrophic breakdown in individual nanowires is observed to occur at a maximum temperature of approximately 1000 K, and nanowire morphology near the breakdown region indicates that failure occurs via thermal decomposition, a conclusion that is validated by in situ TEM images obtained during the failure process.

'Top-down' influences of ipsilateral or contralateral postero-temporal visual cortices on the extra-classical receptive fields of neurons in cat's striate cortex

In anesthetized and immobilized domestic cats, we have studied the effects of brief reversible inactivation (by cooling to 10 degrees C) of the ipsilateral or contralateral postero-temporal visual (PTV) cortices on: 1) the magnitude of spike-responses of neurons in striate cortex (cytoarchitectonic area 17, area V1) to optimized sine-wave modulated contrast-luminosity gratings confined to the classical receptive fields (CRFs) and 2) the relative strengths of modulation of CRF-induced spike-responses by gratings extending into the extra-classical receptive field (ECRF). Consistent with our previous reports (Bardy et al., 2006; Huang et al., 2007), inactivation of ipsilateral PTV cortex (presumed homologue of primate infero-temporal cortex) resulted in significant reversible changes (almost all substantial reductions) in the magnitude of spike-responses to CRF-confined stimuli in about half of the V1 neurones. Similarly, in half of the present sample, inactivation of ipsilateral PTV cortex resulted in significant reversible changes (in over 70% of cases, reduction) in the relative strength of ECRF modulation of the CRF-induced spike-responses. By contrast, despite the fact that receptive fields of all V1 cells tested were located within 5 degrees of representation of the zero vertical meridian, inactivation of contralateral PTV cortex only rarely resulted in significant (yet invariably small) changes in the magnitude of spike-responses to CRF-confined stimuli or significant (again invariably small) changes in the relative strength of ECRF modulation of spike-responses. Thus, the ipsilateral, but not contralateral, 'higher-order' visual cortical areas make significant contribution not only to the magnitude of CRF-induced spike-responses but also to the relative strengths of ECRF-induced modulation of the spike-responses of V1 neurons. Therefore, the feedback signals originating from the ipsilateral higher-order cortical areas appear to make an important contribution to contextual modulation of responses of neurons in the primary visual cortices.

Human membrane metallo-endopeptidase-like protein degrades both beta-amyloid 42 and beta-amyloid 40

Beta-amyloid (Abeta) degrading endopeptidases are thought to protect against Alzheimer's disease (AD) and are potentially therapeutic. Of particular interest are endopeptidases that are blocked by thiorphan and phosphoramidon (T/P), as these inhibitors rapidly induce Abeta deposition in rodents. Neprilysin (NEP) is the best known target of T/P; however neprilysin knockout results in only modest Abeta increases insufficient to induce deposition. Therefore, other endopeptidases targeted by T/P must be critical for Abeta catabolism. Another candidate is the T/P sensitive membrane metallo-endopeptidase-like protein (MMEL), a close homolog of neprilysin. The endopeptidase properties of beta and gamma splice forms of human MMEL were determined in HEK293T cells transduced with the human cDNAs for the two splice forms; this showed degradation of both Abeta(42) and Abeta(40) by hMMEL-beta but not hMMEL-gamma. hMMEL-beta activity was found at the extracellular surface with no significant secreted activity. hMMEL-gamma was not expressed at the extracellular surface. Finally, it was found that hMMEL cleaves Abeta near the alpha-secretase site (producing Abeta(1-17)>>Abeta(1-16)). These data establish hMMEL as a mediator of Abeta catabolism and raise the possibility of its involvement in the etiology of AD and as a target for intervention.

Analytical model for optimizing the parameters of an external passive Q-switch in a fiber laser

An analytical model is developed for optimizing two key parameters of an external passive Q-switch in a fiber laser from the criterion of the minimum average mode area inside the saturable absorber. One parameter is the optimum focal position that is analytically derived to be a function of the thickness and initial transmission of the saturable absorber. The other parameter is the optimum magnification of the reimaging optics that is analytically derived to be in terms of the numerical aperture and core radius of the laser fiber as well as the thickness and initial transmission of the saturable absorber. To demonstrate the utilization of the present model, an experiment on the subject of the passively Q-switched fiber laser is performed and optimized.

Passive Q switching of Er-Yb fiber laser with semiconductor saturable absorber

A high-performance AlGaInAs quantum-well saturable absorber is developed for passively Q-switched Er-Yb double-clad fiber lasers at 1560 nm. With an incident pump power of 13.5 W, an average output power of 1.26 W with a pulse repetition rate of 12 kHz is obtained. The maximum peak power is greater than 500 W.

Dislocation dynamics in multiwalled carbon nanotubes at high temperatures

Dislocation dynamics dictate the mechanical behavior of materials. Dislocations in periodic crystalline materials have been well documented. On the contrary, dislocations in cylindrical carbon nanotubes, particularly in multiwalled carbon nanotubes (MWCNTs), remain almost unexplored. Here we report that a room temperature 1/2<0001> sessile dislocation in a MWCNT becomes highly mobile, as characterized by its glide, climb, and the glide-climb interactions, at temperatures of about 2000 degrees C. The dislocation glide leads to the cross-linking of different shells; dislocation climb creates nanocracks; and the interaction of two 1/2<0001> dislocations creates kinks. We found that dislocation loops act as channels for mass transport. These dislocation dynamics are drastically different from that in conventional periodic crystalline materials due to the cylindrical, highly anisotropic structures of MWCNTs.

Real time microscopy, kinetics, and mechanism of giant fullerene evaporation

We report in situ high-resolution transmission electron microscopy observing the shrinkage of single-layer giant fullerenes (GF). At temperatures approximately 2000 degrees C, the GF volume reduces by greater than one 100-fold while the fullerene shell remains intact, evolving from a slightly polygonized to a nearly spherical shape with a smaller diameter. The number of carbon atoms in the GF decreases linearly with time until the small subbuckyball cage opens and rapidly disappears. Theoretical modeling indicates that carbon atoms are removed predominantly from the weakest binding energy sites, i.e., the pentagons, leading to the constant evaporation rate. The fullerene cage integrity is attributed to the collective behavior of interacting defects. These results constitute the first experimental evidence for the "shrink-wrapping" and "hot-giant" fullerene formation mechanisms.

A hot-wire probe for thermal measurements of nanowires and nanotubes inside a transmission electron microscope

A hot wire probe has been developed for use inside a transmission electron microscope to measure the thermal resistance of individual nanowires, nanotubes, and their contacts. No microfabrication is involved. The probe is made from a platinum Wollaston wire and is pretensioned to minimize the effects of thermal expansion, intrinsic thermal vibrations, and Lorentz forces. An in situ nanomanipulator is used to select a particular nanowire or nanotube for measurement, and contacts are made with liquid metal droplets or by electron-beam induced deposition. Detailed thermal analysis shows that for best sensitivity, the thermal resistance of the hot-wire probe should be four times that of the sample, but a mismatch of more than two orders of magnitude may be acceptable. Data analysis using the ratio of two ac signals reduces the experimental uncertainty. The range of detectable sample thermal resistances spans from approximately 10(3) to 10(9) KW. The probe can also be adapted for measurements of the electrical conductance and Seebeck coefficient of the same sample. The probe was used to study a multiwalled carbon nanotube with liquid Ga contacts. The measured thermal resistance of 3.3 x 10(7) KW had a noise level of approximately +/-3% and was repeatable to within +/-10% upon breaking and re-making the contact.

Semiconductor quantum-well saturable absorbers for efficient passive Q switching of a diode-pumped 946 nm Nd:YAG laser

InGaAs quantum wells and a Bragg mirror structure are grown on a GaAs substrate to simultaneously serve as a low-loss saturable absorber and an output coupler for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 946 nm. With an incident pump power of 9.2 W, the laser produces pulses of 38 ns duration with average pulse energy of as much as 20 microJ at a pulse repetition rate of 55 kHz.

In situ observation of quasimelting of diamond and reversible graphite-diamond phase transformations

Because of technique difficulties in achieving the extreme high-pressure and high-temperature (HPHT) simultaneously, direct observation of the structures of carbon at extreme HPHT conditions has not been possible. Banhart and Ajayan discovered remarkably that carbon onions can act as nanoscopic pressure cells to generate high pressures. By heating carbon onions to approximately 700 degrees C and under electron beam irradiation, the graphite-to-diamond transformation was observed in situ by transmission electron microscopy (TEM). However, the highest achievable temperature in a TEM heating holder is less than 1000 degrees C. Here we report that, by using carbon nanotubes as heaters and carbon onions as high-pressure cells, temperatures higher than 2000 degrees C and pressures higher than 40 GPa were achieved simultaneously in carbon onions. At such HPHT conditions and facilitated by electron beam irradiation, the diamond formed in the carbon onion cores frequently changed its shape, size, orientation, and internal structure and moved like a fluid, implying that it was in a quasimelting state. The fluctuation between the solid phase of diamond and the fluid/amorphous phase of diamond-like carbon, and the changes of the shape, size, and orientation of the solid diamond, were attributed to the dynamic crystallization of diamond crystal from the quasimolten state and the dynamic graphite-diamond phase transformations. Our discovery offers unprecedented opportunities to studying the nanostructures of carbon at extreme conditions in situ and at an atomic scale.

Enhanced ductile behavior of tensile-elongated individual double-walled and triple-walled carbon nanotubes at high temperatures

We report exceptional ductile behavior in individual double-walled and triple-walled carbon nanotubes at temperatures above 2000 degrees C, with tensile elongation of 190% and diameter reduction of 90%, during in situ tensile-loading experiments conducted inside a high-resolution transmission electron microscope. Concurrent atomic-scale microstructure observations reveal that the superelongation is attributed to a high temperature creep deformation mechanism mediated by atom or vacancy diffusion, dislocation climb, and kink motion at high temperatures. The superelongation in double-walled and triple-walled carbon nanotubes, the creep deformation mechanism, and dislocation climb in carbon nanotubes are reported here for the first time.

Passively Q-switched Yb3+:YCa4O(BO3)3 laser with InGaAs quantum wells as saturable absorbers

A diode-pumped Yb:YCOB laser at 1086 nm is passively Q switched by using InGaAs quantum wells as saturable absorbers and utilizing the Bragg mirror structure as an output coupler. With an absorbed pump power of 9.2 W the laser produces pulses of 100 ms duration with average pulse energy of as much as 165 microJ at a pulse repetition rate of 7 kHz.

High power passively Q-switched ytterbium fiber laser with Cr(4+):YAG as a saturable absorber

We report an efficient high-peak-power and high-average-power passively Q-switched ytterbium fiber laser with a Cr(4+):YAG crystal as a saturable absorber in an external-resonator configuration. At an incident pump power of 17.5 W, the passively Q-switched fiber laser produces an average power greater than 6.2 W with a pulse repetition rate of 48 kHz. The output pulses noticeably display a mode-locking phenomenon that leads to the maximum peak power to be higher than 20 kW.

InGaAs quantum-well saturable absorbers for a diode-pumped passively Q-switched Nd:YAG laser at 1123 nm

A low-loss semiconductor saturable absorber based on InGaAs quantum wells was developed for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 1123 nm. With an incident pump power of 16 W, an average output power of 3.1 W with a Q-switched pulse width of 77 ns at a pulse repetition rate of 100 kHz was obtained.

Kink formation and motion in carbon nanotubes at high temperatures

We report that kink motion is a universal plastic deformation mode in all carbon nanotubes when being tensile loaded at high temperatures. The kink motion, observed inside a high-resolution transmission electron microscope, is reminiscent of dislocation motion in crystalline materials: namely, it dissociates and multiplies. The kinks are nucleated from vacancy creation and aggregation, and propagate in either a longitudinal or a spiral path along the nanotube walls. The kink motion is related to dislocation glide and climb influenced by external stress and high temperatures in carbon nanotubes.

Real-time observation of tubule formation from amorphous carbon nanowires under high-bias Joule heating

The tubule formation process from amorphous carbon nanowires under high-bias-caused Joule heating was observed in real time in a high-resolution transmission electron microscope. The crystallization of the amorphous carbon nanowires occurred in two distinct ways: the formation of tubular graphitic basal planes parallel to the nanowire axis on the surface and the formation of nano-onions in the interior of the nanowire. The tubule formation mechanism is a process of solid-state atom diffusion at high temperatures. Energetically, the tubule formation is caused by the exceptionally low surface energy of the (0002) plane of graphite. Higher input power to the amorphous nanowires generally leads to improved graphitization and, in turn, to increased conductance. The results suggest that nanotube formation in the arc-discharge growth process may involve the formation and crystallization of amorphous carbon.

Shape evolution of lead telluride and selenide nanostructures under different hydrothermal synthesis conditions

Face-open nanoboxes of lead telluride and selenide have been synthesized by a simple hydrothermal method. Nano- and microcrystals of various morphologies, including microflowers, semi-microflowers, cubic nanoparticles, etc., have also been observed at different synthesis conditions. Temperature, time, and concentrations of various reactants play a major role in controlling the morphology and shape evolution of the product. This simple synthesis technique for the growth of various nano- and microstructures opens a new route to prepare hierarchical structures of a variety of binary semiconducting materials in a large quantity. A possible growth mechanism of such nano- and microstructures has been proposed.

AFM study of the effect of metronidazole on surface structures of sulfate-reducing bacteria

The effect of metronidazole (ME) on sulfate-reducing bacteria (SRB) was studied by atomic force microscopy (AFM) in this paper. Topography images of SRB cell show that after exposure to ME individual cell shape is sharply modified. Topography and phase images of SRB cell wall show that after exposure to ME not only the roughness of the cell wall increases but also the physical performance of SRB surface is changed to be uniform. AFM frictional loops show that after exposure to ME, SRB surface friction is increased remarkably.

Superplastic carbon nanotubes

The theoretical maximum tensile strain--that is, elongation--of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.

Observation of anomalously large spectral bandwidth in a high-gain self-amplified spontaneous emission free-electron laser

Observation of ultrawide bandwidth, up to 15% full-width, high-gain operation of a self-amplified spontaneous emission free-election laser (SASE FEL) is reported. This type of lasing is obtained with a strongly chirped beam (deltaE/E approximately 1.7%) emitted from the accelerator. Because of nonlinear pulse compression during transport, a short, high current bunch with strong mismatch errors is injected into the undulator, giving high FEL gain. Start-to-end simulations reproduce key features of the measurements and provide insight into mechanisms, such as angular spread in emitted photon and electron trajectory distributions, which yield novel features in the radiation spectrum.

Atomic-scale imaging of wall-by-wall breakdown and concurrent transport measurements in multiwall carbon nanotubes

We report the atomic-scale imaging with concurrent transport measurements of the breakdown of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezomanipulator. We found unexpectedly three distinct breakdown sequences: namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic.