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From stochastic single atomic switch to nanoscale resistive memory device

NANOSCALE 2011年第4期3卷 1504-1507页

作者： Geresdi, Attila Halbritter, Andras Gyenis, Andras Makk, Peter Mihaly, Gyoergy Budapest Univ Technol & Econ Dept Phys H-1111 Budapest Hungary Hungarian Acad Sci Condensed Matter Res Grp H-1111 Budapest Hungary

We study the switching characteristics of nanoscale junctions created between a tungsten tip and a silver film covered by a thin ionic conductor layer. Atomic-sized junctions show spectacular current induced switching characteristics, but both the magnitude of the switching voltage and the direction of the switching vary randomly for different junctions. In contrast, somewhat larger junctions with diameters of a few nanometres display a well defined, reproducible switching behavior attributed to the formation and destruction of nanoscale channels in the ionic conductor surface layer. Our results define a lower size limit of 3 nm for reliable ionic nano-switches, which is well below the resolution of recent lithographic techniques.

关键词： Electric Conductivity Electric Conductivity Equipment Design Equipment Failure Analysis Microelectrodes Nanotechnology/instrumentation signal processing, computer-assisted/instrumentation Silver/chemistry Stochastic Processes

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A novel logic switch based on individual ZnO nanotetrapods

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NANOSCALE 2011年第5期3卷 2166-2168页

作者： Sun, Kai Qi, Junjie Zhang, Qi Yang, Ya Zhang, Yue Univ Sci & Technol Beijing State Key Lab Adv Met & Mat Sch Mat Sci & Engn Beijing 100083 Peoples R China Univ Sci & Technol Beijing Key Lab New Energy Mat & Technol Beijing 100083 Peoples R China

Logic switch based on individual ZnO nanotetrapods was designed and the electromechanical properties were in situ investigated using scanning electron microscopy. The current through two adjacent legs of the tetrapod can be tuned by applying force on the leg that is perpendicular to the substrate. By applying a pulse force on the leg, this device revealed a good sensitivity and an on/off ratio of 1.14 was achieved. The piezoelectric electrical field at the root of the nanotetrapod may contribute to these logic devices, and logic states depend on the direction of built-in potential induced by piezoelectricity and the source-drain current direction.

关键词： Equipment Design Equipment Failure Analysis Micro-Electrical-Mechanical Systems/instrumentation Nanostructures/chemistry Nanostructures/ultrastructure Nanotechnology/instrumentation Particle Size signal processing, computer-assisted/instrumentation Stress, Mechanical Zinc Oxide/chemistry

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THE INTEGRITY OF VISUAL-PROPRIOCEPTIVE MAPPING IN CEREBRAL-PALSY

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NEUROPSYCHOLOGIA 1991年第11期29卷 1095-1106页

作者： WANN, JP EDINBURGH CTR RES CHILD DEV EDINBURGHSCOTLAND

Existing data on the ability of normal children to make intra-modal and cross-modal judgements about limb position are reviewed. A pattern of results emerges which suggests that although young children have difficulty with proprioceptive judgements. their performance is significantly enhanced if the task involves matching vision against proprioception. Some preliminary findings with cerebral palsied children suggest that this advantage may sometimes be lost. It is suggested. however, that the tasks used in previous studies do not allow the precise appraisal of this ability. This study examined intra- and cross-modal judgements in eight normal adults and eight severely cerebral palsied adolescents. In addition to the usual measures of spatial accuracy, joint angle measurements were recorded which allow some appraisal of the information strategy used for respective tasks. The results suggest that the cerebral palsied students had specific problems with mapping between vision and proprioception. This is discussed from a perspective of whether such mapping requires adaptive behaviour within a stable explorative environment, which is disrupted in cases of severe cerebral palsy.

关键词： Adolescent Biofeedback, Psychology/instrumentation Cerebral Palsy/psychology Cerebral Palsy/rehabilitation Child Humans Kinesthesis Neurologic Examination/instrumentation Paraplegia/psychology Paraplegia/rehabilitation Proprioception Psychomotor Performance Quadriplegia/psychology Quadriplegia/rehabilitation signal processing, computer-assisted/instrumentation Visual Perception

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Noninvasive evaluation of arterial abnormalities in young patients with neurofibromatosis type 1

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ANGIOLOGY 2000年第9期51卷 733-741页

作者： Tedesco, MA Ratti, G Di Salvo, G Martiniello, AR Limongelli, G Grieco, M Calabrese, E Grassia, C Iacono, A Lama, G Univ Naples 2 Med Surg Inst Cardiol I-80136 Naples Italy Univ Naples 2 Dept Pediat I-80136 Naples Italy

Neurofibromatosis regroups at least two different autosomal dominant genetic disorders: neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). Vascular disease is an underestimated complication of NF1. Few studies are available on this, all based on case reports. Neurofibromin, NF1 protein product, has also been detected in aortic smooth muscle. The purpose of this study was to evaluate the physical properties of the vessels, by measuring the carotid-femoral pulse wave velocity (PWV). This parameter was assessed by the Complior(R), a new noninvasive, validated device, used to screen a large population. The authors studied 64 neurofibromatosis patients (34 boys and 30 girls) with a mean age of 12 years (range 5-25 years). To investigate the presence of vascular lesions, aortic stiffness was evaluated by carotid-femoral PWV by using an automatic processor (Complior(R)). They compared data from the PWV with a control group (30 healthy children, 17 boys and 13 girls, mean age 11 years, range 5-23 years). The calculated mean PWV in the control group was 6.5 +/- 1.15 m/s. The mean PWV of the 64 young patients with NF1 was 6.3 +/- 1.02 m/s. There was no difference between the two groups (p=0.39). Nevertheless, analysis of the linear regression has shown a linear relationship between systolic blood pressure (SBP) and PWV in the control group, while in NF1 patients this relationship is not present. The authors suggest that the coexistence of different factors, such as intimal proliferation, thinning media, fragmentation of the elastic tissue, irregularity, stenosis and tortuosity of the vessels, dysplasia of the small vessels, that counterbalance PWV, normalize the mean value. They emphasize the importance of a careful vascular evaluation, using noninvasive method, such as Complior(R). This device is well accepted by NF1 patients.

关键词： Adolescent Adult Blood Flow Velocity/genetics Blood Flow Velocity/physiology Blood Pressure/genetics Blood Pressure/physiology Child Child, Preschool Elasticity Female Gene Expression Regulation, Neoplastic/physiology Genetic Screening Humans Male Muscle, Smooth, Vascular/physiopathology Nerve Tissue Proteins/genetics Neurofibromatosis 1/diagnosis Neurofibromatosis 1/genetics Neurofibromatosis 1/physiopathology Neurofibromin 1 Pulsatile Flow/genetics Pulsatile Flow/physiology Reference Values signal processing, computer-assisted/instrumentation Tunica Intima/physiopathology Vascular Diseases/diagnosis Vascular Diseases/genetics Vascular Diseases/physiopathology

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SCREENING FOR SUBCLINICAL SLEEP-DISORDERED BREATHING

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SLEEP 1990年第4期13卷 344-353页

作者： SCHARF, SM GARSHICK, E BROWN, R TISHLER, PV TOSTESON, T MCCARLEY, R VET ADM MED CTR W ROXBURY DIV PULM MED SERV BOSTON MA 02132 USA VET ADM MED CTR W ROXBURY DIV PULM PSYCHIAT SERV BOSTON MA 02132 USA BRIGHAM & WOMENS HOSP CHANNING LAB BOSTON MA 02115 USA HARVARD UNIV SCH MED BOSTON MA 02115 USA

We evaluated self-administered questionnaires and short sleep studies in screening for sleep-disordered breathing (SDB) in 40 hypertensive men ages 36-66 unselected for symptoms. Each subject completed a questionnaire including questions on sleep-related symptoms and underwent overnight polysomnography in which we evaluated the apnea-hypopnea index (AHI) and the percentage of time during which arterial O2 saturation was < 90% (T90). The first 90 min of overnight study was evaluated separately, and 10 subjects with an AHI .gtoreq. 10 also underwent late afternoon nap study. By overnight polysomnography, 48% of the cohort had an AHI .gtoreq. 10, and 35% had a T90 .gtoreq. 10%. Using linear regression, we found no features of the symptom questionnaire that strongly predicted AHI. Only self-reported snoring and baseline arterial Po2 significantly predicted T90. The AHI and T90 were not significantly correlated. Considering an AHI .gtoreq. 10 in the overnight study as "abnormal" and an AHI .gtoreq. 10 on the short study as a "positive" test, the specificity of the AHI in the first 90 min was 100% (21/21), and the sensitivity was 42% (8/19). The sensitivity of the nap study was 60% (6/10). We conclude that in a cohort unselected for symptoms, the ability of self-administered questionnaires to predict SDB was low;short studies were only moderately sensitive for detecting an AHI .gtoreq. 10, and the AHI was not a major determinant of nocturnal desaturation.

关键词： Adult Aged Cohort Studies Humans Hypertension/complications Male Mass Screening Microcomputers Middle Aged Monitoring, Physiologic/instrumentation Risk Factors signal processing, computer-assisted/instrumentation Sleep Apnea Syndromes/diagnosis Sleep Apnea Syndromes/prevention & control

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POLYSOMNOGRAPHIC ASSESSMENT OF DIMS - EMPIRICAL-EVALUATION OF ITS DIAGNOSTIC-VALUE

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SLEEP 1989年第4期12卷 315-322页

作者： EDINGER, JD HOELSCHER, TJ WEBB, MD MARSH, GR RADTKE, RA ERWIN, CW DUKE UNIV MED CTR CTR SLEEP DISORDERS DURHAM NC 27710 USA

This investigation examined the diagnostic value of polysomnography (PSG) for evaluating disorders of initiating and maintaining sleep (DIMS). The sample consisted of 100 outpatients who presented to the Duke Sleep Disorders Center with a complaint of chronic insomnia. All patients were given comprehensive medical, psychiatric, behavioral, and ambulatory PSG evaluations. Sleep disorder diagnoses were assigned using the criteria of the Association of Sleep Disorders Centers. Overall, PSG yielded important diagnostic information in 65% of the sample: 34% were given a primary sleep disorder diagnosis that was heavily dependent on PSG data [periodic movements of sleep (PMS) = 25%, apnea = 3%, and subjective insomnia = 6%];15% were given a secondary diagnosis of one of these disorders;and PSG ruled out suspected PMS in 9% and sleep apnea in 7% of the sample. Patients >40 years of age had a significantly higher rate of positive PSG findings than younger patients. Using only the clinical exam, two experienced sleep clinicians were able to predict only 14 of 25 PMS cases and one of three cases of sleep apnea. Based on these data, we suggest using PSG routinely with older insomniacs and with younger patients who fail initial treament.

关键词： Adult Aged Aged, 80 and over Alcoholism/complications Alcoholism/complications Arousal Electroencephalography/instrumentation Female Humans Male Mental Disorders/complications Middle Aged Monitoring, Physiologic/instrumentation signal processing, computer-assisted/instrumentation Sleep Apnea Syndromes/diagnosis Sleep Initiation and Maintenance Disorders/diagnosis Substance-Related Disorders/complications Substance-Related Disorders/complications

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Synthesis of single crystalline CdS nanocombs and their application in photo-sensitive field emission switches

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NANOSCALE 2011年第3期3卷 1078-1083页

作者： Chavan, Padmakar G. Badadhe, Satish S. Mulla, Imtiaz S. More, Mahendra A. Joag, Dilip S. Univ Pune Dept Phys Ctr Adv Studies Mat Sci & Condensed Matter Phys Pune 411007 Maharashtra India Natl Chem Lab Phys & Mat Chem Div Pune 411008 Maharashtra India

Single crystalline CdS nanocombs were synthesized by a thermal evaporation route. The photo-sensitive field emission current shows a reproducible switching behavior, with a rise in current level of nearly five times the initial preset value of similar to 1 mu A. An ultra low turn-on field, required to draw an emission current density of similar to 0.1 mu A cm(-2) (100 nA), is found to be similar to 0.26 V mu m(-1) (260 V), which is much lower than the reported values for various other CdS nanostructures. Upon illumination with visible light the CdS nanocombs act as a photo field emission switch. At an applied field of similar to 0.65 V mu m(-1) the current densities are observed to be similar to 14.6 mu A cm(-2) and similar to 26.9 mu A cm(-2), without and with light illumination, respectively. The average emission current is seen to be stable over the duration of measurement for two preset values. The high sensitivity and fast response in the visible range indicates that the CdS nanocombs can be used as a photo-sensitive field emitting switch in device applications, and also in pulsed electron beam technology.

关键词： Cadmium Compounds/chemistry Cadmium Compounds/radiation effects Equipment Design Equipment Failure Analysis Light Light Materials Testing Nanostructures/chemistry Nanostructures/radiation effects Nanostructures/ultrastructure Photometry/instrumentation signal processing, computer-assisted/instrumentation Sulfides/chemistry Sulfides/radiation effects

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COMPARISON BETWEEN THE RESULTS OF AN AUTOMATIC AND A VISUAL SCORING OF SLEEP EEG RECORDINGS

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SLEEP 1989年第4期12卷 354-362页

作者： FERRI, R FERRI, P COLOGNOLA, RM PETRELLA, MA MUSUMECI, SA BERGONZI, P UNIV CAGLIARI CATTEDRA NEUROPATOL & PSICOPATOL I-09100 CAGLIARI ITALY

In this paper, results from the visual scoring of nocturnal polygraphic recordings, carried out by nine different groups of readers from different Italian sleep laboratories, are analyzed;inter- and intragroup variability is shown and statistically discussed. Data are then compared with the results of an automatic scoring of the same recordings, carried out by the Medilog Sleep Stager. The validity of this automatic method of scoring is discussed. Finally, an epoch by epoch analysis is described, with the aim of achieving a more detailed evaluation of the intergroup variability.

关键词： Adolescent Adult Cerebral Cortex/physiology Electroencephalography/instrumentation Evoked Potentials Female Humans Male signal processing, computer-assisted/instrumentation Sleep Stages/physiology Sleep, REM/physiology Software Wakefulness/physiology

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FAST MULTISITE OPTICAL-RECORDING OF MONOSYNAPTIC AND POLYSYNAPTIC ACTIVITY IN THE HAMSTER SUPRACHIASMATIC NUCLEUS EVOKED BY RETINOHYPOTHALAMIC TRACT STIMULATION

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NEUROIMAGE 1994年第4期1卷 247-263页

作者： SENSEMAN, DM REA, MA ARMSTRONG LAB BRAIN RES INSTBROOKS AFBTX 78235

Responses of the hamster suprachiasmatic nucleus (SCN) to retinohypothalamic tract (RHT) stimulation were studied in horizontal hypothalamic slices using fast multisite optical recording techniques. A 124-element photodiode detector array provided high-speed monitoring (0.5 ms/frame) of evoked neural activity in the SCN, while a larger 464-element photodiode array yielded improved spatial imaging with some loss in temporal resolution (1.6 ms/frame). Brief electrical stimulation of the optic nerves evoked a propagated compound action potential that was recorded optically as a single transient deplorization in many slice regions, including the SCN. Only within the SCN, however, was this optic tract signal followed by additional voltage-dependent optical responses which exhibited a fast and a slow depolarizing component. The initial upstroke of the fast component was Ca2+-insensitive and is presumed to reflect activity in presynaptic RHT afferents. The remainder of the fast depolarization and the slow depolarization were Ca2+-sensitive. These responses were labeled the early population excitatory postsynaptic potential (Early P.E.P.S.P.) and the Late P.E.P.S.P. respectively. The Late P.E.P.S.P. was not enhanced by K+ channel blockade, suggesting that glial depolarization is not the primary source of this component. Drugs known to suppress RHT-evoked SCN field potentials also suppressed the Early and Late P.E.P.S.P.'s recorded optically in the SCN. Unexpectedly, the Early P.E.P.S.P. was also reduced by the GABA(A) antagonist, bicuculline. Surface plots of normalized peak amplitudes showed that both SCN components had similar spatial distributions within the SCN, although the Early P.E.P.S.P. tended to be slightly more prominent within the medial SCN in some preparations. It is suggested that the Early P.E.P.S.P. represents firing of monosynaptically activated SCN neurons, while the Late P.E.P.S.P. reflects polysynaptic activity within the intrinsic SCN neuronal network

关键词： Animals Automatic Data processing Brain Mapping/instrumentation Brain Mapping/instrumentation Circadian Rhythm/physiology computer Systems Cricetinae Electric Stimulation/instrumentation Electroencephalography/instrumentation Hypothalamus/physiology Light Light Male Mesocricetus Nerve Net/physiology Retina/physiology signal processing, computer-assisted/instrumentation Suprachiasmatic Nucleus/physiology Synapses/physiology Synaptic Transmission/physiology Visual Pathways/physiology

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SLEEP AND WAKEFULNESS IN NORMAL PREADOLESCENT CHILDREN

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SLEEP 1989年第4期12卷 299-308页

作者： PALM, L PERSSON, E ELMQVIST, D BLENNOW, G UNIV LUND HOSP DEPT CLIN NEUROPHYSIOL S-22185 LUND SWEDEN

Eighteen healthy children, 9 boys and 9 girls, between 8 and 12 years of age were examined with polygraphic sleep records, multiple sleep latency tests (MSLTs), and measurements of reaction times. Sleep was recorded at home on Oxford Medilog 9 channel cassette tape recorders (Oxford Medical Systems, Abingdon, U.K.) and sleep staging was performed from the screen of the display unit. Two consecutive nights were recorded. MSLT was done in the laboratory. The subjects were given 30 min to fall asleep on four occasions during the day after the last recorded night of sleep. Reaction times were measured repeatedly between each MSLT trial. More slow wave sleep was found in this study compared to others. Also, the first night effect was slight. It is proposed that this is due to the fact that the recordings were performed at home. The initial sleep cycle was incomplete in almost all subjects. A sleep stage with traits of both rapid eye movement (REM) and nonREM could be seen in this cycle, probably representing an abortive REM period. MSLT confirmed the low daytime sleepiness in healthy preadolescent children. A sleep latency of 10 min or less on two or more sleep trials, or a daily mean sleep latency of less than 20 min, is rarely seen in this age group. The reaction times were within normal limits for the age of the subjects. Nighttime sleep values, daytime sleep latencies, and reaction times were not correlated in these normal-sleeping children.

关键词： Arousal/physiology Cerebral Cortex/physiology Child Child Development Electroencephalography/instrumentation Humans Monitoring, Physiologic/instrumentation Reaction Time/physiology Reference Values signal processing, computer-assisted/instrumentation Sleep Stages/physiology Sleep, REM/physiology Wakefulness/physiology

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