Coexisting Charge-Ordered States with Distinct Driving Mechanisms in Monolayer VSe2

Thinning crystalline materials to two dimensions (2D) creates a rich playground for electronic phases, including charge, spin, superconducting, and topological order. Bulk materials hosting charge density waves (CDWs), when reduced to ultrathin films, have shown CDW enhancement and tunability. However, charge order confined to only 2D remains elusive. Here we report a distinct charge ordered state emerging in the monolayer limit of 1T-VSe₂. Systematic scanning tunneling microscopy experiments reveal that bilayer VSe₂ largely retains the bulk electronic structure, hosting a tridirectional CDW. However, monolayer VSe₂ ─consistently across distinct substrates─exhibits a dimensional crossover, hosting two CDWs with distinct wavelengths and transition temperatures. Electronic structure calculations reveal that while one CDW is bulk-like and arises from the well-known Peierls mechanism, the other is decidedly unconventional. The observed CDW-lattice decoupling and the emergence of a flat band suggest that the second CDW could arise from enhanced electron-electron interactions in the 2D limit. These findings establish monolayer-VSe₂ as a host of coexisting charge orders with distinct origins, and enable the tailoring of electronic phenomena via emergent interactions in 2D materials.

Room Temperature Ferromagnetism of Monolayer Chromium Telluride with Perpendicular Magnetic Anisotropy

The realization of long-range magnetic ordering in 2D systems can potentially revolutionize next-generation information technology. Here, the successful fabrication of crystalline Cr₃ Te₄ monolayers with room temperature (RT) ferromagnetism is reported. Using molecular beam epitaxy, the growth of 2D Cr₃ Te₄ films with monolayer thickness is demonstrated at low substrate temperatures (≈100 °C), compatible with Si complementary metal oxide semiconductor technology. X-ray magnetic circular dichroism measurements reveal a Curie temperature (T_c ) of v344 K for the Cr₃ Te₄ monolayer with an out-of-plane magnetic easy axis, which decreases to v240 K for the thicker film (≈7 nm) with an in-plane easy axis. The enhancement of ferromagnetic coupling and the magnetic anisotropy transition is ascribed to interfacial effects, in particular the orbital overlap at the monolayer Cr₃ Te₄ /graphite interface, supported by density-functional theory calculations. This work sheds light on the low-temperature scalable growth of 2D nonlayered materials with RT ferromagnetism for new magnetic and spintronic devices.

Diverse Structures and Magnetic Properties in Nonlayered Monolayer Chromium Selenide

Thickness-dependent magnetic behavior has previously been observed in chemical vapor deposition-grown chromium selenide. However, the low-dimensional structure in nonlayered chromium selenide, which plays a crucial role in determining the low-dimensional magnetic order, needs further study. Here, we report the structure-dependent magnetic properties in monolayer CrSe₂ and Cr₂Se₃ grown by molecular beam epitaxy. In the monolayer CrSe₂, 1T-CrSe₂ with a lattice constant of 3.3 Å has a metallic character, coexisting with the 1T″ phase with 2 × 2 surface periodicity. Monolayer CrSe₂ can be transformed into Cr₂Se₃ with a lattice constant of 3.6 Å by annealing at 300 °C. X-ray magnetic circular dichroism (XMCD) measurements combined with DFT calculations reveal that while the MBE-grown monolayer CrSe₂ is antiferromagnetic, monolayer Cr₂Se₃ is ferromagnetic with a Curie temperature of ∼200 K. This work demonstrates the structural diversity in nonlayered chromium selenide and the critical effect of different structures on its electronic and magnetic properties.

Can Reconstructed Se-Deficient Line Defects in Monolayer VSe2 Induce Magnetism?

There have been several recent conflicting reports on the ferromagnetism of clean monolayer VSe₂ . Herein, the controllable formation of 1D defect line patterns in vanadium diselenide (VSe₂ ) monolayers initiated by thermal annealing is presented. Using scanning tunneling microscopy and q-plus atomic force microscopy techniques, the 1D line features are determined to be 8-member-ring arrays, formed via a Se deficient reconstruction process. The reconstructed VSe₂ monolayer with Se-deficient line defects displays room-temperature ferromagnetism under X-ray magnetic circular dichroism and magnetic force microscopy, consistent with the density functional theory calculations. This study possibly resolves the controversy on whether ferromagnetism is intrinsic in monolayer VSe₂ , and highlights the importance of controlling and understanding the atomic structures of surface defects in 2D crystals, which could play key roles in the material properties and hence potential device applications.

Selective self-assembly of 2,3-diaminophenazine molecules on MoSe2 mirror twin boundaries

The control of the density and type of line defects on two-dimensional (2D) materials enable the development of new methods to tailor their physical and chemical properties. In particular, mirror twin boundaries (MTBs) on transition metal dichacogenides have attracted much interest due to their metallic state with charge density wave transition and spin-charge separation property. In this work, we demonstrate the self-assembly of 2,3-diaminophenazine (DAP) molecule porous structure with alternate L-type and T-type aggregated configurations on the MoSe2 hexagonal wagon-wheel pattern surface. This site-specific molecular self-assembly is attributed to the more chemically reactive metallic MTBs compared to the pristine semiconducting MoSe2 domains. First-principles calculations reveal that the active MTBs couple with amino groups in the DAP molecules facilitating the DAP assembly. Our results demonstrate the site-dependent electronic and chemical properties of MoSe2 monolayers, which can be exploited as a natural template to create ordered nanostructures.

Evidence of Spin Frustration in a Vanadium Diselenide Monolayer Magnet

Monolayer VSe₂ , featuring both charge density wave and magnetism phenomena, represents a unique van der Waals magnet in the family of metallic 2D transition-metal dichalcogenides (2D-TMDs). Herein, by means of in situ microscopy and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, direct spectroscopic signatures are established, that identify the metallic 1T-phase and vanadium 3d¹ electronic configuration in monolayer VSe₂ grown on graphite by molecular-beam epitaxy. Element-specific X-ray magnetic circular dichroism, complemented with magnetic susceptibility measurements, further reveals monolayer VSe₂ as a frustrated magnet, with its spins exhibiting subtle correlations, albeit in the absence of a long-range magnetic order down to 2 K and up to a 7 T magnetic field. This observation is attributed to the relative stability of the ferromagnetic and antiferromagnetic ground states, arising from its atomic-scale structural features, such as rotational disorders and edges. The results of this study extend the current understanding of metallic 2D-TMDs in the search for exotic low-dimensional quantum phenomena, and stimulate further theoretical and experimental studies on van der Waals monolayer magnets.

Ferromagnet/Two-Dimensional Semiconducting Transition-Metal Dichalcogenide Interface with Perpendicular Magnetic Anisotropy

Ferromagnet/two-dimensional transition-metal dichalcogenide (FM/2D TMD) interfaces provide attractive opportunities to push magnetic information storage to the atomically thin limit. Existing work has focused on FMs contacted with mechanically exfoliated or chemically vapor-deposition-grown TMDs, where clean interfaces cannot be guaranteed. Here, we report a reliable way to achieve contamination-free interfaces between ferromagnetic CoFeB and molecular-beam epitaxial MoSe₂. We show a spin reorientation arising from the interface, leading to a perpendicular magnetic anisotropy (PMA), and reveal the CoFeB/2D MoSe₂ interface allowing for the PMA development in a broader CoFeB thickness-range than common systems such as CoFeB/MgO. Using X-ray magnetic circular dichroism analysis, we attribute generation of this PMA to interfacial d-d hybridization and deduce a general rule to enhance its magnitude. We also demonstrate favorable magnetic softness and considerable magnetic moment preserved at the interface and theoretically predict the interfacial band matching for spin filtering. Our work highlights the CoFeB/2D MoSe₂ interface as a promising platform for examination of TMD-based spintronic applications and might stimulate further development with other combinations of FM/2D TMD interfaces.

From adaptive licensing to adaptive pathways: delivering a flexible life-span approach to bring new drugs to patients

The concept of adaptive licensing (AL) has met with considerable interest. Yet some remain skeptical about its feasibility. Others argue that the focus and name of AL should be broadened. Against this background of ongoing debate, we examine the environmental changes that will likely make adaptive pathways the preferred approach in the future. The key drivers include: growing patient demand for timely access to promising therapies, emerging science leading to fragmentation of treatment populations, rising payer influence on product accessibility, and pressure on pharma/investors to ensure sustainability of drug development. We also discuss a number of environmental changes that will enable an adaptive paradigm. A life‐span approach to bringing innovation to patients is expected to help address the perceived access vs. evidence trade‐off, help de‐risk drug development, and lead to better outcomes for patients.

Cortical involvement in the StartReact effect

The rapid release of prepared movements by a loud acoustic stimulus capable of eliciting a startle response has been termed the StartReact effect (Valls-Solé et al., 1999), and premotor reaction times (PMTs) of <70 ms are often observed. Two explanations have been given for these short latency responses. The subcortical storage and triggering hypothesis suggests movements that can be prepared in advance of a "go" signal are stored and triggered from subcortical areas by a startling acoustic stimulus (SAS) without cortical involvement. Alternatively, it has been hypothesized that the SAS can trigger movements from cortical areas through a faster pathway ascending from subcortical structures. Two experiments were designed to examine the possible role of the primary motor cortex in the StartReact effect. In Experiment 1, we used suprathreshold transcranial magnetic stimulation (TMS) during the reaction time (RT) interval to induce a cortical silent period in the contralateral primary motor cortex (M1). Thirteen participants performed 20° wrist extension movements as fast as possible in response to either a control stimulus (82 dB) or SAS (124 dB). PMTs for startle trials were faster than for control trials, while TMS significantly delayed movement onset compared to No TMS or Sham TMS conditions. In Experiment 2, we examined the StartReact effect in a highly cortically represented action involving speech of a consonant-vowel (CV) syllable. Similar to previous work examining limb movements, a robust StartReact effect was found. Collectively, these experiments provide evidence for cortical (M1) involvement in the StartReact effect.

First trial and StartReact effects induced by balance perturbations to upright stance

Postural responses (PR) to a balance perturbation differ between the first and subsequent perturbations. One explanation for this first trial effect is that perturbations act as startling stimuli that initiate a generalized startle response (GSR) as well as the PR. Startling stimuli, such as startling acoustic stimuli (SAS), are known to elicit GSRs, as well as a StartReact effect, in which prepared movements are initiated earlier by a startling stimulus. In this study, a StartReact effect paradigm was used to determine if balance perturbations can also act as startle stimuli. Subjects completed two blocks of simple reaction time trials involving wrist extension to a visual imperative stimulus (IS). Each block included 15 CONTROL trials that involved a warning cue and subsequent IS, followed by 10 repeated TEST trials, where either a SAS (TESTSAS) or a toes-up support-surface rotation (TESTPERT) was presented coincident with the IS. StartReact effects were observed during the first trial in both TESTSAS and TESTPERT conditions as evidenced by significantly earlier wrist movement and muscle onsets compared with CONTROL. Likewise, StartReact effects were observed in all repeated TESTSAS and TESTPERT trials. In contrast, GSRs in sternocleidomastoid and PRs were large in the first trial, but significantly attenuated over repeated presentation of the TESTPERT trials. Results suggest that balance perturbations can act as startling stimuli. Thus first trial effects are likely PRs which are superimposed with a GSR that is initially large, but habituates over time with repeated exposure to the startling influence of the balance perturbation.

Startle induces early initiation of classically conditioned postural responses

Startling acoustic stimuli (SAS) induce the early release of prepared motor responses. The current study used SAS, in conjunction with a classical conditioning paradigm, to examine advanced motor preparation of conditioned postural responses (PRs). After generalized startle responses were induced, standing posture was perturbed in 2 blocks of 15 Conditioning trials, where in each trial the onset of a nonstartling auditory cue [i.e., a conditioned stimulus (CS)] preceded a leftward support-surface translation. Upon completion of each block, a single trial was conducted. After block 1, a CS-Only trial was used to induce conditioned PRs in the absence of balance perturbations. After block 2, a post-Conditioning Startle trial that involved a CS subsequently followed by a SAS was used to examine motor preparation of conditioned PRs. PRs were quantified in terms of center of pressure displacements, ankle and hip kinematics, as well as surface electromyography of proximal and distal bilateral muscle pairs. Results indicated that repeated experience with cued balance perturbations led to PR conditioning and, more importantly, motor preparation of PRs. Conditioning was evidenced in biomechanical and electromyographic responses observed in CS-Only trials, as well as the progressive changes to evoked response parameters during repeated Conditioning trials. SAS presented in post-Conditioning Startle trials evoked early onsets of biomechanical and electromyographic responses, while preserving relative response parameters that were each distinct from generalized startle responses. These results provide important insight into both the consequences of using cues in dynamic postural control studies and the neural mechanisms governing PRs.

Will "no blood" kill Jehovah Witnesses?

A 46-year-old Indonesian woman presented with signs and symptoms suggestive of an ovarian tumour and was advised to have surgery with exploratory laparotomy and removal of the mass. She agreed but refused blood transfusion any time in the course of her treatment or procedure, as she was a Jehovah Witness. As there was a high risk of intraoperative haemorrhage, steps were taken to reduce any consequent complications due to the surgery. The ethical conflict is between respecting patient autonomy and compromising standards of care, arising from the refusal of a standard therapy. The latest developments in the blood transfusion doctrine policy for the Jehovah Witnesses are also discussed in this case study.

Comparison and validation of three measures of quality of life in patients with pulmonary hypertension

BACKGROUND

Pulmonary hypertension, when advanced, markedly limits exercise capacity, activities of daily living and quality of life (QoL). No measure of QoL has yet been validated for the assessment of pulmonary hypertension. The aim of the study was to compare the validity of the Minnesota Living with Heart Failure (MLwHF) questionnaire, the Short Form-36 (SF-36) questionnaire and the Australian Quality of Life (AQoL) measure for assessing pulmonary hypertension treatment.

METHODS

Eighty-three patients were enrolled in three studies of pulmonary hypertension treatment (treprostinil, bosentan and sildenafil). They were assessed at baseline and 3 months with the MLwHF questionnaire. Treprostinil and bosentan groups also had 6 and 12 months' data. Twenty-one patients in the sildenafil trial completed concurrently, the SF-36 and AQoL measures at baseline and 3 months. QoL scores were correlated with the 6-min walk test distance, New York Heart Association functional class and right heart catheter-derived haemodynamic parameters of the disease for all matching time points and for changes in scores and clinical measurements over time.

RESULTS

The MLwHF and SF-36 scores correlated well with the 6-min walk test distance and New York Heart Association functional class, but did not correlate with haemodynamic measurements. MLwHF and SF-36 scores also correlated with the rate of change of the 6-min walk test distance and New York Heart Association functional class over time.

CONCLUSION

The MLwHF questionnaire and SF-36 are useful tools for the assessment of QoL in pulmonary hypertension and may be useful in the ongoing evaluation of QoL in the treatment and study of pulmonary hypertension.

Touch noise increases vibrotactile sensitivity in old and young

Stochastic resonance (SR) occurs when the detection of a subthreshold signal is aided by the presence of random energy fluctuations in the signal modality, commonly called noise. SR is counterintuitive because such noise usually worsens performance. Nonetheless, SR has been demonstrated both theoretically and experimentally in human sensory systems. Using a psychophysically sophisticated paradigm, we show that SR aids the detection of vibrating touch stimuli presented to the foot soles of both healthy elderly people with elevated vibrotactile thresholds and healthy young people with normal vibrotactile thresholds. The results also suggest that it is possible to know a priori the amount of noise needed for optimal SR effects given the degree to which the signal is subthreshold. Thus, SR may be practical as a rehabilitative aid for individuals with elevated sensory thresholds.

A cohort study of early neurological consultation by telemedicine on the care of neurological inpatients

OBJECTIVES

To find out the effect of early neurological consultation using a real time video link on the care of patients with neurological symptoms admitted to hospitals without neurologists on site.

METHODS

A cohort study was performed in two small rural hospitals: Tyrone County Hospital (TCH), Omagh, and Erne Hospital, Enniskillen. All patients over 12 years of age who had been admitted because of neurological symptoms, over a 24 week period, to either hospital were studied. Patients admitted to TCH, in addition to receiving usual care, were offered a neurological consultation with a neurologist 120 km away at the Neurology Department of the Royal Victoria Hospital, Belfast, using a real time video link. The main outcome measure was length of hospital stay; change of diagnosis, mortality at 3 months, inpatient investigation, and transfer rate and use of healthcare resources within 3 months of admission were also studied.

RESULTS

Hospital stay was significantly shorter for those admitted to TCH (hazard ratio 1.13; approximate 95% CI 1.003 to 1.282; p = 0.045). No patients diagnosed by the neurologist using the video link subsequently had their diagnosis changed at follow up. There was no difference in overall mortality between the groups. There were no differences in the use of inpatient hospital resources and medical services in the follow up period between TCH and Erne patients.

CONCLUSIONS

Early neurological assessment reduces hospital stay for patients with neurological conditions outside of neurological centres. This can be achieved safely at a distance using a real time video link.

Email triage of new neurological outpatient referrals from general practice

OBJECTIVES

To determine whether an email triage system between general practitioners and a neurologist for new outpatient referrals is feasible, acceptable, efficient, safe, and effective.

METHODS

This was a prospective single cohort study on the interface between primary care practitioners and the neurology clinic of a district general hospital. Seventy six consecutive patients with neurological symptoms from nine GPs, for whom a specialist opinion was deemed necessary, were entered in the study. The number of participants managed without clinic attendance and the reduction in neurologist's time compared with conventional consultation was measured, as was death, other specialist referral, and change in diagnosis in the 6 months after episode completion. The acceptability for GPs was ascertained by questionnaire.

RESULTS

Forty three per cent of participants required a clinic appointment, 45% were managed by email advice alone, and 12% by email plus investigations. GP satisfaction was high. Forty four per cent of the neurologist's time was saved compared with conventional consultation. No deaths or significant changes in diagnosis were recorded during the 6 month follow up period.

CONCLUSIONS

Email triage is feasible, acceptable to GPs, and safe. It has the potential for making the practice of neurologists more efficient, and this needs to be tested in a larger randomised study.

Influence of terminal action requirements on action-centered distractor effects

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

Cost implications of outpatient teleneurology

A randomized controlled trial was conducted to compare the costs of realtime teleneurology with the cost of conventional neurological care. Two district hospitals in Northern Ireland were equipped with videoconferencing units and were connected to the regional neurological centre by ISDN at 384 kbit/s. Of 168 patients randomized to the study, 141 kept their appointments (76 male, 65 female). Sixty-five patients were randomized to a conventional consultation while 76 were randomized to a teleconsultation. The average age was 44 years of those seen conventionally and 42 years of those seen by telemedicine. The groups had similar diagnoses. The telemedicine group required more investigations and reviews than the conventional group. The average cost of the conventional consultation was 49 pounds sterling compared with 72 pounds sterling for the teleconsultation. Realtime teleneurology was not as cost-effective as conventional care.

Eye-hand coordination in goal-directed aiming

In a number of studies, we have demonstrated that the spatial-temporal coupling of eye and hand movements is optimal for the pickup of visual information about the position of the hand and the target late in the hand's trajectory. Several experiments designed to examine temporal coupling have shown that the eyes arrive at the target area concurrently with the hand achieving peak acceleration. Between the time the hand reached peak velocity and the end of the movement, increased variability in the position of the shoulder and the elbow was accompanied by a decreased spatial variability in the hand. Presumably, this reduction in variability was due to the use of retinal and extra-retinal information about the relative positions of the eye, hand and target. However, the hand does not appear to be a slave to the eye. For example, we have been able to decouple eye movements and hand movements using Müller-Lyer configurations as targets. Predictable bias, found in primary and corrective saccadic eye movements, was not found for hand movements, if on-line visual information about the target was available during aiming. That is, the hand remained accurate even when the eye had a tendency to undershoot or overshoot the target position. However, biases of the hand were evident, at least in the initial portion of an aiming movement, when vision of the target was removed and vision of the hand remained. These findings accent the versatility of human motor control and have implications for current models of visual processing and limb control.

Human interlimb reflexes evoked by electrical stimulation of cutaneous nerves innervating the hand and foot

There is some discrepancy over the extent to which reflex pathways from different cutaneous nerves in the hand and foot link the cervical and lumbar spinal cord in neurologically intact humans. The present experiments were designed to determine whether stimulation of a cutaneous nerve in the foot or in the hand evoked reflexes in the non-stimulated limbs (interlimb reflexes). Reflexes were elicited by stimulating (5x1-ms pulses at 300 Hz) the superficial peroneal (SP; innervates the foot dorsum) or superficial radial (SR; innervates the dorsolateral portion of the hand) nerve while subjects (n=10) performed focused contractions of different upper and lower limb muscles. Reflex responses were divided into early (<75 ms), middle (75-120 ms), and late (>120 ms) epochs as determined from averages of 50 sweeps of stimulus-locked electromyographic activity. Significant interlimb reflexes were found at the early latency in 44/106 and 44/103 muscles sampled after SP and SR nerve stimulation, respectively. At the middle latency, significant interlimb reflexes were seen in 89/106 and 87/103 muscles sampled after SP and SR nerve stimulation, respectively. Interlimb reflexes were seen when stimulating at the wrist (i.e. SR nerve) and when stimulating at the ankle (i.e. SP nerve) with an equal probability. The results show that interlimb cutaneous reflexes are widely distributed in humans. The mean latency of the earliest response was quite short and may be mediated by a propriospinal pathway. Functionally, these pathways may provide a substrate for transferring information to coordinate movements between the limb segments.

Randomised controlled trial of telemedicine for new neurological outpatient referrals

OBJECTIVE

To test the hypothesis that telemedicine for new patient referrals to neurological outpatients is as efficient and acceptable as conventional face to face consultation.

METHODS

A randomised controlled trial between two groups: face to face (FF) and telemedicine (TM). This study was carried out between a neurological centre and outlying clinics at two distant hospitals linked by identical medium cost commercial interactive video conferencing equipment with ISDN lines transmitting information at 384 kbits/s. The same two neurologists carried out both arms of the study. Of the 168 patients who were suitable for the study, 86 were randomised into the telemedicine group and 82 into the face to face group. Outcome measures were (1) consultation process: (a) number of investigations; (b) number of drugs prescribed; (c) number of patient reviews and (2) patient satisfaction: (a) confidence in consultation; (b) technical aspects of consultation; (c) aspects surrounding confidentiality. Diagnostic categories were also measured to check equivalence between the groups: these were structural neurological, structural non-neurological, non-structural, and uncertain.

RESULTS

Diagnostic categories were similar (p>0.5) between the two groups. Patients in the telemedicine group had significantly more investigations (p=0.001). There was no difference in the number of drugs prescribed (p>0.5). Patients were generally satisfied with both types of consultation process except for concerns about confidentiality and embarrassment in the telemedicine group (p=0.017 and p=0.005 respectively).

CONCLUSION

Telemedicine for new neurological outpatients is possible and feasible but generates more investigations and is less well accepted than face to face examination.

Influence of operator orientation on relative organizational mapping and spatial compatibility

Following up on a study by Worringham and Beringer (1989) that examined the influence of operator orientation on visual-motor performance, Experiment 1 employed a choice reaction time paradigm in which participants had to make rapid, discrete movements with a lever in response to a discrete stimulus. In Experiment 2, participants had to synchronize rhythmic movements with an oscillating visual display. Operator orientation with respect to stimulus display and response array locations was varied to examine the influence of global spatial relations. Display orientation was varied to examine the influence of spatial configuration. Mapping rules were varied to examine the effects of spatial mapping. In Experiment 1, the spatial mapping that yielded faster responses was dependent upon the stimulus display-response array configuration and the global relation. Under a parallel configuration, participants appeared to code the spatial aspects of the stimulus display and response in a manner that was unaffected by the global spatial relation. Under an orthogonal configuration, spatial mapping effects were dependent upon the global relation. In Experiment 2, the global spatial relation did not have an impact on the uniformity of co-ordination under different configuration or mapping conditions. Spatial configuration influenced whether or not differences between spatial mapping rules emerged. Together, the results speak to the relative nature of stimulus-response coding that underlie compatibility phenomena. In addition, the results have potential importance for the design of human-machine systems that allow flexibility in operator orientation.

Visual awareness and the on-line modification of action

An influential theory of visually guided action proposes that (a) conscious perception of target displacement disrupts on-line action and (b) small target perturbations are inconsequential, provided the participant is unaware of them. This study examined these claims in a study of rapid aiming movements to targets. Novel features included on-line verbal reports of target displacement, and the factorial combination of small versus large displacements occurring near peak saccadic velocity or 100 ms later. Although awareness of target displacement had no effect on movement kinematics, even small target displacements near peak saccadic velocity affected kinematic measures. These results support both a strong view of visual stream separation in the on-line control of action and richer spatial coding by unconscious processes than has previously been acknowledged.

A century later: Woodworth's (1899) two-component model of goal-directed aiming

In 1899, R. S. Woodworth published a seminal monograph, "The Accuracy of Voluntary Movement." As well as making a number of important empirical contributions, Woodworth presented a model of speed-accuracy relations in the control of upper limb movements. The model has come to be known as the two-component model because the control of speeded limb movements was hypothesized to entail both a central and a feedback-based component. Woodworth's (1899) ideas about the control of rapid aiming movements are evaluated in the context of current empirical and theoretical contributions.

Differential regulation of cutaneous and H-reflexes during leg cycling in humans

Reflexes undergo modulation according to task and timing during standing, walking, running, and leg cycling in humans. Both cutaneous and Hoffman (H-) reflexes are modulated by movement and task. However, recent evidence suggests that the modulation pattern for cutaneous and H-reflexes may be different. We sought to clarify this issue by reducing the effect of movement phase and altering the level of background muscle activation (low and high) in static and dynamic (leg cycling) conditions. Electromyography was recorded from the ankle extensors soleus and medial gastrocnemius (MG) and the knee extensor vastus lateralis (VL). Reflexes were evoked during the downstroke of stationary leg cycling. Cutaneous reflexes were evoked with trains of 5 x 1.0 ms pulses at 300 Hz delivered to the distal tibial nerve, whereas H-reflexes were evoked in soleus by stimulation with single 1.0-ms pulses. There were two main observations in this study: 1) middle latency cutaneous reflexes were facilitatory during static contraction but were dramatically attenuated or reversed to suppressive responses during cycling (task-dependent modulation); 2) soleus H-reflexes were larger in the high muscle activation condition but were unaffected by task (no task-dependent modulation). Thus opposite results were obtained in the two reflex pathways. It is concluded that cutaneous and H-reflexes are modulated by different mechanisms during active locomotor-like movements.

Retinoids as ligands and coactivators of protein kinase C alpha

Whereas retinoic acids control nuclear events, a second class of retinol metabolites, that is, the hydroxylated forms exemplified by 14-hydroxy-retro-retinol (HRR), operate primarily in the cytoplasm. They function as regulatory cofactors for cell survival/cell death decisions. In accordance with these biological aspects, we demonstrate that these retinoids bound protein kinase C (PKC) alpha with nanomolar affinity and markedly enhance the activation of PKC alpha and the entire downstream MAP kinase pathway by reactive oxygen species. HRR was 10 times more efficient than retinol, and the optimum doses are 10-7 and 10-6 M, respectively. PKC alpha activation was reversed rapidly by imposition of reducing conditions. The retinoid binding site was mapped to the first cysteine-rich region in the regulatory domain, C1A, yet was distinct from the binding sites of diacylglycerol and phorbol esters. The C1B domain bound retinoids poorly. The emerging theme is that retinoids serve as redox regulators of protein kinase C.

Modulation of human cutaneous reflexes during rhythmic cyclical arm movement

The organization and pattern of cutaneous reflex modulation is unknown during rhythmic cyclical movements of the human upper limbs. On the assumption that these cyclic arm movements are central pattern generator (CPG) driven as has been suggested for leg movements such as walking, we hypothesized that cutaneous reflex amplitude would be independent of electromyographic (EMG) muscle activation level during rhythmic arm movement (phase-dependent modulation, as is often the case in the lower limb during locomotion). EMG was recorded from eight muscles crossing the human shoulder, elbow, and wrist joints while whole arm rhythmic cyclical movements were performed. Cutaneous reflexes were evoked with trains of electrical stimulation delivered at non-noxious intensities (approximately 2 x threshold for radiating paresthesia) to the superficial radial nerve innervating the lateral portion of the back of the hand. Phasic bursts of rhythmic muscle activity occurred throughout the movement cycle. Rhythmic EMG and kinematic patterns were similar to what has been seen in the human lower limb during locomotor activities such as cycling or walking: there were extensive periods of reciprocal activation of antagonist muscles. For most muscles, cutaneous reflexes were modulated with the movement cycle and were strongly correlated with the movement-related background EMG amplitude. It is concluded that cutaneous reflexes are primarily modulated by the background muscle activity during rhythmic human upper limb movements, with only some muscles showing phase-dependent modulation.

A pilot study of telemedicine for new neurological outpatient referrals

We investigated whether new patients attending a neurological outpatient clinic could be safely managed by neurologists at a distance, using a video-link. In Northern Ireland, a video-link, transmitting at 384 kbit/s, was set up between a neurological centre and a small rural hospital 140 km away. Twenty-five unselected patients who had been referred by their family doctor were assessed by a neurologist using the telemedicine link and then immediately by another neurologist face to face. Examiners were blinded to the results of each other's assessment. In 24 cases the diagnoses made after the telemedicine and face-to-face examinations were identical. There were minor differences between the type and number of investigations requested, and the requirements for treatment and follow-up between the two groups. Disposal method was the same in 21 of the cases. No major organizational difficulties were encountered during the study. The study showed that neurologists can deliver outpatient neurological care to distant patients using telemedicine. This has the potential to allow access to assessment for the large number of neurological outpatients who might otherwise be denied it.

The cysteine-rich regions of the regulatory domains of Raf and protein kinase C as retinoid receptors

Vitamin A and its biologically active derivatives, the retinoids, are recognized as key regulators of vertebrate development, cell growth, and differentiation. Although nuclear receptors have held the attention since their discovery a decade ago, we report here on serine/threonine kinases as a new class of retinoid receptors. The conserved cysteine-rich domain of the NH(2)-terminal regulatory domains of cRaf-1, as well as several select domains of the mammalian protein kinase C (PKC) isoforms alpha, delta, zeta, and mu, the Drosophila and yeast PKCs, were found to bind retinol with nanomolar affinity. The biological significance was revealed in the alternate redox activation pathway of these kinases. Retinol served as a cofactor to augment the activation of both cRaf and PKC alpha by reactive oxygen, whereas the classical receptor-mediated pathway was unaffected by the presence or absence of retinol. We propose that bound retinol, owing to its electron transfer capacity, functions as a tag to enable the efficient and directed redox activation of the cRaf and PKC families of kinases.

The cost-effectiveness of teleneurology consultations for patients admitted to hospitals without neurologists on site. 1: A retrospective comparison of the case-mix and management at two rural hospitals

We are currently evaluating the use of telemedicine for improving the care of patients admitted with neurological symptoms to hospitals that do not have specialist neurologists on site. To do this we have been comparing the outcome of patients admitted to two small hospitals. In one hospital all patients with neurological symptoms are seen by a neurologist at a distance using an interactive video-link transmitting at 384 kbit/s; in the other patients with neurological problems are managed as per usual practices. For the results of this study to be valid, it is essential that the case-mix and process of management for neurological patients are similar at the two hospitals. We therefore compared the case-mix, process of management, and outcome for all patients admitted over a four-month period to either hospital who had been coded using ICD-10 as having a final diagnosis of a neurological condition. No appreciable differences were noted between the two hospitals for measures of case-mix or outcome. Likewise, most measures of process were similar, although there was a significant difference for the overall length of hospital episode between the two hospitals. When patients with prolonged hospital episodes were excluded, or only patients with a diagnosis of headache, epilepsy or transient ischaemic attack were considered (who as a group made up the bulk of neurological admissions), the difference in the length of hospital episode was not significant. It should therefore be possible for us to estimate the effect of telemedicine on the management of patients with neurological problems.

The utilization of visual information in the control of rapid sequential aiming movements

Two experiments were conducted to examine the role of vision in the execution of a movement sequence. Experiment 1 investigated whether individual components of a sequential movement are controlled together or separately. Participants executed a rapid aiming movement to two targets in sequence. A full vision condition was compared to a condition in which vision was eliminated while in contact with the first target. The size of the first target was constant, while the second target size was varied. Target size had an influence on movement time and peak velocity to the first target. Vision condition and target size did not affect the time spent on the first target. These results suggest that preparation of the second movement is completed before the first movement is terminated. Experiment 2 examined when this preparation occurred. A full vision condition was compared to a condition in which vision was occluded during the flight phase of the first movement. Movement initiation times were shorter when vision was continually available. Total movement time was reduced with vision in two-target condition, but not in a control one-target condition. The time spent on the first target was greater when vision was not available during the first movement component. The results indicate that vision prior to movement onset can be used to formulate a movement plan to both targets in the sequence [Fischman & Reeve (1992).

Molecular characterization of a nosocomial outbreak of human respiratory syncytial virus on an adult leukemia/lymphoma ward

Although nosocomial transmission of human respiratory syncytial virus (HRSV) and its effect on morbidity and mortality among immunocompromised adults are well recognized, few studies have applied molecular techniques to differentiate nosocomial from community-acquired infections. Between January and April 1997, an outbreak of HRSV occurred among adult patients in a leukemia/lymphoma ward. Among 45 hospitalized patients undergoing bronchoscopy for investigation of acute respiratory illness, 8 were identified with HRSV infection. One infected patient developed symptoms before admission and was thought to be the index case. However, subsequent sequencing of 7 HRSV isolates identified 2 distinct genotypes, GA5 (1 case) and GB3 (6 cases). The 6 GB3 isolates could be further differentiated into 2 strains with identical nucleotide sequences that differed from each other and from 14 community HRSV isolates. Instead of a single nosocomial outbreak of HRSV, multiple introductions of HRSV likely occurred with distinct lines of nosocomial transmission.

Changes in posture alter the attentional demands of voluntary movement

Two simple experiments reveal that the ease with which an action is performed by the neuromuscular-skeletal system determines the attentional resources devoted to the movement. Participants were required to perform a primary task, consisting of rhythmic flexion and extension movements of the index finger, while being paced by an auditory metronome, in one of two modes of coordination: flex on the beat or extend on the beat. Using a classical dual-task methodology, we demonstrated that the time taken to react to an unpredictable visual probe stimulus (the secondary task) by means of a pedal response was greater when the extension phase of the finger movement sequence was made on the beat of the metronome than when the flexion phase was coordinated with the beat. In a second experiment, the posture of the wrist was manipulated in order to alter the operating lengths of muscles that flex and extend the index finger. The attentional demands of maintaining the extend-on-the-beat pattern of coordination were altered in a systematic fashion by changes in wrist posture, even though the effector used to respond to the visual probe stimulus was unaffected.

Multicenter comparison of the digene hybrid capture CMV DNA assay (version 2.0), the pp65 antigenemia assay, and cell culture for detection of cytomegalovirus viremia

We compared the Digene Hybrid Capture CMV DNA Assay version 2.0, the pp65 antigenemia assay, traditional tube culture, and shell vial culture for the detection of cytomegalovirus (CMV) viremia in several patient populations at three centers. Of 561 blood specimens collected from 402 patients, complete clinical and laboratory data were available for 489. Using consensus definitions for true positives and true negatives, the sensitivities of the Hybrid Capture assay, antigenemia, shell vial, and tube culture were 95, 94, 43, and 46%, respectively. The specificities of the Hybrid Capture assay and antigenemia were 95 and 94%, respectively. At all three study sites, the detected level of CMV viremia was significantly higher with the Hybrid Capture assay or antigenemia than with shell vial and tube culture. In a group of 131 healthy nonimmunosuppressed volunteers, the Hybrid Capture assay demonstrated a specificity of over 99%. The Hybrid Capture assay is a standardized assay that is simple to perform and can utilize whole blood specimens that have been stored for up to 48 h. The high sensitivity and specificity of the Hybrid Capture assay along with its simplicity and flexibility make it a clinically useful assay for the detection of CMV viremia in immunocompromised or immunosuppressed patients. Further evaluation to determine its role in predicting CMV disease and for monitoring the therapeutic response to anti-CMV therapy is needed.

The clinical utility of CMV surveillance cultures and antigenemia following bone marrow transplantation

At our institution, the cytomegalovirus (CMV) prophylaxis protocol for allogeneic bone marrow transplant (BMT) recipients who are CMV-seropositive or receive marrow from a CMV-seropositive donor consists of a surveillance bronchoscopy approximately 35 days posttransplant. Patients with a positive surveillance bronchoscopy for CMV receive pre-emptive ganciclovir. In order to determine the utility of other screening methods for CMV, we prospectively performed weekly CMV antigenemia, and blood, urine and throat cultures from time of engraftment to day 120 post-BMT in 126 consecutive patients. Pre-emptive ganciclovir was given to 11/81 patients (13.6%) because of a positive surveillance bronchoscopy for CMV. Results of CMV blood, urine and throat cultures and the antigenemia assay done prior to or at the time of the surveillance bronchoscopy were analyzed for their ability to predict the bronchoscopy result. The antigenemia test had the highest positive and negative predictive values (72% and 96%, respectively). The ability of these tests to predict CMV disease was evaluated in the 70 patients with a negative surveillance bronchoscopy who did not receive pre-emptive ganciclovir. Of 19 cases of active CMV disease, CMV antigenemia was positive in 15 patients (79%) a mean of 34 days preceding symptoms. Blood cultures were positive in 14/19 patients (74%) a mean of 31 days before onset of disease. CMV antigenemia is useful for predicting the surveillance bronchoscopy result, and also predicts the development of CMV disease in the majority of patients missed by the surveillance bronchoscopy.

Evaluation of the Digene Hybrid Capture System for detection and quantitation of human cytomegalovirus viremia in human immunodeficiency virus-infected patients

The Digene Hybrid Capture System (DHCS) is a solution hybridization antibody capture assay for the chemiluminescent detection and quantitation of cytomegalovirus (CMV) DNA in leukocytes. This assay was compared with the CMV antigenemia assay and shell vial and tube cultures for the detection of CMV in 234 blood specimens from 72 patients with human immunodeficiency virus. Intra- and interrun precision of the DHCS assay gave coefficients of variation of 17.8 and 16.3%, respectively. The correlation coefficient for the quantitative results obtained by the DHCS assay and the antigenemia assay was 0.911 (95% confidence interval, 0.885 to 0.930). Agreement between the DHCS assay and the other three assays ranged from 83 to 86%. The DHCS assay detected 71, 87, and 84% of specimens that were positive by antigenemia, shell vial cultures, and tube culture, respectively. A total of 92% of specimens that were positive by the DHCS assay were also positive by at least one of the other assays. Evaluation of the usefulness of quantitation of CMV DNA by using the DHCS assay and its correlation with clinical disease demonstrated that, with some exceptions, patients with clinical CMV disease tended to have high levels of DNA whereas asymptomatic patients tended to have low or undetectable levels. Overall, the DHCS assay provided a rapid, quantitative, and objective measure of CMV activity in leukocytes, but results did not always correlate with clinical disease.

A mucopyocele of the clivus: case report

OBJECTIVE AND IMPORTANCE

There are increasing reports of nasal sinus mucopyoceles eroding the base of the cranium and causing the rapid onset of neurological complications. Uncommon presentations can mimic tumors, but the infectious nature mandates an urgent surgical decompression. It is important to document these uncommon presentations. CLINICIAL PRESENTATION: A mucopyocele of the clivus is reported in a patient with a frequent history of sinusitis. Diplopia caused by an acute sixth nerve palsy prompted the radiological diagnosis with computed tomography and magnetic resonance imaging.

INTERVENTION

Transsphenoidal drainage of the lesion lead to marked improvement in the patient.

CONCLUSION

This is the third reported case of a clival mucocele. Mucoceles of nasal sinuses can erode intracranially, causing neurological sequalae, and clival involvement is extremely rare. Early drainage leads to marked improvement.

Retro-retinoids in regulated cell growth and death

Vitamin A serves as a prohormone from which three classes of active metabolites are derived: the aldehydes, the carboxylic acids, and the retro-retinoids. Although these three classes are united under the rubric of signal transduction, they act by different molecular mechanisms: the 11-cis-retinaldehydes combine with opsin to form the universal visual pigments and the retinoic acids form ligands for transcription factors, whereas the retro-retinoids, as shown here, intersect with signal transduction at a cytoplasmic or membrane site. The retro-retinoid, anhydroretinol (AR), has long been known to act as a growth inhibitor in lymphocytes, whereas 14-hydroxy-4,14-retro-retinol (14-HRR) is required for normal lymphocyte proliferation. A mutually reversible relationship exists between these two retro-retinoids as one can reverse the effects of the other when given in pharmacological doses. The common explanation for reversible inhibition is competition for a shared receptor. We now provide evidence that when AR is given to T cells unmitigated by 14-HRR, rapid cell death can occur. The circumstances are closely related to nonclassical forms of apoptosis: within 2 h of AR administration the T cells undergo widespread morphological changes, notably surface blebbing and ballooning and, inevitably, bursting. In contrast, nuclear changes are comparatively mild, as indicated by absence of chromatin condensation and overt DNA cleavage to discrete nucleosomal fragments, although DNA nicks are readily discernible by terminal deoxynucleotidyl transferase assay. What further distinguishes the AR-induced form of apoptosis from classical ones is a lack of requirements of messenger RNA and protein synthesis, suggesting that the events leading to cell death are primarily initiated and play themselves out in the cytoplasm. This view is further reinforced by the finding that herbimycin A can prevent the onset of programmed cell death. The importance of our findings is that they strongly suggest a second messenger role for vitamin A metabolites in the cytoplasmic realm that has not been seen previously. These findings are entirely compatible with a general notion that in a cell requiring multiple coordinated signals for survival, the provision of an unbalanced signal can initiate programmed cell death. Collectively, our data also challenge the paradigm that retinoids (outside vision) solely mediate their function via the steroid/ retinoic acid receptor family of nuclear transcription factors. Instead, a mode of action in the cytoplasmic realm akin to one attributed to other small lipophilic second messenger molecules, such as diacyl glycerol or ceramide, may apply to retro-retinoids.

The influence of target perturbation on manual aiming asymmetries in right-handers

Ten right-handed subjects performed 100 target-aiming movements with each hand. These movements were directed toward a small target on the midline. On 60% of the trials, the target remained stationary. On other randomly placed trials, the target "jumped" to a location 3 cm to the right (20%) or left (20%) of its original position when the cursor had travelled 6.5 cm. Although no hand differences were evident in the control condition, the right hand acquired the new target location more quickly than the left hand when the target was perturbed in either direction. Kinematic data revealed that this advantage was not due to initiating an adjustment to the initial movement more rapidly, but rather less time decelerating the corrective movement. Movement adjustments on perturbed trials were implemented more rapidly in left space than right space independent of the hand doing the aiming. These asymmetries may reflect the differential role of the two cerebral hemispheres in the control of goal-directed movements.