Spin-Momentum Locking and Ultrafast Spin-Charge Conversion in Ultrathin Epitaxial Bi1 - x Sbx Topological Insulator

The helicity of three-dimensional (3D) topological insulator surface states has drawn significant attention in spintronics owing to spin-momentum locking where the carriers' spin is oriented perpendicular to their momentum. This property can provide an efficient method to convert charge currents into spin currents, and vice-versa, through the Rashba-Edelstein effect. However, experimental signatures of these surface states to the spin-charge conversion are extremely difficult to disentangle from bulk state contributions. Here, spin- and angle-resolved photo-emission spectroscopy, and time-resolved THz emission spectroscopy are combined to categorically demonstrate that spin-charge conversion arises mainly from the surface state in Bi_{1 - x} Sb_x ultrathin films, down to few nanometers where confinement effects emerge. This large conversion efficiency is correlated, typically at the level of the bulk spin Hall effect from heavy metals, to the complex Fermi surface obtained from theoretical calculations of the inverse Rashba-Edelstein response. Both surface state robustness and sizeable conversion efficiency in epitaxial Bi_{1 - x} Sb_x thin films bring new perspectives for ultra-low power magnetic random-access memories and broadband THz generation.

Automating Quantitative Measures of an Established Conventional MRI Scoring System for Preterm-Born Infants Scanned between 29 and 47 Weeks' Postmenstrual Age

BACKGROUND AND PURPOSE

Conventional MR imaging scoring is a valuable tool for risk stratification and prognostication of outcomes, but manual scoring is time-consuming, operator-dependent, and requires high-level expertise. This study aimed to automate the regional measurements of an established brain MR imaging scoring system for preterm neonates scanned between 29 and 47 weeks' postmenstrual age.

MATERIALS AND METHODS

This study used T2WI from the longitudinal Prediction of PREterm Motor Outcomes cohort study and the developing Human Connectome Project. Measures of biparietal width, interhemispheric distance, callosal thickness, transcerebellar diameter, lateral ventricular diameter, and deep gray matter area were extracted manually (Prediction of PREterm Motor Outcomes study only) and automatically. Scans with poor quality, failure of automated analysis, or severe pathology were excluded. Agreement, reliability, and associations between manual and automated measures were assessed and compared against statistics for manual measures. Associations between measures with postmenstrual age, gestational age at birth, and birth weight were examined (Pearson correlation) in both cohorts.

RESULTS

A total of 652 MRIs (86%) were suitable for analysis. Automated measures showed good-to-excellent agreement and good reliability with manual measures, except for interhemispheric distance at early MR imaging (scanned between 29 and 35 weeks, postmenstrual age; in line with poor manual reliability) and callosal thickness measures. All measures were positively associated with postmenstrual age (r = 0.11-0.94; R² = 0.01-0.89). Negative and positive associations were found with gestational age at birth (r = -0.26-0.71; R² = 0.05-0.52) and birth weight (r = -0.25-0.75; R² = 0.06-0.56). Automated measures were successfully extracted for 80%-99% of suitable scans.

CONCLUSIONS

Measures of brain injury and impaired brain growth can be automatically extracted from neonatal MR imaging, which could assist with clinical reporting.

Collaboration between a tertiary pain centre and community teams during the pandemic

People with chronic pain faced potential treatment disruption during the COVID-19 pandemic in Singapore, as the focus of healthcare shifted. A model of rapid integration of a pain centre with community healthcare teams was implemented to care for vulnerable older patients with chronic pain and multiple comorbidities. Telemedicine and home visits by community nurses were used, with risk-mitigation measures, ensuring comprehensive assessment and treatment compliance. Medications from pain physicians were delivered at home through a hospital pharmacy. A secure national electronic health records system used by all teams ensured seamless access and documentation. Potential emergency department visits, admissions and delayed discharges were thus avoided. Integration of community teams with chronic pain management services can be recommended to ensure pandemic preparedness.

Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111)

Relating magnetotransport properties to specific spin textures at surfaces or interfaces is an intense field of research nowadays. Here, we investigate the variation of the electrical resistance of Ge(111) grown epitaxially on semi-insulating Si(111) under the application of an external magnetic field. We find a magnetoresistance term that is linear in current density j and magnetic field B, hence, odd in j and B, corresponding to a unidirectional magnetoresistance. At 15 K, for I=10  μA (or j=0.33  A m^{-1}) and B=1  T, it represents 0.5% of the zero field resistance, a much higher value compared to previous reports on unidirectional magnetoresistance (UMR). We ascribe the origin of this magnetoresistance to the interplay between the externally applied magnetic field and the pseudomagnetic field generated by the current applied in the spin-splitted subsurface states of Ge(111). This unidirectional magnetoresistance is independent of the current direction with respect to the Ge crystal axes. It progressively vanishes, either using a negative gate voltage due to carrier activation into the bulk (without spin-splitted bands), or by increasing the temperature due to the Rashba energy splitting of the subsurface states lower than ∼58k_{B}. We believe that UMR could be used as a powerful probe of the spin-orbit interaction in a wide range of materials.

Validation of an MRI Brain Injury and Growth Scoring System in Very Preterm Infants Scanned at 29- to 35-Week Postmenstrual Age

BACKGROUND AND PURPOSE

The diagnostic and prognostic potential of brain MR imaging before term-equivalent age is limited until valid MR imaging scoring systems are available. This study aimed to validate an MR imaging scoring system of brain injury and impaired growth for use at 29 to 35 weeks postmenstrual age in infants born at <31 weeks gestational age.

MATERIALS AND METHODS

Eighty-three infants in a prospective cohort study underwent early 3T MR imaging between 29 and 35 weeks' postmenstrual age (mean, 32⁺² ± 1⁺³ weeks; 49 males, born at median gestation of 28⁺⁴ weeks; range, 23⁺⁶-30⁺⁶ weeks; mean birthweight, 1068 ± 312 g). Seventy-seven infants had a second MR scan at term-equivalent age (mean, 40⁺⁶ ± 1⁺³ weeks). Structural images were scored using a modified scoring system which generated WM, cortical gray matter, deep gray matter, cerebellar, and global scores. Outcome at 12-months corrected age (mean, 12 months 4 days ± 1⁺² weeks) consisted of the Bayley Scales of Infant and Toddler Development, 3rd ed. (Bayley III), and the Neuro-Sensory Motor Developmental Assessment.

RESULTS

Early MR imaging global, WM, and deep gray matter scores were negatively associated with Bayley III motor (regression coefficient for global score β = -1.31; 95% CI, -2.39 to -0.23; P = .02), cognitive (β = -1.52; 95% CI, -2.39 to -0.65; P < .01) and the Neuro-Sensory Motor Developmental Assessment outcomes (β = -1.73; 95% CI, -3.19 to -0.28; P = .02). Early MR imaging cerebellar scores were negatively associated with the Neuro-Sensory Motor Developmental Assessment (β = -5.99; 95% CI, -11.82 to -0.16; P = .04). Results were reconfirmed at term-equivalent-age MR imaging.

CONCLUSIONS

This clinically accessible MR imaging scoring system is valid for use at 29 to 35 weeks postmenstrual age in infants born very preterm. It enables identification of infants at risk of adverse outcomes before the current standard of term-equivalent age.

Evidence for spin-to-charge conversion by Rashba coupling in metallic states at the Fe/Ge(111) interface

The spin-orbit coupling relating the electron spin and momentum allows for spin generation, detection and manipulation. It thus fulfils the three basic functions of the spin field-effect transistor. However, the spin Hall effect in bulk germanium is too weak to produce spin currents, whereas large Rashba effect at Ge(111) surfaces covered with heavy metals could generate spin-polarized currents. The Rashba spin splitting can actually be as large as hundreds of meV. Here we show a giant spin-to-charge conversion in metallic states at the Fe/Ge(111) interface due to the Rashba coupling. We generate very large charge currents by direct spin pumping into the interface states from 20 K to room temperature. The presence of these metallic states at the Fe/Ge(111) interface is demonstrated by first-principles electronic structure calculations. By this, we demonstrate how to take advantage of the spin-orbit coupling for the development of the spin field-effect transistor.

Highly efficient and tunable spin-to-charge conversion through Rashba coupling at oxide interfaces

The spin-orbit interaction couples the electrons' motion to their spin. As a result, a charge current running through a material with strong spin-orbit coupling generates a transverse spin current (spin Hall effect, SHE) and vice versa (inverse spin Hall effect, ISHE). The emergence of SHE and ISHE as charge-to-spin interconversion mechanisms offers a variety of novel spintronic functionalities and devices, some of which do not require any ferromagnetic material. However, the interconversion efficiency of SHE and ISHE (spin Hall angle) is a bulk property that rarely exceeds ten percent, and does not take advantage of interfacial and low-dimensional effects otherwise ubiquitous in spintronic hetero- and mesostructures. Here, we make use of an interface-driven spin-orbit coupling mechanism-the Rashba effect-in the oxide two-dimensional electron system (2DES) LaAlO₃/SrTiO₃ to achieve spin-to-charge conversion with unprecedented efficiency. Through spin pumping, we inject a spin current from a NiFe film into the oxide 2DES and detect the resulting charge current, which can be strongly modulated by a gate voltage. We discuss the amplitude of the effect and its gate dependence on the basis of the electronic structure of the 2DES and highlight the importance of a long scattering time to achieve efficient spin-to-charge interconversion.

Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature

Facing the ever-growing demand for data storage will most probably require a new paradigm. Nanoscale magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films in which the cobalt layer is sandwiched between two heavy metals and so provides additive interfacial Dzyaloshinskii-Moriya interactions (DMIs), which reach a value close to 2 mJ m(-2) in the case of the Ir|Co|Pt asymmetric multilayers. Using a magnetization-sensitive scanning X-ray transmission microscopy technique, we imaged small magnetic domains at very low fields in these multilayers. The study of their behaviour in a perpendicular magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the large DMI. This discovery of stable sub-100 nm individual skyrmions at room temperature in a technologically relevant material opens the way for device applications in the near future.

Spin transport in p-type germanium

We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle θ(SHE) in Ge-p (6-7 x 10(-4) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering.

Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator: α-Sn Films

We present results on spin to charge current conversion in experiments of resonant spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) α-Sn. By angle-resolved photoelectron spectroscopy (ARPES), we first check that the Dirac cone (DC) at the α-Sn (0 0 1) surface subsists after covering Sn with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into α-Sn layers induces a lateral charge current that can be ascribed to the inverse Edelstein effect by the DC states. Our observation of an inverse Edelstein effect length much longer than those generally found for Rashba interfaces demonstrates the potential of TIs for the conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of the TI for spin to charge conversion and the conditions to reach it.

Spin pumping and inverse spin Hall effect in platinum: the essential role of spin-memory loss at metallic interfaces

Through combined ferromagnetic resonance, spin pumping, and inverse spin Hall effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate consistent values of ℓsfPt=3.4±0.4  nm and θSHEPt=0.056±0.010 for the respective spin diffusion length and spin Hall angle for Pt. Our data and model emphasize the partial depolarization of the spin current at each interface due to spin-memory loss. Our model reconciles the previously published spin Hall angle values and explains the different scaling lengths for the ferromagnetic damping and the spin Hall effect induced voltage.

Towards electrical spin injection into LaAlO3-SrTiO3

Future spintronics devices will be built from elemental blocks allowing the electrical injection, propagation, manipulation and detection of spin-based information. Owing to their remarkable multi-functional and strongly correlated character, oxide materials already provide such building blocks for charge-based devices such as ferroelectric field-effect transistors (FETs), as well as for spin-based two-terminal devices such as magnetic tunnel junctions, with giant responses in both cases. Until now, the lack of suitable channel materials and the uncertainty of spin-injection conditions in these compounds had however prevented the exploration of similar giant responses in oxide-based lateral spin transport structures. In this paper, we discuss the potential of oxide-based spin FETs and report magnetotransport data that suggest electrical spin injection into the LaAlO(3)-SrTiO(3) interface system. In a local, three-terminal measurement scheme, we analyse the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or longitudinal magnetic fields (Hanle and 'inverted' Hanle effects). The spin accumulation signal appears to be much larger than expected, probably owing to amplification effects by resonant tunnelling through localized states in the LaAlO(3). We give perspectives on how to achieve direct spin injection with increased detection efficiency, as well on the implementation of efficient top gating schemes for spin manipulation.

Crossover from spin accumulation into interface states to spin injection in the germanium conduction band

Electrical spin injection into semiconductors paves the way for exploring new phenomena in the area of spin physics and new generations of spintronic devices. However the exact role of interface states in the spin injection mechanism from a magnetic tunnel junction into a semiconductor is still under debate. In this Letter, we demonstrate a clear transition from spin accumulation into interface states to spin injection in the conduction band of n-Ge. We observe spin signal amplification at low temperature due to spin accumulation into interface states followed by a clear transition towards spin injection in the conduction band from 200 K up to room temperature. In this regime, the spin signal is reduced to a value compatible with the spin diffusion model. More interestingly, the observation in this regime of inverse spin Hall effect in germanium generated by spin pumping and the modulation of the spin signal by a gate voltage clearly demonstrate spin accumulation in the germanium conduction band.

Gate-controlled spin injection at LaAlO3/SrTiO3 interfaces

We report results of electrical spin injection at the high-mobility quasi-two-dimensional electron system (2-DES) that forms at the LaAlO3/SrTiO3 interface. In a nonlocal, three-terminal measurement geometry, we analyze the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or transverse magnetic fields (Hanle and inverted Hanle effect). The influence of bias and back-gate voltages reveals that the spin accumulation signal is amplified by resonant tunneling through localized states in the LaAlO3 strongly coupled to the 2-DES by tunneling transfer.

Evidence-based guideline: Antiepileptic drug selection for people with HIV/AIDS: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Ad Hoc Task Force of the Commission on Therapeutic Strategies of the International League Against Epilepsy

OBJECTIVE

To develop guidelines for selection of antiepileptic drugs (AEDs) among people with HIV/AIDS.

METHODS

The literature was systematically reviewed to assess the global burden of relevant comorbid entities, to determine the number of patients who potentially utilize AEDs and antiretroviral agents (ARVs), and to address AED-ARV interactions.

RESULTS AND RECOMMENDATIONS

AED-ARV administration may be indicated in up to 55% of people taking ARVs. Patients receiving phenytoin may require a lopinavir/ritonavir dosage increase of ~50% to maintain unchanged serum concentrations (Level C). Patients receiving valproic acid may require a zidovudine dosage reduction to maintain unchanged serum zidovudine concentrations (Level C). Coadministration of valproic acid and efavirenz may not require efavirenz dosage adjustment (Level C). Patients receiving ritonavir/atazanavir may require a lamotrigine dosage increase of ∼50% to maintain unchanged lamotrigine serum concentrations (Level C). Coadministration of raltegravir/atazanavir and lamotrigine may not require lamotrigine dosage adjustment (Level C). Coadministration of raltegravir and midazolam may not require midazolam dosage adjustment (Level C). Patients may be counseled that it is unclear whether dosage adjustment is necessary when other AEDs and ARVs are combined (Level U). It may be important to avoid enzyme-inducing AEDs in people on ARV regimens that include protease inhibitors or nonnucleoside reverse transcriptase inhibitors, as pharmacokinetic interactions may result in virologic failure, which has clinical implications for disease progression and development of ARV resistance. If such regimens are required for seizure control, patients may be monitored through pharmacokinetic assessments to ensure efficacy of the ARV regimen (Level C).

Spin-polarized inelastic tunneling through insulating barriers

Spin-conserving hopping transport through chains of localized states has been evidenced by taking benefit of the high degree of spin-polarization of CoFeB-MgO-CoFeB magnetic tunnel junctions. In particular, our data show that relatively thick MgO barriers doped with boron favor the activation of spin-conserving inelastic channels through a chain of three localized states and leading to reduced magnetoresistance effects. We propose an extension of the Glazman-Matveev theory to the case of ferromagnetic reservoirs to account for spin-polarized inelastic tunneling through nonmagnetic localized states embedded in an insulating barrier.

Enhancement of the spin accumulation at the interface between a spin-polarized tunnel junction and a semiconductor

We report on spin injection experiments at a Co/Al2O3/GaAs interface with electrical detection. The application of a transverse magnetic field induces a large voltage drop DeltaV at the interface as high as 1.2 mV for a current density of 0.34 nA.microm(-2). This represents a dramatic increase of the spin accumulation signal, well above the theoretical predictions for spin injection through a ferromagnet/semiconductor interface. Such an enhancement is consistent with a sequential tunneling process via localized states located in the vicinity of the Al2O3/GaAs interface. For spin-polarized carriers these states act as an accumulation layer where the spin lifetime is large. A model taking into account the spin lifetime and the escape tunneling time for carriers traveling back into the ferromagnetic contact reproduces accurately the experimental results.

Exchange-mediated anisotropy of (ga,mn)as valence-band probed by resonant tunneling spectroscopy

We report on experiments and theory of resonant tunneling anisotropic magnetoresistance (TAMR) in AlAs/GaAs/AlAs quantum wells (QW) contacted by a (Ga,Mn)As ferromagnetic electrode. Such resonance effects manifest themselves by bias-dependent oscillations of the TAMR signal correlated to the successive positions of heavy (HH) and light (LH) quantized hole energy levels in GaAs QW. We have modeled the experimental data by calculating the spin-dependent resonant tunneling transmission in the frame of the 6 x 6 valence-band k.p theory. The calculations emphasize the opposite contributions of the (Ga,Mn)As HH and LH subbands near the Gamma point, unraveling the anatomy of the diluted magnetic semiconductor valence band.

Spectroscopic measurement of spin-dependent resonant tunneling through a 3D disorder: the case of MnAs/GaAs/MnAs junctions

We propose an analytical model of spin-dependent resonant tunneling through a 3D assembly of localized states (spread out in energy and in space) in a barrier. An inhomogeneous distribution of localized states leads to resonant tunneling magnetoresistance inversion and asymmetric bias dependence as evidenced with a set of experiments with MnAs/GaAs(7-10 nm)/MnAs tunnel junctions. One of the key parameters of our theory is a dimensionless critical exponent beta scaling the typical extension of the localized states over the characteristic length scale of the spatial distribution function. Furthermore, we demonstrate, through experiments with localized states introduced preferentially in the middle of the barrier, the influence of an homogeneous distribution on the spin-dependent transport properties.

Structure of ferromagnetic CrAs epilayers grown on GaAs(001)

Magnetic and structural properties of CrAs epilayers grown on GaAs(001) by molecular beam epitaxy have been studied. CrAs epilayers are orthorhombic for all thicknesses investigated but show a structural transition from a metastable phase for very thin films, to the usual bulk MnP-type orthorhombic phase at higher thicknesses. At intermediate thicknesses, there is a predominance of the new phase, although a contribution from the usual CrAs bulk phase remains clearly present. These results strongly suggest that the ferromagnetic signal measured at room temperature comes from the new metastable orthorhombic structure with an expanded b-axis induced by the substrate strain.

Epitope mapping and specificity of the anti-alpha-synuclein monoclonal antibody Syn-1 in mouse brain and cultured cell lines

While alpha- and beta-synuclein largely overlap in their expression in the vertebrate brain, only alpha-synuclein accumulates in the fibrillar aggregates typical of Parkinson's disease. It is thus critical to have immunological reagents that distinguish between these two protein isoforms. The monoclonal antibody Syn-1 (Transduction Labs) has been frequently used for the specific detection of alpha-synuclein. In this report, the epitope for Syn-1 is localized within residues 91-99 of human alpha-synuclein. Sequence differences exist in this domain that account for the specificity of Syn-1 for alpha- versus beta-synuclein. However, Syn-1 also displays reactivity with additional species (approximately 45 kDa) in brain homogenates from both wild-type and alpha-synuclein null mice, indicating a potential for cross-reactivity with a protein species that is unrelated to alpha-synuclein in brain tissue or extracts.

Electrical detection of spin accumulation in a p-type GaAs quantum well

We report on experiments in which a spin-polarized current is injected from a GaMnAs ferromagnetic electrode into a GaAs layer through an AlAs barrier. The resulting spin polarization in GaAs is detected by measuring how the tunneling current, to a second GaMnAs ferromagnetic electrode, depends on the orientation of its magnetization. Our results can be accounted for by sequential tunneling with the nonrelaxed spin splitting of the chemical potential, that is, spin accumulation, in GaAs. We discuss the conditions on the hole spin relaxation time in GaAs that are required to obtain the large effects we observe.

Magnetism of the Fe/ZnSe(001) interface

The magnetism of epitaxial ultrathin films of Fe on ZnSe(001) has been investigated by x-ray magnetic circular dichroism down to the submonolayer regime. In contrast to other metallic ferromagnet/semiconductor interfaces, no reduction of the Fe magnetic moment was found at the Fe/ZnSe(001) interface. Furthermore, a significant enhancement of the Fe magnetic moment compared to the bulk value was observed for coverages up to one monolayer in agreement with theoretical predictions. We also demonstrate that the magnetic properties of the Fe/ZnSe(001) interface remain stable against thermal annealing up to 300 degrees C, a prerequisite for the future development of efficient spintronics devices.

Exposure to long chain polyunsaturated fatty acids triggers rapid multimerization of synucleins

Detergent-stable multimers of alpha-synuclein have been found specifically in the brains of patients with Parkinson's disease and other neurodegenerative diseases. Here we show that recombinant alpha-synuclein forms multimers in vitro upon exposure to vesicles containing certain polyunsaturated fatty acid (PUFA) acyl groups, including arachidonoyl and docosahexaenoyl. This process occurs at physiological concentrations and much faster than in aqueous solution. PUFA-induced aggregation involves physical association with the vesicle surface via the large apolipoprotein-like lipid-binding domain that constitutes the majority of the protein. beta- and gamma-synucleins, as well as the Parkinson's disease-associated alpha-synuclein variants A30P and A53T, show similar tendencies to multimerize in the presence of PUFAs. Multimerization does not require the presence of any tyrosine residues in the sequence. The membrane-based interaction of the synucleins with specific long chain polyunsaturated phospholipids may be relevant to the protein family's physiological functions and may also contribute to the aggregation of alpha-synuclein observed in neurodegenerative disease.

Protein-protein interactions of alpha-synuclein in brain homogenates and transfected cells

alpha-Synuclein is a highly conserved presynaptic protein with probable roles in normal synaptic development and plasticity as well as neurodegenerative disease, although its molecular function is not yet clear. To identify potential protein binding partners of alpha-synuclein, we performed co-immunoprecipitations using a monoclonal antibody (H3C) against its C-terminus. More than 20 detectable proteins were specifically co-immunoprecipitated from zebra finch and mouse forebrain extracts. One of these, with relative mobility of 55 kDa, was identified through microsequencing as a mixture of alpha- and beta-tubulin. Tubulin was specifically recovered from a mouse forebrain cytosolic extract by a GST/alpha-synuclein fusion protein immobilized on glutathione-Sepharose beads. In the converse experiment, alpha-synuclein bound to a column prepared from purified bovine brain tubulin immobilized upon CNBr-Sepharose. alpha-Synuclein does not appear to bind assembled microtubules, however, as alpha-synuclein did not pellet with polymerized microtubules in a standard assay for microtubule-associated proteins. Likewise, when a fusion construct of alpha-synuclein and green fluorescent protein (GFP) was expressed in African green monkey kidney epithelial (CV-1) cells, the fusion protein did not colocalize with endogenous microtubules. We conclude that alpha-synuclein may interact specifically with heterodimeric tubulin, but not microtubules, in the neuronal cytosol.

When openness to experience and conscientiousness are related to creative behavior: an interactional approach

This study adopted an interactional approach to understanding how 2 of the Five-Factor traits, openness to experience and conscientiousness, are related to creative behavior in the workplace. Openness to experience is theorized to result in high levels of creative behavior and conscientiousness is theorized to result in low levels of creative behavior when the situation allows for the manifestation of the trait influences. More specifically, the authors hypothesized that openness to experience would result in high levels of creative behavior if feedback valence were positive and job holders were presented with a heuristic task that allowed them to be creative. The authors also hypothesized that conscientiousness would result in low levels of creative behavior if supervisors engaged in close monitoring and coworkers were unsupportive. The authors tested their hypotheses in a sample of office workers, and 5 out of the 6 hypotheses were supported.

Interaction of human alpha-Synuclein and Parkinson's disease variants with phospholipids. Structural analysis using site-directed mutagenesis

alpha-Synuclein has been centrally implicated in neurodegenerative disease, and a normal function in developmental synaptic plasticity has been suggested by studies in songbirds. A variety of observations suggest the protein partitions between membrane and cytosol, a behavior apparently conferred by a conserved structural similarity to the exchangeable apolipoproteins. Here we show that the capacity to bind lipids is broadly distributed across exons 3, 4, and 5 (encoding residues 1-102). Binding to phosphatidylserine-containing vesicles requires the presence of all three exons, while binding to phosphatidic acid can be mediated by any one of the three. Consistent with a "class A2" helical binding mechanism, lipid association is disrupted by introduction of charged residues along the hydrophobic face of the predicted alpha-helix and also by biotinylation of conserved lysines (which line the interfacial region). Circular dichroism spectroscopy reveals a general correlation between the amount of lipid-induced alpha-helix content and the degree of binding to PS-containing vesicles. Two point mutations associated with Parkinson's disease have little (A30P) or no (A53T) effect on lipid binding or alpha-helicity. These results are consistent with the hypothesis that alpha-synuclein's normal functions depend on an ability to undergo a large conformational change in the presence of specific phospholipids.

Synucleins in synaptic plasticity and neurodegenerative disorders

Synucleins are small highly conserved proteins in vertebrates, especially abundant in neurons and typically enriched at presynaptic terminals. Three genes in humans produce closely related synuclein proteins, all of which share a large amphipathic domain capable of reversible binding to lipid vesicles. Alpha synuclein has been specifically implicated in neurodegenerative disease. Two point mutations are genetically linked to familial Parkinson's disease, and alpha synuclein appears to form the major fibrillary component of Lewy bodies. Alpha synuclein also contributes to the intracellular inclusions of multiple system atrophy, and a fragment has been found in senile plaques in Alzheimer's disease. Although their normal cellular functions are unknown, several observations suggest the synucleins may serve to integrate presynaptic signaling and membrane trafficking. Alpha synuclein has been identified as a potent and selective inhibitor of phospholipase D2, which produces phosphatidic acid (to which synuclein binds) and is believed to function in the partitioning of membranes between the cell surface and intracellular stores. We outline a hypothesis whereby synuclein supports localized, experience-dependent turnover of synaptic membranes. Such a process may be important for lifelong learning and memory functions and may be especially vulnerable to disruption in aging-associated neurodegenerative diseases.

The reinforced laryngeal mask in paediatric outpatient dental surgery

One hundred and twenty ASA I and II grade children aged 2-9 years scheduled for outpatient dental extractions under general anaesthesia were studied. They were allocated randomly to one of three groups for airway management: group R had anaesthesia with a reinforced laryngeal mask airway, group L with a standard laryngeal mask airway and group N with a nasal mask. Anaesthesia was induced in all children using halothane in 50% nitrous oxide with oxygen and maintained on halothane in 67% nitrous oxide with oxygen. An Ayre's T-piece with Jackson-Rees modification was used. The incidence of airway obstruction was significantly lower and surgical access significantly better with the reinforced laryngeal mask airway when compared with the standard laryngeal mask airway. However, the reinforced laryngeal mask airway was significantly more difficult to insert when compared with the standard laryngeal mask airway. On comparing the reinforced laryngeal mask airway with the nasal mask, there were significantly fewer episodes of airway obstruction, better oxygen saturation, less increase in heart rate and fewer arrhythmias in the reinforced laryngeal mask airway group. Total time for the procedures was the same for all three groups. Thus, the reinforced laryngeal mask airway was found to be a favourable alternative to the standard laryngeal mask airway and nasal mask for paediatric outpatient dental extractions.

The synucleins: a family of proteins involved in synaptic function, plasticity, neurodegeneration and disease

Synuclein proteins are produced, in vertebrates, by three genes. They share structural resemblance to apolipoproteins, but are abundant in the neuronal cytosol and present in enriched amounts at presynaptic terminals. Synucleins have been specifically implicated in three diseases:Alzheimer's (AD), Parkinson's (PD) and breast cancer. In AD, a peptide derived from alpha-synuclein forms an intrinsic component of plaque amyloid. In PD, an alpha-synuclein allele is genetically linked to several independent familial cases, and the protein appears to accumulate in Lewy bodies. In breast cancer, increased expression of gamma-synuclein correlates with disease progression. In songbirds, alpha-synuclein expression is correlated with plasticity in the developing song control system. Although the normal function of synucleins is unknown, a role in membrane plasticity seems likely.

Stabilization of alpha-synuclein secondary structure upon binding to synthetic membranes

alpha-Synuclein is a highly conserved presynaptic protein of unknown function. A mutation in the protein has been causally linked to Parkinson's disease in humans, and the normal protein is an abundant component of the intraneuronal inclusions (Lewy bodies) characteristic of the disease. alpha-Synuclein is also the precursor to an intrinsic component of extracellular plaques in Alzheimer's disease. The alpha-synuclein sequence is largely composed of degenerate 11-residue repeats reminiscent of the amphipathic alpha-helical domains of the exchangeable apolipoproteins. We hypothesized that alpha-synuclein should associate with phospholipid bilayers and that this lipid association should stabilize an alpha-helical secondary structure in the protein. We report that alpha-synuclein binds to small unilamellar phospholipid vesicles containing acidic phospholipids, but not to vesicles with a net neutral charge. We further show that the protein associates preferentially with vesicles of smaller diameter (20-25 nm) as opposed to larger (approximately 125 nm) vesicles. Lipid binding is accompanied by an increase in alpha-helicity from 3% to approximately 80%. These observations are consistent with a role in vesicle function at the presynaptic terminal.

Nigral and cortical Lewy bodies and dystrophic nigral neurites in Parkinson's disease and cortical Lewy body disease contain alpha-synuclein immunoreactivity

A mutation in the alpha-synuclein gene has recently been linked to some cases of familial Parkinson's disease (PD). We characterized the expression of this presynaptic protein in the midbrain, striatum, and temporal cortex of control, PD, and dementia with Lewy bodies (DLB) brain. Control brain showed punctate pericellular immunostaining. PD brain demonstrated alpha-synuclein immunoreactivity in nigral Lewy bodies, pale bodies and abnormal neurites. Rare neuronal soma in PD brain were immunoreactive for alpha-synuclein. DLB cases demonstrated these findings as well as alpha-synuclein immunoreactivity in cortical Lewy bodies and CA2-3 neurites. These results suggest that, even in sporadic cases, there is an early and direct role for alpha-synuclein in the pathogenesis of PD and the neuropathologically related disorder DLB.

An extracellular matrix response element in the promoter of the LpS1 genes of the sea urchin Lytechinus pictus

The extracellular matrix (ECM) has been shown to play an important role in development and tissue-specific gene expression, yet the mechanism by which genes receive signals from the ECM is poorly understood. The aboral ectoderm-specific LpS1-alpha and -beta genes of Lytechinus pictus , members of the Spec gene family, provide an excellent model system to study ECM- mediated gene regulation. Disruption of the ECM by preventing collagen deposition using the lathrytic agent beta-aminopropionitrile (BAPN) inhibits LpS1 gene transcription. LpS1 transcription resumes after removal of BAPN and subsequent collagen reformation. Using a chloramphenicol acetyltransferase (CAT) reporter gene assay, we show that a 125 bp region of the LpS1-beta promoter from -108 to +17 contains an ECM response element (ECM RE). Insertion of the 125 bp region into the promoter of the metallothionein gene of L. pictus, a gene unaffected by ECM disruption, caused the fused promoter to become ECM dependent. As with the endogenous LpS1 genes, CAT activity directed by the fused LpS1-beta promoter resumed in embryos recovered from ECM disruption. A mutation in a cis -acting element called the proximal G-string, which lies in the 125 bp region, caused CAT activity levels in ECM-disrupted embryos to equal that of the wild-type LpS1-bet apromoter in ECM-intact embryos. These results suggest that the intact ECM normally transmits signals to inhibit repressor activity at the proximal G-string in aboral ectoderm cells. Consistent with these results were our findings which showed that in addition to expression in the aboral ectoderm, the proximal G-string mutation caused expression of the CAT gene in oral ectoderm cells. These studies suggested that the proximal G-string serves as a binding site for negative regulation of the LpS1 genes in oral ectoderm during development. We also examined trans -acting factors binding the proximal G-string following ECM disruption. Band shift gels revealed a predominant set of slower migrating nuclear proteins from ECM-disrupted embryos which bound the proximal G-string. This work suggested that ECM disruption initiates signaling that induces a repressor to bind the ECM RE and/or modifies ECM RE binding proteins, which in turn represses LpS1 gene activity.

Delayed localization of synelfin (synuclein, NACP) to presynaptic terminals in cultured rat hippocampal neurons

Synelfin is a presynaptic protein of unknown function that is differentially regulated in the avian song control circuit during the critical period for song learning; in humans, it gives rise to an amyloidogenic peptide found in senile plaques of Alzheimer's disease. To gain insight into the potential involvement of synelfin in synapse development, we investigated its expression in neurons cultured from the embryonic rat hippocampus. These neurons express a variety of defined synaptic proteins, and form numerous synaptic connections after several days in culture. Synapsin I, a synaptic vesicle-associated protein, was detected within one day after the neurons were put in culture, but significant immunoreactivity for synelfin was not detected until approximately 5 days in vitro (DIV). By 3 DIV, synapsin-positive puncta (previously shown to correspond to presynaptic specializations) were detected surrounding the soma and proximal dendritic processes, whereas comparable aggregations of synelfin did not appear until several days later. By 14 DIV the punctate concentrations of synelfin and synapsin overlapped completely. Thus synelfin is expressed in these cultured neurons and eventually becomes localized to presynaptic terminals, but it is absent from these specializations when they first form. We conclude that presynaptic terminals can change in molecular composition, and that synelfin is associated with later stages in synaptic development or modulation.

USF in the Lytechinus sea urchin embryo may act as a transcriptional repressor in non-aboral ectoderm cells for the cell lineage-specific expression of the LpS1 genes

Expression of the aboral ectoderm-specific LpS1 gene in Lytechinus was used to study lineage-specific transcriptional regulation during sea urchin development. Band shift assays using anti-USF antibody showed that a USF-like protein bound the USF core sequence 5'-CACGTG-3' in the promoter of the LpS1 gene. DNA constructs consisting of a wild-type LpS1 promoter and the same LpS1 promoter with a mutated USF binding site fused to the bacterial chloramphenicol acetyltransferase reporter gene were tested. The mutation in the USF binding site caused an increase in chloramphenicol acetyltransferse activity. We selected a clone that encodes USF, LvUSF, from a gastrula-stage cDNA library representing Lytechinus variegatus. Transactivation experiments, in which LvUSF RNA or a DNA construct consisting of the LvUSF cDNA clone fused to the Lytechinus pictus metallothionein promoter coinjected with the wild-type or mutated LpS1 promoter-chloramphenicol acetyltransferase gene construct, showed that chloramphenicol acetyltransferase activity from the wild-type construct was repressed, while the construct mutated at the USF binding site was active. The same wild-type and mutated LpS1 promoter DNA fragments ligated to the green fluorescent protein reporter gene were used to examine spatial expression. The reporter gene constructs containing the mutated USF binding site were expressed inappropriately in all cell types including the gut and oral ectoderm in gastrula and larva stage embryos, while the wild-type constructs were expressed primarily in the aboral ectoderm. USF was expressed in all cells of the early embryo and in all tissues except the aboral ectoderm in later embryos. The data are consistent with a model depicting Lytechinus USF, as a temporal and spatial regulator by repressing LpS1 gene transcription in non-aboral ectoderm cells.

Two distinct forms of USF in the Lytechinus sea urchin embryo do not play a role in LpS1 gene inactivation upon disruption of the extracellular matrix

Recent studies in our laboratory indicated that the upstream stimulatory factor (USF) in the sea urchin embryo of Lytechinus acts as a transcriptional repressor for the aboral ectoderm-specific expression of the LpS1 genes. Disruption of the extracellular matrix (ECM) arrests development prior to gastrulation and inactivates the LpS1 genes. We wanted to determine whether the inactivation of the LpS1 genes by ECM disruption may be due to an increase in USF expression. In the course of the investigation, a second L, variegatus USF cDNA clone (LvUSF2) was isolated and sequenced. The deduced amino acid sequence of LvUSF2 is nearly identical to LvUSF1 except at the amino end, where they are sharply divergent. Like LvUSF1, LvUSF2 has a USF-specific, a basic/hefixloop-helix, and a leucine zipper domain. Genomic DNA blots indicated that the two cDNA clones are derived from one gene, which suggested that the Lytechinus USF1 and USF2 mRNAs, of approximately 6.0 and 4.0 kb, respectively, are the result of differential RNA splicing. ECM disruption in Lytechinus embryos caused a relative drop in USF RNA accumulation levels to approximately 60% of control embryos, while LpS1 RNA accumulation levels dropped to less than 5%. USF protein levels and DNA binding activities in ECM-disrupted embryos also dropped to approximately 60% to that of control embryos. A mutation at the USF binding site in an LpS1 promoter-chloramphenicol acetyl transferase (CAT) fusion DNA construct did not cause a relative increase in CAT activity in ECM disrupted embryos. These results suggest that the induced drop in LpS1 gene expression by ECM disruption is not due to an increase in the repressive activity of USF.

Characterization of the precursor protein of the non-A beta component of senile plaques (NACP) in the human central nervous system

A novel and highly conserved presynaptic protein has been independently described in rodents (synuclein/SYN-1), songbirds (synelfin), and humans (the precursor protein of the non-A beta component of senile plaques, NACP); a fragment of the latter has been detected in senile plaques in Alzheimer's disease (AD). We characterized the expression of NACP in human AD and non-AD brain. A subcellular fractionation study demonstrated that NACP was mainly localized to cytosolic fractions of human temporal cortex. NACP was also detectable in various membrane and vesicular fractions, suggesting that the protein was associated with membrane structures including synaptic vesicles. Pericellular immunostaining of the neuropil was observed in neocortical and limbic regions, supporting a synaptic localization. Senile plaques in AD brains were not immunoreactive, and confocal microscopy suggested a loss of NACP immunoreactivity in cored plaques. No difference was found in the amount of protein in AD and control frontal cortex, as measured by immunoblotting. PCR analysis showed that the full-length mRNA product was the major splice form in both AD and control human brains. Thus, despite the association of a hydrophobic fragment of NACP with senile plaques, our data suggest that the precursor itself is not a significant component of plaques and NACP synthesis is not substantially altered in AD. Nevertheless, the protein is an abundant component of synaptic regions prone to degeneration in AD, and may have a role in the expression or advancement of the disease.

The experience of work and turnover intentions: interactive effects of value attainment, job satisfaction, and positive mood

The researchers proposed that the phenomenological experience of work is multifaceted and that simultaneously considering the combined effects of the different aspects of the work experience holds considerable promise for increasing understanding of turnover intentions and other organizationally relevant outcomes. Research in subjective well-being and other areas suggests that there are 3 important aspects of the experience of work: attainment of values, attitudes, and moods. It was hypothesized and found that the relationship between job satisfaction and turnover intentions is jointly moderated by value attainment and positive mood. The nature of this triple interaction was such that the job satisfaction-turnover intention relationship was strongest when workers' jobs did not help them to attain terminal values and positive moods were experienced, and the relationship was weakest when jobs helped workers to attain terminal values and positive moods were experienced.

An ECM-bound, PDGF-like growth factor and a TGF-alpha-like growth factor are required for gastrulation and spiculogenesis in the Lytechinus embryo

Growth factors and the extracellular matrix have been shown to fulfill vital developmental roles in many embryonic systems. Our hypothesis is that a developmental role played by the extracellular matrix in sea urchins may be the binding of a PDGF-like growth factor to promote signaling activity. We report here that anti-human PDGF-B antibodies and anti-human TGF-alpha antibodies immunoprecipitated specific proteins isolated from Lytechinus embryos. Addition of these antibodies to Lytechinus embryos inhibited gastrulation and spiculogenesis. The embryos are sensitive to the antibodies from the four-cell through the hatching blastula stages, which suggests that the TGF-alpha-like and PDGF-like ligands are required for the early differentiation of the gut and spicules. We present evidence that the PDGF-like growth factor depends on the extracellular matrix for signaling activity. Synthetic peptides representing the heparan sulfate proteoglycan binding sequence on human PDGF-B were added to Lytechinus embryo cultures to compete for binding sites with the endogenous PDGF-like growth factor. The experimental peptide inhibited gastrulation and caused radially arranged multiple spicules to form. Development was unaffected by a control peptide. These studies support our hypothesis and suggest that TGF-alpha-like and PDGF-like growth factors induce signaling events required for sea urchin gastrulation and spiculogenesis and suggest that an extracellular matrix-associated PDGF-like growth factor is involved in differentiation along the oral-aboral axis.

Postoperative hypoxaemia during transport and in the recovery area

This study was undertaken to ascertain the incidence of postoperative hypoxaemia in the recovery area and during transfer to the recovery area while adhering to the current practice of anaesthesia and recovery room care. Attempts were also made to determine some of the risk factors for the development of hypoxaemia. There were 546 patients who had general or regional anaesthesia observed in the recovery area and of these, 534 patients were also observed during transfer using Critikon Oxyshuttle pulse oximeters. The incidence of hypoxaemia (SpO2 < or = 90%) and severe hypoxaemia (SpO2 < or = 85%) during transfer were 10.11% and 2.06% respectively. The incidence of hypoxaemia and severe hypoxaemia in the recovery area were 8.42% and 2.2% respectively. No oxygen was given to patients during transfer. In the recovery area, 322 patients (58.97%) had oxygen therapy and 224 patients (41.03%) did not. The occurrence of hypoxaemia during transfer was significantly related to the duration of surgery. In the recovery area, age and weight were found to be statistically significant risk factors. The incidence of hypoxaemia in this study is much lower than that reported in other studies.

Correspondence between sites of NGFI-A induction and sites of morphological plasticity following exposure to environmental complexity

To determine if gene regulation may play a role in behaviorally-induced morphological plasticity in the brain, we used in situ hybridization to measure levels of mRNA for the immediate early gene transcription factor NGFI-A (also known as ZENK, zif/268, egr-1 and Krox 24). Brains of periadolescent male rats exposed to 2-4 days of the following behavioral treatments were compared: (1) group housing in a complex environment (EC); (2) individual housing with daily handling (HIC); and (3) individual handling (IC). Quantitative analysis of the autoradiograms revealed that EC rats had significantly higher levels of NGFI-A than IC rats in regions of cortex previously shown to exhibit morphological plasticity (most pronounced in visual cortex), but not in frontal cortex where no dendritic changes have been detected. HIC rats were intermediate between the two groups. These data support an association between structural plasticity and altered patterns of immediate early gene expression.

Characterization of a novel protein regulated during the critical period for song learning in the zebra finch

A male zebra finch learns a song by listening to a tutor, but song learning is normally restricted to a critical period in juvenile development. Here we identify an RNA whose expression in the song control circuit is altered during this critical period. The RNA encodes a soluble presynaptic protein that forms a predicted amphipathic alpha helix typical of the lipid-binding domain in apolipoproteins. We show this protein, which we call synelfin, to be the homolog of the human non-A beta component (and its precursor) recently purified from Alzheimer's disease amyloid. We suggest this highly conserved protein may serve a novel function critical to the regulation of vertebrate neural plasticity.

Correlations between the Hand Test Pathology score and Personality Assessment Inventory scales for pain clinic patients

Pearson correlations between the Hand Test Pathology (PATH) score and Personality Assessment Inventory scales produced a cluster of relationships characteristic of an antisocial orientation. Likewise, PATH significantly differentiated between a "P" (Pathology) group flagged by a high Negative Impression score on the inventory, and an "N" (Normal) group of 100 pain patients. It was suggested that the interpretive simplicity of Hand Test scores renders the scores amenable to further correlational studies involving the inventory.

Immediate-early gene responses in the avian song control system: cloning and expression analysis of the canary c-jun cDNA

Previous studies have shown that song presentation results in a rapid rise in mRNA levels for the ZENK gene (the avian homologue of zif-268, Egr-1, NGFI-A, and Krox-24) in specific parts of the songbird forbrain. Metrazole-induced seizures also cause an increase in ZENK mRNA, even more widely throughout the telencephalon. Surprisingly, however, little or no ZENK induction by either stimulus was observed in several forebrain areas involved in auditory processing and song production. To learn whether this pattern of regulation is specific to ZENK, we examined the response of another 'immediate-early' gene, c-jun. Here we first describe the identification, cloning and sequence analysis of a canary cDNA encoding c-jun. Then, by in situ hybridization we show that c-jun is also induced by song or seizure, and in a pattern mostly similar to ZENK. As with ZENK, no induction of c-jun is observed in the androgen receptor-containing song nuclei or within the primary thalamo-recipient auditory area of the forebrain. Thus common immediate early gene responses appear to be selectively uncoupled from physiological activation in these specific forebrain regions, which are also characterized by tight developmental, hormonal and seasonal regulation.

The role of negative affectivity in understanding relations between self-reports of stressors and strains: a comment on the applied psychology literature

On the basis of a brief review of the health, organizational, and personality psychology literatures supportive of the expectation that observed relations between self-reports of stressors and strains are influenced by the mood-dispositional dimension negative affectivity (NA), reanalyses of four data sets were conducted. The results of these reanalyses, contrary to the assertions of several authors in the applied psychology literature, offered further support for the hypothesized "nuisance" properties of NA in studies involving relations between self-reports of stressors and strain. A discussion of how NA and other mood-dispositional dimensions may be of interest to investigators concerned with relations between self-reports of any condition of employment and any affective state of workers is presented.

Integrating bottom-up and top-down theories of subjective well-being: the case of health

As a means of integrating bottom-up and top-down theories of subjective well-being (SWB), a framework was proposed that, in part, posits that both objective life circumstances and global personality dimensions indirectly affect SWB through their effects on the interpretation of life circumstances. This proposition was tested both cross-sectionally and longitudinally among a sample of approximately 375 men and women. Personality was operationalized in terms of the dispositional trait negative affectivity (NA), and the life circumstance investigated was health. Strong support was obtained for the hypothesized indirect effects of NA and objective health on SWB. Implications of the integrative framework for the study of SWB are discussed.