An electron holography study of perpendicular magnetic tunnel junctions nanostructured by deposition on pre-patterned conducting pillars.

The fabrication of multi-gigabit magnetic random access memory (MRAM) chips requires the patterning of magnetic tunnel junctions at very small dimensions (sub-30 nm) and a very dense pitch. This remains a challenge due to the difficulty in etching magnetic tunnel junction stacks. We previously proposed a strategy to circumvent this problem by depositing the magnetic tunnel junction material on prepatterned metallic pillars, resulting in the junction being naturally shaped during deposition. Upon electrical contact, the deposit on top of the pillars constitutes the magnetic storage element of the memory cell. However, in this process, the magnetic material is also deposited in the trenches between the pillars that might affect the memory cell behaviour. Here we study the magnetic interactions between the deposit on top of the pillars and in the trenches by electron holography, at room temperature and up to 325 °C. Supported by models, we show that the additional material in the trenches is not perturbing the working principle of the memory chip and can even play the role of a flux absorber which reduces the crosstalk between neighboring dots. Besides, in the studied sample, the magnetization of the 1.4 nm thick storage layer of the dots is found to switch from out-of-plane to an in-plane configuration above 125 °C, but gradually decreases with temperature. Electron holography is shown to constitute a very efficient tool for characterizing the micromagnetic configuration of the storage layer in MRAM cells.

Measurement of the Curvature-Dependent Surface Tension in Nucleating Colloidal Liquids.

The curvature dependence of the surface tension is central to the nucleation of liquids, but remains difficult to access experimentally and predict theoretically. This curvature dependence arises from the curvature-dependent molecular structure, which, for small nuclei, can deviate significantly from that of the planar liquid interface. Simulations and density functional theory have been used to predict this curvature dependence, however with contradicting results. Here, we provide the first direct measurement of the curvature-dependent surface tension in nucleating colloidal liquids. We employ critical Casimir forces to finely adjust colloidal particle interactions and induce liquid nucleation, and image individual nuclei at the particle scale to measure their curvature-dependent surface tension directly from thermally excited surface distortions. Using continuum models, we elucidate the interplay between nucleus structure, particle pair potential, and surface tension. Our results reveal a 20% lower surface tension for nuclei of critical size compared to bulk liquids, leading to 3 orders of magnitude higher nucleation rates, thus highlighting the importance of surface tension curvature corrections for accurate prediction of nucleation rates.

Characterization and Applications of Marine Microbial Enzymes in Biotechnology and Probiotics for Animal Health.

Marine microorganisms have been recognized as potential sources of novel enzymes because they are relatively more stable than the corresponding enzymes derived from plants and animals. Enzymes from marine microorganisms also differ from homologous enzymes in terrestrial microorganisms based on salinity, pressure, temperature, and lighting conditions. Marine microbial enzymes can be used in diverse industrial applications. This chapter will focus on the biotechnological applications of marine enzymes and also their use as a tool of marine probiotics to improve host digestion (food digestion, food absorption, and mucus utilization) and cleave molecular signals involved in quorum sensing in pathogens to control disease in aquaculture.

Critical Casimir forces for colloidal assembly.

Critical Casimir forces attract increasing interest due to their opportunities for reversible particle assembly in soft matter and nano science. These forces provide a thermodynamic analogue of the celebrated quantum mechanical Casimir force that arises from the confinement of vacuum fluctuations of the electromagnetic field. In its thermodynamic analogue, solvent fluctuations, confined between suspended particles, give rise to an attractive or repulsive force between the particles. Due to its unique temperature dependence, this effect allows in situ control of reversible assembly. Both the force magnitude and range vary with the solvent correlation length in a universal manner, adjusting with temperature from fractions of the thermal energy, k B T, and nanometre range to several ten kT and micrometer length scale. Combined with recent breakthroughs in the synthesis of complex particles, critical Casimir forces promise the design and assembly of complex colloidal structures, for fundamental studies of equilibrium and out-of-equilibrium phase behaviour. This review highlights recent developments in this evolving field, with special emphasis on the dynamic interaction control to assemble colloidal structures, in and out of equilibrium.

Third type of domain wall in soft magnetic nanostrips.

Magnetic domain walls (DWs) in nanostructures are low-dimensional objects that separate regions with uniform magnetisation. Since they can have different shapes and widths, DWs are an exciting playground for fundamental research, and became in the past years the subject of intense works, mainly focused on controlling, manipulating, and moving their internal magnetic configuration. In nanostrips with in-plane magnetisation, two DWs have been identified: in thin and narrow strips, transverse walls are energetically favored, while in thicker and wider strips vortex walls have lower energy. The associated phase diagram is now well established and often used to predict the low-energy magnetic configuration in a given magnetic nanostructure. However, besides the transverse and vortex walls, we find numerically that another type of wall exists in permalloy nanostrips. This third type of DW is characterised by a three-dimensional, flux closure micromagnetic structure with an unusual length and three internal degrees of freedom. Magnetic imaging on lithographically-patterned permalloy nanostrips confirms these predictions and shows that these DWs can be moved with an external magnetic field of about 1 mT. An extended phase diagram describing the regions of stability of all known types of DWs in permalloy nanostrips is provided.

Elementary depinning processes of magnetic domain walls under fields and currents.

The probability laws associated to domain wall depinning under fields and currents have been studied in NiFe and FePt nanowires. Three basic domain wall depinning processes, associated to different potential landscapes, are found to appear identically in those systems with very different anisotropies. We show that these processes constitute the building blocks of any complex depinning mechanism. A Markovian analysis is proposed, that provides a unified picture of the depinning mechanism and an insight into the pinning potential landscape.

Switchable spin-current source controlled by magnetic domain walls.

Using nonlocal spin injection, spin-orbit coupling, or spincaloritronic effects, the manipulation of pure spin currents in nanostructures underlies the development of new spintronic devices. Here, we demonstrate the possibility to create switchable pure spin current sources, controlled by magnetic domain walls. When the domain wall is located at a given point of the magnetic circuit, a pure spin current is injected into a nonmagnetic wire. Using the reciprocal measurement configuration, we demonstrate that the proposed device can also be used as a pure spin current detector. Thanks to its simple geometry, this device can be easily implemented in spintronics applications; in particular, a single current source can be used both to induce the domain wall motion and to generate the spin signal.

Trichinella infection in wild boars and synanthropic rats in northwest Vietnam.

Trichinellosis is an emerging parasitic zoonosis in North Vietnam. In this survey, hunted and farm-bred wild boars as well as synanthropic rats were sampled in two provinces of northwest Vietnam where outbreaks of trichinellosis have recently occurred. Evidence of Trichinella infection was studied by parasitological, serological and molecular methods. The results showed relatively low prevalence of Trichinella spiralis in hunted wild boars (2/62 (3.2%; 95% CI: 0.8- 4.8)) and rats (23/820 (2.8%; 95% CI: 13.7-32.3)). Parasite burdens in the muscle tissues were between 0.1 and 0.03 larvae/g, and 0.1 and 7 larvae/g in wild boars and rats, respectively. Seroprevalence in farm-bred wild boars was negative. The findings of Trichinella-infected rats in 7 of the 20 districts of Dien Bien and Son La provinces suggest that the parasite is circulating in these regions. These results indicate that the local population and health centers should be made aware of the risks of eating raw or undercooked meat dishes prepared from wild animals.

Controlling colloidal morphologies by critical Casimir forces.

Active control over the assembly of colloidal and nanoparticles has important applications for the design of new nanostructured materials, but it is a difficult task. Here, a new method is presented to control the morphology of colloidal aggregates using critical Casimir forces. Via direct temperature control of critical Casimir forces, the particles are assembled into aggregates with well-defined architecture.

Detection of domain-wall position and magnetization reversal in nanostructures using the magnon contribution to the resistivity.

We show that magnetization reversal detection can be achieved at room temperature using the contribution of magnons to resistivity, in 50 nm wide nanowires with either perpendicular anisotropy (FePt) or in-plane magnetization (NiFe). Even though these nanowires are made from single layers, simple magnetoresistance measurements can be used to measure switching fields, or to detect the position of a domain wall along a nanowire. Surprisingly, in NiFe nanowires, and for applied fields nearly parallel to the wire, the magnon contribution is found to dominate the classical anisotropic magnetoresistance.

Successful AV fistula creation does not lead to higher catheter use: the experience by the Northwest Renal Network 16 Vascular Access Quality Improvement Program. Four years follow-up.

BACKGROUND: In 2002, the Center for Medicare and Medicaid Services (CMS) required all 18 Renal Networks to participate in a Vascular Access Quality Improvement Program (QIP). The Northwest Renal Network (NWRN 16) chose to increase arteriovenous fistula (AVF) use. NWRN 16 hypothesized that strategies which targeted the improvement of AVF rate and the reduction of catheter use were the same. In December 2001, 44.2% of hemodialysis (HD) patients in the NWRN 16 received HD using an AVF which met the Dialysis Outcome Quality Initiative (K/DOQI) 40% AVF guideline for prevalent patients. However, 43% of HD facilities (2869 patients) had less than 40% of AVF and higher HD catheter rates than the average Network catheter rates (25.0 vs. 20.3%). To address the needs of underperforming facilities, NWRN 16 provided education and tools for their vascular access decision makers to promote AVF creation and catheter reduction. METHODS: In 2002, NWRN 16 sponsored four regional workshops targeted at nephrologists, vascular surgeons, HD nurses, and interventional radiologists. RESULTS: Percentage of AVFs in use in invited facilities increased from 31.3% pre-intervention to 56.2% at 4 yrs: 78% increase (99% confidence interval: 77.8% to 81.5%). Percentage of catheters increased from 25% to 25.8%: 3.2% change over 4 yrs (99% confidence interval: 2.5% to 4%). CONCLUSION: The success of Network 16's AVF interventions demonstrates the effectiveness of Network education promoting multidisciplinary teamwork, and innovative strategies to increase dramatically AVF use without substantial increase in catheter use.

Creation of secondary AV fistulas from failed hemodialysis grafts: the role of routine vein mapping.

Pre-existing forearm grafts lead to dilatation of upper arm veins of the ipsilateral arm that greatly facilitates the creation of secondary arteriovenous fistulas (AVF). In this retrospective review of 18 patients, the routine and periodical revision of failed grafts were discontinued. Vein mapping by physical examination or Duplex studies was performed prior to graft failure and a secondary AVF was created when the graft failed. Using this management strategy, an AVF creation success rate of 95% was achieved despite high incidence of co-morbidity factors within the patient population. This success rate demonstrates the value of vein selection by vascular mapping prior to graft failure and early vascular access planning in the successful creation of secondary AVF.

Successful multidisciplinary interventions for arterio-venous fistula creation by the Pacific Northwest Renal Network 16 vascular access quality improvement program.

BACKGROUND: In December 2001, 44.2% of hemodialysis (HD) patients in the Northwest Renal Network (NWRN 16) received dialysis using an arteriovenous fistula (AVF). Substantial differences were noted in percentages of patients with AVF, ranging from 5% to 90% of the facility population, suggesting wide variation in physician practice patterns within the Network. To address the needs of facilities having < 40% AVF, NWRN 16 provided education and tools for their vascular access decision-makers to promote AVF creation. METHODS: In 2002, the Network sponsored 4 regional workshops targeted to nephrologists, vascular surgeons, dialysis nurses, and interventional radiologists. RESULTS: 46 facilities (43% of all Network facilities) had <40% AVF in use in December, 2001, dialyzing 2940 patients (Invited Units). Percent AVF in use in all the Invited Facilities increased from 31.3% pre-intervention to 39.8% at 1 year (p<0.001 vs pre) to 56.2% at four years: 79.8% increase in the prevalent AVF rate over a four-year period (95% confidence interval: 77.8% to 81.7%). CONCLUSION: Low prevalent AVF rates in many NWRN 16 facilities may have resulted from differences in physician practice patterns. The success of Network 16 AVF Intervention demonstrates the effectiveness of Network education promoting multidisciplinary teamwork, innovative strategies to increase AVF rates among dialysis patients.

Modulation of the multisubstrate specificity of Thermus maltogenic amylase by truncation of the N-terminal domain and by a salt-induced shift of the monomer/dimer equilibrium.

The relation between the quaternary structure and the substrate specificity of Thermus maltogenic amylase (ThMA) has been investigated. Sedimentation diffusion equilibrium ultracentrifugation and gel filtration analyses, in combination with the crystal structure determined recently, have demonstrated that ThMA existed in a monomer/dimer equilibrium. The truncation of ThMA by removing the N-terminal domain, which is composed of 124 amino acid residues, resulted in the complete monomerization of the enzyme (ThMADelta124) accompanied by a drastic decrease in the activity for beta-cyclodextrin (beta-CD) and a relatively smaller reduction of the activity for starch. Despite the overall low activity of ThMADelta124, the activity was higher toward starch than beta-CD, and the ratio of the specific activities toward these substrates was approximately 100 fold higher than that of wild-type ThMA. Furthermore, the addition of KCl to wild-type ThMA shifted the monomer/dimer equilibrium toward the monomer. In the presence of 1.0 M KCl, the relative activity of ThMA toward beta-CD decreased to 74%, while that for soluble starch increased to 194% compared to the activities in the absence of KCl. Thus, the ThMA monomer and dimer are both inferred to be enzymatically active but with a somewhat different substrate preference. Kinetic parameters of the wild-type and truncated enzymes also are in accordance with the changes in their specific activities. We thus provide evidence in support of a model, which shows that the relative multisubstrate specificity of ThMA is influenced by the monomer/dimer equilibrium of the enzyme.

A high-resolution reference map for cytoplasmic and membrane-associated proteins of Corynebacterium glutamicum.

We present a high-resolution reference map for soluble proteins obtained from Corynebacterium glutamicum cells grown in glucose minimal medium. The analysis window covers the pl range from 4-6 and the molecular mass range from 5-100 kDa. Using overlapping narrow immobilized pH gradients for isoelectric focusing, 970 protein spots were detected after second-dimensional separation on SDS-polyacrylamide gels and colloidal Coomassie-staining. By tryptic peptide mass fingerprinting 169 protein spots were identified, representing 152 different proteins including many enzymes involved in central metabolism (18), amino acid biosynthesis (24) and nucleotide biosynthesis (11). Thirty-five of the identified proteins have no known function. A comparison of the observed and the expected physicochemical properties of the identified proteins indicated that nine proteins were covalently modified, since variants with apparently identical molecular mass, but differing pl were detected. The N-termini of eight proteins were determined by post-source decay (PSD) analysis of selected peptides. In addition to the soluble proteins, a map of the membrane-bound proteins within the pl range 4-7 is presented, which contains 660 protein spots, 22 of which were identified, representing 13 different proteins.

[Hepatectomy in intrahepatic lithiasis]. / Hépatectomie dans la lithiase intrahépatique.

STUDY AIM: The aim of this study was to report the immediate results of a series of 65 hepatic resections for hepatolithiasis performed in Vietnam. PATIENTS AND METHOD: From 1986 to 1998, 44 men and 21 women (mean age: 40 years) underwent hepatic resection for hepatolithiasis. Fourty patients had previously undergone one or several operations for hepatolithiasis. The procedure was performed on emergency in 25 patients. Indications for hepatic resection were: angiocholitis and liver abscess in 22 cases, stones closely inserted in the biliary duct in 20 cases, hemobilia in 12 cases, stones located above a biliary stricture in 8 cases and stones associated with a postoperative biliary fistula in 3 cases. Liver resections (minor in 61 patients, including 55 left lobectomies, and major in 4 patients) were performed through transhepatic approach according to the Ton That Tung technique and followed by an external biliary drainage with a Kehr tube. RESULTS: There were 6 postoperative deaths (9%), 3 due to septic shock, 2 to cachexia, and 1 to liver failure. The 15 patients with complications recovered with conservative therapy. Bile infection was present in 93%, mostly with Escherichia coli and Enterobacter. Pigmented stones were usually found. CONCLUSION: Vietnam is a country with high incidence of hepatolithlasis. Hepatic resection is an adequate treatment for localized intrahepatic bile duct stones when the involved segment including biliary strictures and calculi can be completely removed. The procedure may be performed on emergency for liver abscess, or hemobilia.

Symptoms associated with oophorectomy and tamoxifen treatment for breast cancer in premenopausal Vietnamese women.

There are very few data about the efficacy and toxicity of adjuvant systemic therapies for breast cancer in non-western populations. In 1993 in Vietnam we began a randomized controlled clinical trial on premenopausal women with operable breast cancer comparing adjuvant surgical oophorectomy plus tamoxifen with observation and this same combined hormonal treatment on recurrence. We evaluated the symptoms reported at regular follow-up visits by the first 482 premenopausal women entered in this clinical trial and treated with surgical oophorectomy plus tamoxifen or observation. Hot flash frequency and intensity, vaginal discharge, and genital pruritus were the only symptoms to occur more frequently in oophorectomy and tamoxifen-treated subjects. Seventy-seven percent of oophorectomy/tamoxifen subjects reported grade 1 or more and 44% grade 2 or more hot flash frequency symptoms in the first 12 months, versus 9% and 1% of observation subjects, respectively. Twenty percent of oophorectomy/tamoxifen subjects had grade 2 or greater intensity of hot flashes some time in the first 12 months versus 0% in observation subjects. Through three years, vasomotor symptoms were reported more frequently in oophorectomy/tamoxifen-treated women (in 23% vs. 3% at three years, mostly grade 1 toxicities). While noted and persistent vasomotor symptoms were found with oophorectomy plus tamoxifen in this population of Vietnamese women, these were of lower grades and tolerable. This adjuvant treatment may be widely accepted if it is demonstrated to be effective in this population.

The use of a water extract from the bark of Choerospondias axillaris in the treatment of second degree burns.

Burns are common in Vietnam, and because of economic constraints and limited resources for the import of appropriate treatments, the health authorities are obliged to rely on traditional herbal remedies. It is therefore essential to evaluate current drugs, one of which is the water extract of the bark of the tree Choerospondias axillaris. It has been used for many years in the Vietnam-Sweden hospital at Uong Bi in northern Vietnam. We assessed the efficacy of the remedy in an open, randomised controlled clinical trial, in which 20 patients with second degree burns were treated with the extract of the Choerospondias axillaris and 19 with saline gauze. The mean healing time was significantly shorter for patients treated with Choerospondias axillaris (11 days) compared with patients treated with saline gauze (17 days) (p < 0.01), and the number of wound infections was significantly lower in the Choerospondias axillaris group (7/20 compared with 16/19, p = 0.003). The bark extract was easy to apply and additional wound care was not usually necessary, while the treatment with saline gauze was laborious for both patients and staff and was much more expensive. The extract from Choerospondias axillaris is a convenient treatment for second degree burns in both children and adults.

Ion Chromatographic determination of trace anions and cations in high-purity water.

An ion chromatographic measuring system for the off-line and on-line determination of some trace anions and cations in high-purity water is presented. The ng/L level of anions and cations in 20-130 mL high-purity water can be analyzed after preconcentration on ion exchange columns. The concentrated solutes are eluted by eluents from the trap column and separated using a Dionex analytical column. The quantification of each ion is achieved using the suppressor technique and conductivity detector. The influence of various parameters on the results is discussed. The detection limits of cations and anions are between 10 and 30 ng/L for chloride, bromide, nitrate, phosphate, sulphate, sodium, ammonium, potassium, magnesium and calcium ions.