Simultaneous Determination of Neutron-Induced Fission and Radiative Capture Cross Sections from Decay Probabilities Obtained with a Surrogate Reaction.

Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of ^{239}Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and γ-emission probabilities for the ^{240}Pu(^{4}He,^{4}He^{'}) surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected γ-ray transitions, we measure the γ-emission probability. This enlarges the applicability of the surrogate-reaction method.

A magnetic shift register with out-of-plane magnetized layers.

Using out-of-plane magnetized layers, a lateral shift register made from discrete elements is demonstrated. By carefully designing the in-plane shape of the elements which make up the shift register, both the position of nucleation of new domains and the coercivity of the element can be controlled. The dipole field from a neighboring element, placed tens of nanometers away, creates a bias field on the nucleation site, which can be used to create a NOT gate. By chaining these NOT gates together, a shift register can be created where data bits consisting of neighboring layers with aligned magnetization are propagated synchronously under a symmetric applied magnetic field. The operation of a 16 element shift register is shown, including field coupled data injection.

Improvement of domain wall conduit properties in cobalt nanowires by global gallium irradiation.

Applications based on the movement of domain walls (DWs) in magnetic nanowires (NWs) require a good DW conduit behavior, i.e. a significant difference between DW nucleation and propagation fields. In this work, we have systematically studied how this property evolves in cobalt NWs grown by focused electron beam induced deposition (FEBID) as a function of global gallium irradiation, for irradiation doses up to 1.24 × 10(17) ions cm(-2). Whereas for high doses the DW conduit is lost, below 6.42 × 10(15) ions cm(-2) the difference between the two fields increases with irradiation, becoming up to ∼9 times larger than for non-irradiated wires, due to a strong increase in the nucleation field, while the propagation field remains approximately constant. This behavior stems from two effects. The first effect is a decrease in the magnetic volume of the parasitic halo around the NW, typically present in FEBID nanostructures, leading to the disappearance of weak nucleation centers. The second effect is the formation of a 20 nm outer shell with Co crystals about twice the size of those forming the NW core, causing a net increase of the local magnetocrystalline anisotropy. The results presented here are important for the potential use of magnetic NWs grown by FEBID in DW-based devices, and might also be of interest for magnetic NWs fabricated by other techniques.

Trace element content in tea brewed in traditional metallic and stainless steel teapots.

The migration of metals in tea brewed in metallic teapots was investigated. The teapots were obtained from North Africa stores in Brussels in 2005-2006 and in 2011. Chinese gunpowder green tea, the most commonly used tea in the Moroccan community, was used to prepare the tea. Tea brewed in metallic teapots was compared to tea brewed in a glass vessel in order to evaluate the contribution of the tea and the teapots to the metal concentrations in the brewed tea. Tea samples were also collected in Moroccan households and in tearooms in Brussels. The elements As, Cd, Pb, Sn, Mn, Fe, Cr, Co, Ni, Cr, Cu, Zn, and Al were analyzed by high-resolution sector field inductively coupled mass spectrometry. The relationship between the metal composition of the alloy of the teapot and the metal concentration in tea was also investigated. Migration of Pb and to a lesser amount Ni, Cu, and Zn was observed in brass teapots and migration of Cd from a number of stainless steel teapots was observed. The soldering connecting the sprout to the teapot was shown to be an important source of Pb to the tea. High levels of Mn and Al were also observed in the brewed tea and these elements where shown to originate from the tea itself. Metal exposure from tea drinking was calculated for different tea consumption levels and different metal concentration levels and compared to toxicological reference values.

Dynamic oscillations of coupled domain walls.

In domain wall (DW) excitation experiments, nonlinearity (NL) intrinsic to the DW dynamics is often hard to distinguish from perturbation due to the confining potential or DW distortion. Here we numerically investigate the dynamic oscillations of magnetostatically coupled DWs: a system well understood in the quasistatic limit. NL is observed, even for a harmonic potential, due to the intrinsic DW motion. This behavior is principally dependent on terms normally associated with the DW canonical momentum and is in contrast with a NL restoring potential. This NL is not observable in quasistatic measurements, relatively insensitive to the confining potential, and may be tuned by the nanowire parameters. The shown NLs are present in any DW restoring potential and must be accounted for when probing DW potential landscapes.

Fast domain wall motion in magnetic comb structures.

Modern fabrication technology has enabled the study of submicron ferromagnetic strips with a particularly simple domain structure, allowing single, well-defined domain walls to be isolated and characterized. However, these domain walls have complex field-driven dynamics. The wall velocity initially increases with field, but above a certain threshold the domain wall abruptly slows down, accompanied by periodic transformations of the domain wall structure. This behaviour is potentially detrimental to the speed and proper functioning of proposed domain-wall-based devices, and although methods for suppression of the breakdown have been demonstrated in simulations, a convincing experimental demonstration is lacking. Here, we show experimentally that a series of cross-shaped traps acts to prevent transformations of the domain wall structure and increase the domain wall velocity by a factor of four compared to the maximum velocity on a plain strip. Our results suggest a route to faster and more reliable domain wall devices for memory, logic and sensing.

Tunable remote pinning of domain walls in magnetic nanowires.

Domain wall (DW) pinning in ferromagnetic nanowires is in general a complex process. Distortions of the DW shape make quantitative agreement between modeling and experiment difficult. Here we demonstrate pinning using nanometer scale localized stray fields. This type of interaction gives well-characterized, tailorable potential landscapes that do not appreciably distort the DW. Our experimental results are in excellent quantitative agreement with an Arrhenius-Néel model of depinning--a result only possible when the modeled potential profile agrees fully with that experienced by the DW.

The effect of methylation on some biological parameters in Salmonella enterica serovar Typhimurium.

Cell growth is tightly coupled to DNA replication and its methylation [Proc Natl Acad Sci U S A 93 (1996) 12206-12211]. In a culture medium, growing of Salmonella Typhimurium (S. Typhimurium) mutant cells (dam⁻) decreased (2.5 fold) relative to the wild type strain (dam⁺). In this study, we show that the reason for this growth deficiency is due to the DNA methylation. The absence of a Dam methyltransferase protein results in poor growth efficiency and disturbs the synchrony of replication initiation in vivo, as evaluated by flow cytometry. On the other hand, we show that lack of methylation could increase the DNA response to thermal stress (decreasing the DNA melting temperature, T(m)), and the reason for this effect is due to the methylation status and not to the number of guanine and cytosine bases (G+C) in the duplex DNA. Our results show that methylation is an epigenetic factor that may play a key role in the cell growth, the synchrony of DNA replication [C R Biologies 330 (2007) 576-580] and the stress protection.

Magnetization reversal in individual cobalt micro- and nanowires grown by focused-electron-beam-induced-deposition.

We systematically study individual micro- and nanometric polycrystalline cobalt wires grown by focused-electron-beam-induced-deposition. The deposits were grown in a range of aspect ratios varying from 1 up to 26. The minimum lateral dimension of the nanowires was 150 nm, for a thickness of 40 nm. Atomic force microscopy images show beam-current-dependent profiles, associated with different regimes of deposition. The magnetization reversal of individual nanowires is studied by means of the spatially resolved magneto-optical Kerr effect. Abrupt switching is observed, with a systematic dependence on the wire's dimensions. This dependence of the coercive field is understood in magnetostatic terms, and agrees well with previous results on cobalt wires grown with different techniques. The influence of compositional gradients along the structural profile on the magnetic reversal is studied by using micromagnetic simulations. This work demonstrates the feasibility of using this technique to fabricate highly pure magnetic nanostructures, and highlights the advantages and disadvantages of the technique with respect to more conventional ones.

Effects of obstructive sleep apnea on cognitive function: a comparison between younger and older OSAS patients.

BACKGROUND AND PURPOSE: Patients with obstructive sleep apnea syndrome (OSAS) present cognitive deficits similar to those observed with aging. The aim of the study was to assess the effects of age on cognitive functions in OSAS patients. It was hypothesized that older OSAS patients will exhibit significant cognitive dysfunction relative to younger OSAS patients and controls. PATIENTS AND METHODS: Younger and older OSAS patients were compared to younger and older control subjects (age cut-off set at 50 yrs). Participants underwent a polysomnographic (PSG) and neuropsychological evaluation. Variables were analyzed by two-way analyses of variance (ANOVAs) with two factors: Group (control and OSAS) and Age (younger and older). Additionally, we evaluated the contribution of attentional deficits to cognitive dysfunction for each subgroup of patients by using Spearman correlation coefficients. RESULTS: No Group-by-Age interaction was found for any neuropsychological variables (p<0.05). However, main Group and Age effects were found. Correlations indicated that attentional deficits contributed importantly to a poorer cognitive performance in younger OSAS patients only (p<0.01). CONCLUSIONS: Our results are in agreement with those of the literature for both OSAS-related and aging-related cognitive deficits but did not demonstrate that age interacts with the effects of the OSAS condition to make those cognitive deficits worse.

Importance of determining the climatic domains of sheep breeds.

The main purpose of the study was to compare the capacity of the major sheep breeds in Morocco to cope with climate changes through the ranges of several climate parameters in which they can be found. We first delimitated the climatic 'domains' of each breed by constructing a database including altitude and climatic parameters (minima mean of the coldest month, maxima mean of the hottest month, annual rainfall, pluviothermic coefficient of Emberger Q 2, annual minima mean and annual maxima mean) on a 30-year period using the representative stations of each breed distribution. The overlap between each breed combination was quantified through a canonical analysis that extracted the most discriminant parameters. The variance analysis of each climatic parameter evidenced two breeds remarkable by their tolerance. The first one is the Timahdite, mainly settled in areas over 1100 m, which can tolerate the greatest variations in annual rainfall and pluviothermic coefficient. In spite of this feature, this breed is endangered owing to the decreasing quality of pastures. The second one is the D'man which apparently can support high variations in extreme temperatures. In fact, this breed is not well adapted to pastures and requires a special microclimate offered by oases. The information reported in this study will be the basis for the establishment of characterization and selection strategies for Moroccan sheep.

Age-at-onset in restless legs syndrome: a clinical and polysomnographic study.

OBJECTIVE: To determine the distribution of age-at-onset in a large cohort of patients with restless legs syndrome (RLS) and to compare clinical and polysomnographic characteristics of patients with early and late age-at-onset of RLS. METHODS: Two hundred and fifty patients with RLS were studied. Information on age-at-onset, etiology, familial history and symptoms severity of RLS was obtained. Age-at-onset density functions were determined from bootstrap methods and kernel density estimators. RESULTS: Age-at-onset showed a significant bimodal distribution with a large peak occurring at 20 years of age and a smaller peak in the mid-40s. Early- and late-onset RLS could be separated with a cut-off at 36 years of age. Distributions of age-at-onset differed as a function of presence/absence of a familial history and etiology of RLS. Age-at-onset clearly differentiated patients with a primary RLS (early onset) from those with secondary RLS. Finally, early-onset RLS was associated with increased RLS severity with higher indices of periodic leg movements in sleep (PLMS) associated with microarousals and periodic leg movements during wakefulness (PLMW). CONCLUSIONS: Early- and late-onset RLS could be distinguished depending on familial history and etiology of RLS. Our data suggest that different pathological processes are involved in these two groups, the early-onset group being highly genetically determined.

Zinc and cadmium accumulation among and within populations of the pseudometalophytic species Arrhenatherum elatius: implications for phytoextraction.

The purpose of this study was to investigate, under standard conditions, the bioaccumulation of zinc and cadmium in Arrhenatherum elatius, a perennial grass with a high biomass production. Nine populations of three different origins were tested: three metallicolous populations (mpop); three non-metallicolous populations (nmpop) and three populations developing on soils moderately metal polluted (medpop). We have found that bioaccumulation differs among these populations, with nmpop accumulating significantly more zinc (p<0.0001) and cadmium (p<0.0001) than mpop. Indeed, we have observed a concentration of 325 mg kg(-1) of zinc and 52 mg kg(-1) of cadmium in A. elatius shoots from mpop, whereas in nmpop, the concentration reached on average 524 mg kg(-1) zinc and 83 mg kg(-1) cadmium. In the same way, medpop accumulated as much zinc but more cadmium than nmpop. Moreover, the standard deviation of medpop was larger than the one for mpop and nmpop. Indeed, some A. elatius samples from medpop presented a high metal content whereas, others presented low concentrations in their shoots (ranging from 60 to 210 mg kg(-1) cadmium). Hence, these medpop exhibited a large variability among and within populations in accumulating zinc and cadmium in their shoots. Based on these results, the possibility of selecting A. elatius plants with the best accumulating capacity from medpop was proposed. We concluded that if the accumulation capacity is genetically controlled in A. elatius, this species fulfils this necessary condition for efficiently increasing species bioaccumulation by crossbreeding A. elatius plants with the higher accumulation capacity.

The mechanical response in a fluid of synthetic antiferromagnetic and ferrimagnetic microdiscs with perpendicular magnetic anisotropy.

In this article, we demonstrate the magneto-mechanic behavior in a fluid environment of perpendicularly magnetized microdiscs with antiferromagnetic interlayer coupling. When suspended in a fluid and under the influence of a simple uniaxial applied magnetic field sequence, the microdiscs mechanically rotate to access the magnetic saturation processes that are either that of the easy axis, hard axis, or in-between the two, in order to lower their energy. Further, these transitions enable the magnetic particles to form reconfigurable magnetic chains, and transduce torque from uniaxial applied fields. These microdiscs offer an attractive platform for the fabrication of fluid based micro- and nanodevices, and dynamically self assembled complex architectures.

Protocol optimization of sacroiliac joint MR Imaging at 3 Tesla: Impact of coil design and motion resistant sequences on image quality.

PURPOSE: To evaluate the impact of coil design and motion-resistant sequences on the quality of sacroiliac magnetic resonance imaging (MRI) examination in patients with spondyloarthropathy. PATIENTS AND METHODS: One hundred and twenty-one patients with suspected sacroiliitis and referred for MRI of the sacroiliac joints were retrospectively evaluated with MRI at 3-Tesla. There were 78 women and 43 men with a mean age of 36.7±11.5 (SD) years (range: 15.8-78.4 years). Conventional and motion-resistant fat-saturated fast-spin echo T2-weighted sequences were performed with two different coils. Image quality was subjectively evaluated by two independent readers (R1 and R2) using a four-point scale. Confidence in the identification of bone marrow edema pattern (BMEP) was also evaluated subjectively using a three-point scale. RESULTS: Phased array body coil yielded improved image quality compared to surface coil (14.1 to 30.4% for R1 and 14.6 to 25.7% for R2; P<0.0001). The impact of the sequence type on quality was also statistically significant (P=0.0046). BMEP was identified in 40 patients and best inter-reader agreement was obtained using the combination of phased-array body coil with motion-resistant T2-weighted sequence (kappa 0.990). The smallest number of indeterminate BMEP zones was seen on MRI set acquired with the phased-array body coil and motion-resistant T2-weighted sequence. CONCLUSION: Phased array body coil and motion-resistant T2-weighted sequences perform better than surface coil and conventional T2-weighted sequences for the evaluation of sacroiliac joints, increasing confidence in the identification of BMEP.

Long-term treatment with pramipexole in restless legs syndrome.

The aim of the present study was to look at the long-term efficacy and side effects profiles of pramipexole in a large cohort of drug naïve patients with regard to dopaminergic medications. In all, 195 consecutive restless legs syndrome (RLS) patients who were prescribed pramipexole more than 1 year previously, agreed to undergo a telephone interview to assess both the efficacy and side effects of pramipexole. Forty-three patients had discontinued pramipexole: 20 because of side effects, six because of a lack of efficacy, six for both and 11 for other reasons. Patients who continued pramipexole for more than 1 year (n = 152) reported a mean decrease in RLS symptoms severity of 80.9% (SD = 19.6%). At the onset of treatment, the most common side effects were nausea (30%), tiredness (9%), dizziness (8%), headache (4%), insomnia (3%), dry mouth (2%), difficulty to concentrate (1.3%) and sleepiness (0.7%), At 30 months, most patients (n = 124/152; 81.6%) reported an absence of side effects of pramipexole. None of the adverse effects occurred in more than 5% of patients at follow-up. The present study confirms, in a large cohort of unselected patients, that pramipexole is effective and safe in the long-term treatment of RLS.

Effects of glycerol on VLDL secretion by the isolated rat liver.

Stimulation of VLDL production by increasing fatty acid availability is now well established. However, a possible regulatory role of glycerol, another lipid precursor, in VLDL synthesis by the liver has not yet been substaniated. The present experiments investigate this problem using the isolated perfused rat liver. [14C] Glycerol uptake and metabolism were studied at two different glycerol concentrations: 1 mumol/perfusate (control) or 1.6 mmol/perfusate. VLDL production and lipid synthesis were investigated using [14C]leucine and several labelled fatty acids as precursors in control and glycerol-overloaded livers. Neoglycogenesis and lipogenesis from glycerol carbons are negligible in our conditions. The absolute amount of glycerol, but not the precentage, taken up by the liver, increased after raising its concentration in the perfusate. A major part of exogenous (plasmatic) glycerol was esterified with endogenous (non plasmatic) fatty acids. Incorporation of radioactive fatty acids into liver or plasma lipids was lower than in the the control group. Significant differences were observed between saturated and unsaturated fatty acids used as lipid precursors. Production of VLDL as assessed by radioactive leucine and fatty acid incorporation in the VLDL of the perfusate was depressed by glycerol. Glycerol partly inhibits the normal stimulation of VLDL production by plasmatic fatty acid overload.

A novel electrophoretic fractionation of Escherichia coli envelopes.

Particulate fractions of Escherichia coli have been submitted to electrophoretic fractionation in a buffer stabilized by sucrose gradient. Inner membrane and outer membrane were readily resolved. A combination of electrophoresis, fractional centrifugation and gel filtration can remove remaining contamination by ribosomes and cytoplasm. The presence of particles containing no phospholipids was detected after differential centrifugation. The nature of this fraction is unknown. The inner membrane exhibited heterogeneity on electrophoresis.

Degraded and stable phosphatidylglycerol in Escherichia coli inner and outer membranes, and recycling of fatty acyl residues.

The metabolic fate of membrane phospholipids in exponentially growing Escherichia coli was reexamined by incorporation and chase of labeled precursors: [32P]phosphate, [2-3H]glycerol and 3H-labeled fatty acids. It was found that the well-known turnover of phosphatidylglycerol lasted only about two generation times; after which period, the remaining labeled phosphatidylglycerol, approximately one-third of the total, was stable for at least the subsequent two generation times. The location of the stable phosphatidylglycerol pool remaining after the turnover in the outer and inner membrane was investigated. Both envelopes were found to contain stable phosphatidylglycerol so that the existence of a stable portion cannot be ascribed to its exclusive location in one leaflet. In some experiments, a small loss of labeled phosphatidylethanolamine was also observed, and upon fractionation this was found to occur exclusively in the outer membrane. [32P]Phosphate and [2-3H]glycerol labels of the degraded phospholipids were lost from lipid-soluble material, whereas labeled fatty acid, palmitate or oleate was reincorporated into newly synthesized phosphatidylethanolamine and phosphatidylglycerol, so that total fatty acid label remained constant in (membrane) phospholipid during chase. In view of the amount of glycerol lost, the recycling of the fatty acids under the form of diacylglycerols to phosphatidic acid does not appear to be the predominant pathway of reincorporation. After double labeling with [32P]phosphate and [3H]palmitate, followed by chase, a complete balance sheet of loss and reincorporation of fatty acid, in the three phospholipids, in the two envelopes could be established. Results indicate that fatty acid was reincorporated essentially in the inner membrane phospholipids. Movements of phospholipids and of fatty acids from one membrane to another and in the plane of each layer are discussed in the light of the results.

Lipid and lipoprotein synthesis in isolated and cultured hepatocytes from lean and obese Zucker rats.

Hepatocytes were isolated by EDTA perfusion of livers from lean (Fa/-) and obese (fa/fa) Zucker rats. Triacylglycerol (TG) and sn-glycerol 3-phosphate were increased in fa/fa hepatocytes, but free fatty acids, cholesterol and phospholipid concentrations were similar in both groups. In spite of an identical fatty acid uptake rate, glycerolipid synthesis was higher in obese compared to lean rat hepatocytes, and this difference remained for at least 2-3 days of culture. Triacylglycerol mass secretion was 2-fold higher in obese than in lean rat hepatocytes. This was confirmed by the higher incorporation of labeled glycerol and oleic acid into the medium TG fraction floating at density 1.006 g/ml. Density gradient ultracentrifugation of [14C]oleate-labeled lipoproteins showed that fa/fa hepatocytes secreted more TG-rich lipoproteins, and that 87% of the label was in the VLDL fraction compared with 67% in the medium of Fa/- hepatocytes. Decreased utilisation of leucine for protein synthesis in obese rat compared to lean rat hepatocytes was associated with enhanced leucine oxidation to CO2. [35S]Methionine incorporation showed an identical cell protein synthesis rate. Autoradiography after PAGE separation of secreted apolipoproteins (apoBh, Bl, apoA-VI, apoE, apoA-I, apoC) showed an identical pattern in both cell types.