Effect of CoFe dusting layer and annealing on the magnetic properties of sputtered Ta/W/CoFeB/CoFe/MgO layer structures.

We explored the effect of a CoFe wedge inserted as a dusting layer (0.2 nm-0.4 nm thick) at the CoFeB/MgO interface of a sputtered Ta(2 nm)/W(3 nm)/CoFeB(0.9 nm)/MgO(3 nm)/Ta(2 nm) film-a typical structure for spin-orbit torque devices. Films were annealed at temperatures varying between 300 °C and 400 °C in an argon environment. Ferromagnetic resonance studies and vibrating sample magnetometry measurements were carried out to estimate the effective anisotropy field, the Gilbert damping, the saturation magnetization and the dead layer thickness as a function of the CoFe thickness and across several annealing temperatures. While the as-deposited films present only easy-plane anisotropy, a transition along the wedge from in-plane to out-of-plane was observed across several annealing temperatures, with evidence of a spin-reorientation transition separating the two regions.

A room-temperature semiconductor spaser operating near 1.5 µm.

Room temperature spasing of surface plasmon polaritons at 1.46 µm wavelength has been demonstrated by sandwiching a gold-film plasmonic waveguide between optically pumped InGaAs quantum-well gain media. The spaser exhibits gain narrowing, the expected transverse-magnetic polarization, and mirror feedback provided by cleaved facets in a 1-mm long cavity fabricated with a flip-chip approach. The 1.06-µm pump-threshold of ~60 kW/cm2 is in good agreement with calculations. The architecture is readily adaptable to all-electrical operation on an integrated microchip.

An integrated surface-plasmon source.

A compact and versatile source of coherent surface-plasmon polaritions (SPPs) is demonstrated by end-coupling a laser diode operating at 1.46 microm to a plasmonic waveguide integrated on the same microchip. With an optimized overlap between the spatial-modes of the laser and a planar-stripe waveguide, a high coupling efficiency of approximately 36% is achieved, that computations show could approach approximately 60% with smaller, readily achievable gaps between laser and waveguide. This integrated and electrically-activated source, with an available SPP power limited only by the laser diode, appears ideally suited for directly driving plasmonic circuitry or surface-enhanced sensors.

Magnetoelastic Effects in Doubly Clamped Electroplated Co77Fe23 Microbeam Resonators.

Magnetostrictive Co77Fe23 films are fully suspended to produce free-standing, clamped-clamped, microbeam resonators. A negative or positive shift in the resonant frequency is observed for magnetic fields applied parallel or perpendicular to the length of the beam, respectively, confirming the magnetoelastic nature of the shift. Notably, the resonance shifts linearly with higher-bias fields oriented perpendicular to the beam's length. Domain imaging elucidates the distinction in the reversal processes along the easy and hard axes. Together, these results suggest that through modification of the magnetic anisotropy, the frequency shift and angular dependence can be tuned, producing highly magnetic-field-sensitive resonators.

Disordered RuO2 exhibits two dimensional, low-mobility transport and a metal-insulator transition.

The discovery of low-dimensional metallic systems such as high-mobility metal oxide field-effect transistors, the cuprate superconductors, and conducting oxide interfaces (e.g., LaAlO3/SrTiO3) has stimulated research into the nature of electronic transport in two-dimensional systems given that the seminal theory for transport in disordered metals predicts that the metallic state cannot exist in two dimensions (2D). In this report, we demonstrate the existence of a metal-insulator transition (MIT) in highly disordered RuO2 nanoskins with carrier concentrations that are one-to-six orders of magnitude higher and with mobilities that are one-to-six orders of magnitude lower than those reported previously for 2D oxides. The presence of an MIT and the accompanying atypical electronic characteristics place this form of the oxide in a highly diffusive, strong disorder regime and establishes the existence of a metallic state in 2D that is analogous to the three-dimensional case.

Guided resonances in asymmetrical GaN photonic crystal slabs observed in the visible spectrum.

We demonstrate that guided resonant modes can be readily observed in asymmetrical photonic crystal slabs on high-index substrates. In spite of the high radiative loss associated with all optical modes in these cases, the guided resonant modes are found to give rise to strong high-Q features in the transmission spectra. Since these photonic crystal structures are far more robust and easier to fabricate than the free-standing photonic crystal membranes used in previous studies of guided resonant modes, detailed studies of relevant optical phenomena and the implementation of proposed applications are greatly simplified.

Re-expression of p75NTR by adult motor neurons after axotomy is triggered by retrograde transport of a positive signal from axons regrowing through damaged or denervated peripheral nerve tissue.

To investigate different types of potential signalling mechanisms that regulate neuronal reactions to axotomizing injury, we compared the re-expression of the low-affinity neurotrophin receptor, p75NTR, and the down-regulation of choline acetyltransferase expression, after various combinations of axotomy, crush injury and blockade of axonal transport in adult hypoglossal motor neurons in the rat. We found that pure axotomy in the absence of crush injury down-regulated choline acetyltransferase, but did not induce p75NTR re-expression. Blockade of axonal transport with colchicine had an identical effect. In contrast, both a crush injury on its own, or a crush injury proximal to a complete axotomy, induced p75NTR re-expression and down-regulated expression of choline acetyltransferase. Blockade of axonal transport with colchicine or tight ligation proximal to a crush prevented the crush injury-induced re-expression of p75NTR. Infusion of vehicle, nerve growth factor or ciliary neurotrophic factor induced low levels of p75NTR re-expression that were not significantly different from each other and were substantially lower than crush-induced levels. These findings confirm previous suggestions that the loss of choline acetyltransferase expression is due to the interruption of a constitutive retrograde signal, and show that the re-expression of p75NTR by adult motor neurons after axotomy is triggered by the retrograde transport of a positive signal derived from axons that are regrowing through damaged or denervated peripheral nerve tissue. The precise source and nature of this signal are not yet clear.

Injury-resistant retinal ganglion cells that are rich in cytochrome oxidase.

Previous studies have demonstrated that the vast majority of retinal ganglion cells (RGCs) die one month after optic nerve transection. However, a small percentage do not degenerate. The present study examined one aspect of the chemical nature of these surviving RGCs using cytochrome oxidase (CO) as a neuronal marker in whole-mounted retinae. In the normal retina, 4.3% of the total population of RGCs show high CO activity. One month after optic nerve transection, 37% of the CO-positive RGCs counted in the control retinae survive and, because they stain with CO, must be metabolically active. Previous studies have shown that only up to 10% of the total RGC population survive optic nerve transection. The implication of our results is that the CO-positive RGCs, as a subpopulation, are more resistant to injury than the general population of RGCs.

Protein gene product 9.5-immunoreactive retinal neurons in normal developing rats and rats with optic nerve or tract lesion.

The present immunocytochemical study indicates that protein gene product 9.5 (PGP 9.5) in the rat retina first appears in a population of neurons in the inner and central part of the neuroblast layer at embryonic day (E) 14. Presumptive horizontal cells which are PGP 9.5 positive were observed at E17. At birth, cells in the inner nuclear layer and ganglion cell layer (GCL) as well as the inner plexiform layer (IPL) were positive. Further differentiation, particularly the appearance and the formation of immunoreactive sublaminae in the IPL, was observed in the first 2 postnatal weeks. This pattern reached adult levels by postnatal day 14. In rats with unilateral neonatal optic tract lesion or optic nerve transection as young adults, 43-45% of the immunoreactive cells were lost in the GCL. However, only minor changes were detected in the IPL, suggesting that amacrine cells contribute mainly to the PGP 9.5 immunoreactivity in this laminar zone of the retina.

Laser photocoagulation alters the pattern of staining for neurotrophin-4, GFAP, and CD68 in human retina.

AIMS: To investigate the staining pattern of neurotrophin-3 (NT3), neurotrophin-4 (NT4), and brain derived neurotrophic factor (BDNF) as well as glial fibrillary acid protein (GFAP) and CD68 in lasered human retina. METHODS: Retinal laser photocoagulation was performed on four patients (two males, two females) with choroidal malignant melanoma 1-6 days before enucleation. Three other enucleated eyes with malignant melanoma and three normal cadaveric donor eyes were used as controls. Immunohistochemistry was performed to investigate the pattern of staining of NT3, NT4, BDNF, GFAP, and CD68 in 7 mm sections of fixed specimens. RESULTS: Expression of NT4 was detected in the inner and outer nuclear layers of all the retinal sections examined but no NT3 and BDNF staining was seen. NT4 staining was found to be less intense in lasered and melanoma controls compared to normal cadaveric donor retinas. There was an upregulation of GFAP expression in both lasered and control eyes with melanoma in comparison with normal controls. CD68 staining was only observed in retinal pigment epithelium and choroid of lasered eyes. CONCLUSION: NT4 is expressed in inner and outer nuclear layers of normal human retina and its expression is downregulated following laser photocoagulation. This occurs in parallel with an increased expression of GFAP suggesting that reactive changes in Muller cells may be responsible for reduced NT4 staining. Expression of CD68 at the site of laser injury is consistent with a wound healing process as a response to local damage.

Decreased numerical density of kainate receptor-positive neurons in the orbitofrontal cortex of chronic schizophrenics.

We utilised postmortem brain tissue to quantify sections of left and right orbitofrontal cortex (area 11) from nine schizophrenic and eight control patients from the Charing Cross Prospective Schizophrenia Study immunostained for the presence of the kainate receptor (GluR5/6/7). The numerical density of neurons immunopositive for kainate receptor was measured. Other sections from the same blocks were stained with cresyl violet to determine the total neuronal numerical density. All measurements were made blind: diagnoses were only revealed by a third party after measurements were completed. There was a significant reduction (21%) in numerical density of kainate receptor-positive neurons in both cortices in the schizophrenic group (488 cells/mm2) compared to that in the control group (618 cells/mm2) (P=0.033). Nissl-stained tissue showed no significant difference in total neuronal numerical density between control and schizophrenic groups. These observations suggest that there are actually fewer kainate receptor-positive neurons in schizophrenic orbitofrontal cortex. There was no correlation of reduced kainate receptor-positive cell number with age at death, postmortem interval, or other possibly confounding neuropathology. Our results support the concept of there being reduced glutamatergic activity in frontal cortex in schizophrenia.

Cell-free synthesis of proteins related to sn-glycerol-3-phosphate transport in Escherichia coli.

An Escherichia coli periplasmic protein (GlpT) related to sn-glycerol-3-phosphate transport was synthesized in a cell-free system directed by hybrid plasmic ColE1-glpT DNA. The in vitro product cross-reacted with antisera against the purified protein. The ColE1-glpT DNA-directed cell-free system was induced by sn-glycerol-3-phosphate and phosphonomycin and was dependent on cyclic AMP. The in vitro-synthesized protein showed the characteristics of a multimeric protein, as did the purified periplasmic protein. The main proportion of the newly synthesized product had a higher molecular weight than the mature protein found in the periplasm of cells and showed a more positive charge in two-dimensional gel electrophoresis. Thus, a proportion of this protein is presumed to be synthesized in vitro as a precursor. The cell-free system yielded a second protein that is likely to be also coded for by the glpT operon. This protein had a molecular weight of approximately 33,000 in sodium dodecyl sulfate-acrylamide gel electrophoresis and behaved like an intrinsic membrane protein.

Plasma exchanges in frequently recurrent hemolytic-uremic syndrome in a child.

22 plasma exchanges (PE) were carried out on a 9 year old boy with frequently recurrent hemolytic-uremic syndrome (HUS) and persistently low plasma factor which normally stimulates vascular prostacyclin (PGI2) release. The factor was partially restored after PE but declined within 2-4 weeks. No major recurrence of HUS occurred, but "minor" attacks recurred despite PE. It is likely that a genetic predisposition is responsible for the recurrences of HUS, but the ultimate relationship between recurrent HUS and persistent plasma deficiency for PGI2-release remains to be defined.

Functional analysis of the adsorption protein of two filamentous phages with different host specificities.

The gene 3 coding for one minor coat protein (adsorption protein) of phage IKe was cloned into an expression plasmid and overproduced. The presence of a promoter for this gene could be demonstrated as well as the incorporation of the IKe gene 3 protein (g3p) into the cytoplasmic membrane of host cells. When 110 carboxy-terminal amino acids were deleted, the truncated protein was translocated across the cytoplasmic membrane into the periplasm. Thus the deleted amino acids bear a membrane anchor domain. In contrast to the partly homologous g3p of the Ff phages, IKe g3p did not alter the membrane properties of its host. IKe g3p was not incorporated into Ff phage particles in amounts detectable by our assays although the presence of IKe g3p may affect the efficiency of Ff phage production. The existence of a structural feature necessary for the specific recognition of the respective g3p during phage assembly is deduced.

Plasmapheresis as a therapeutic measure in hemolytic-uremic syndrome in children.

Three children with hemolytic-uremic syndrome (HUS) were successfully treated with plasmapheresis (HUS) were successfully treated with plasmapheresis (PP) combined with early hemodialysis and administration of Aspirin and dipyridamole. Stimulation of vascular prostacyclin release with patients' plasma was measured before and after PP. It was reduced before and increased after plasma exchange. The data indicate that PP might be a useful tool in treatment of (HUS) in children.

A genomic DNA segment from Petunia hybrida leads to increased transformation frequencies and simple integration patterns.

A 2-kilobase (kb) genomic fragment was selected from Petunia hybrida that increased transformation efficiencies by at least a factor of 20 after direct DNA transfer to petunia and tobacco protoplasts when supercoiled plasmid DNA was used. Because of this effect this fragment was named transformation booster sequence (TBS). Increased transformation frequencies were observed for plasmids that contained either the 2-kb fragment in dimeric or monomeric form or an internal 1.1-kb fragment of TBS. Analysis of transformants revealed that preferentially one copy of foreign DNA is integrated. Thus, TBS improves the poor transformation frequencies of direct gene transfer using circular plasmids, while it conserves the simple integration pattern that is important for practical applications. Possible mechanisms of TBS action are discussed.

Increased expression of NADPH-diaphorase in visual centres after unilateral optic nerve transection in the rat.

The present study shows an increase NADPH-d histochemical staining in the optic layers of the superior colliculus, the ventral nucleus of the lateral geniculate body and the primary visual cortex in the rat after transection of the contralateral optic nerve. The alteration was observed 4-60 days after the lesion, with a maximum at 30 days. These results suggest that retinal activity has a transneuronal and time-dependent regulatory effect on nitric oxide synthesis in denervated or visually deprived visual centres, an increase that may play a role in enhancing local blood flow and could be neuroprotective in function.