Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.

We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0±0.3 meV/atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

Optical measurement of the effect of electric fields on the nuclear spin coherence of rare-earth ions in solids.

We show that the coherence properties of the nuclear spin states of rare-earth ions in solids can be manipulated by small applied electric fields. This was done by measuring the Stark effect on the nuclear quadrupole transitions of (151)Eu in Y(2)SiO(5) (YSO) using a combination of Raman heterodyne optical detection and Stark modulated quadrupole echoes to achieve high sensitivity. The measured Stark coefficients were 0.42 and 1.0 Hz cm/V for the two quadrupole transitions at 34.54 and 46.20 MHz, respectively. The long decoherence time of the nuclear spin states (25 ms) allowed us to make the measurements in very low electric fields of ∼ 10 V/cm, which produced 100% modulation of the nuclear spin echo, and to measure Stark shifts of ∼ 1 Hz or 20 ppm of the inhomogeneous linewidth.

Optical decoherence in eR3+-doped silicate fiber: evidence for coupled spin-elastic tunneling systems.

We measured the optical decoherence times T2, or, equivalently, the homogeneous line width, in an Er-doped optical fiber at low temperature as a function of external magnetic field and temperature using two-pulse photon echoes. The decoherence times were up to 230 ns at fields above 3 T. The magnitude of the line narrowing induced by a magnetic field of 3 T is 2.5 MHz, which is anomalously large compared to that typical for oxide crystals with similar Er3+ concentration. This is interpreted as evidence for dephasing by coupled spin-elastic tunneling modes where the normal glass tunneling modes acquire a magnetic character by coupling to the Er3+ spin.

Highly spin-polarized room-temperature tunnel injector for semiconductor spintronics using MgO(100).

The spin polarization of current injected into GaAs from a CoFe/MgO(100) tunnel injector is inferred from the electroluminescence polarization from GaAs/AlGaAs quantum well detectors. The polarization reaches 57% at 100 K and 47% at 290 K in a 5 T perpendicular magnetic field. Taking into account the field dependence of the luminescence polarization, the spin injection efficiency is at least 52% at 100 K, and 32% at 290 K. We find a nonmonotonic temperature dependence of the polarization which can be attributed to spin relaxation in the quantum well detectors.

Validation of a system of foot ulcer classification in diabetes mellitus.

OBJECTIVE: The lack of a simple, robust classification of diabetic foot ulcers has critically hampered research into optimum patterns of care. We have therefore attempted validation of the previously published S(AD) SAD system, which is based on grading of ulcer features using simple clinical methods. RESEARCH DESIGN AND METHODS: This was a prospective study in which 300 people with ulcers newly referred to a hospital-based multidisciplinary clinic between 1 January 2000 and 1 July 2002 were classified at the time of their first assessment. If a patient had more than one episode, the last to occur was selected as the index ulcer. If two or more ulcers were registered simultaneously, the one which was regarded as the more significant was chosen. Ulcers were categorized according to area, depth, sepsis, ischaemia and neuropathy. All patients were followed for at least 6 months, or until death if earlier. Outcome criteria used were healed and unhealed (unhealed persisting, unhealed at amputation or death) and were cross-tabulated with different baseline variables. RESULTS: Ulcers healed in 209 of the 300 patients (69.7%), while 30.0 (10%) had been resolved by amputation (eight major; 22 minor) and 32 (10.7%) by death. Twenty-nine (9.7%) persisted unhealed. There were significant differences in outcome according to area (chi2=25.9, P < 0.001), depth (chi2=33.8, P < 0.001), sepsis (chi2=13.5, P = 0.004) and arteriopathy (chi2 = 33.7, P < 0.001), but not to denervation (chi2=5.1, P = 0.16). The strength of these associations was confirmed using Somers d: area (rs= -0.24, P < 0.001), depth (rs= -0.32, P < 0.001), sepsis (rs= -0.15, P < 0.01), arteriopathy (rs= -0.30, P < 0.001), denervation (rs= -0.10, P = 0.08). Logistic regression analysis using area, depth, sepsis and arteriopathy as independent variables, and those which contributed significantly to the model were area (P = 0.01), depth (P < 0.001) and arteriopathy (P < 0.001). CONCLUSIONS: These data demonstrate that simple clinical methods can be used to categorize features of individual ulcers, and that area, depth and arteriopathy contribute independently to a model to predict outcome. A system of classification such as this is an essential requirement for the categorization of populations with similar features and similar prognosis, which may then be used as the basis for prospective research into optimal wound management.

Symptoms, signs, and prescribing for acute lower respiratory tract illness.

BACKGROUND: Most patients who consult with acute lower respiratory symptoms receive antibiotics, usually without evidence of significant infection. The physical signs at presentation of acute lower respiratory tract illness and the rate at which symptoms resolve and normal activities recover is not well documented. AIM: To examine in patients with lower respiratory tract infection (LRTi), their physical signs at presentation, their relationship to antibiotic prescribing, and symptom resolution and resumption of normal activities. DESIGN OF STUDY: Analysis of data collected prospectively during presentation of acute LRTi in primary care and from patient symptom diary cards. SETTING: Forty GPs who were members of an informal Community Respiratory Infection Interest Group recruited 391 patients to the study. METHOD: Information was collected on pulse, oral temperature, respiratory rate, abnormalities on auscultation, and details of any antibiotic prescription. Patients completed symptom diary cards for the following 10 days. RESULTS: Of the 391 patients who consulted 71% received antibiotics. A minority had abnormal physical signs: 17% had a pulse greater than 90 bpm, 15% a respiratory rate greater than 20 breaths per minute, 4% had a temperature greater than 38 degrees C, and 25% had an abnormality on auscultation. Antibiotic prescribing was more common in the presence of abnormal chest signs (odds ratio = 8.71, 95% confidence interval = 3.69-20.61) or discoloured sputum (OR = 2.67, 95% CI = 1.57-4.56). Ten days after consultation, 58% of patients were still coughing and 29% had not returned to normal activities. CONCLUSION: Abnormal physical signs at presentation do not explain the high rates of antibiotic prescribing nor do they predict persisting cough and functional impairment at 10 days. Reconsultation for the same symptoms within a month is common and is strongly related to persisting cough, but not abnormalities at presentation.

Two-Color Holographic Recording Scheme Allowing Nonvolatile Reading in Mn:YAlO(3).

We propose and experimentally realize the recording of two-color holographic gratings in Mn:YAlO(3), a potential material for holographic data storage. This type of recording allows for nonvolatile retrieval of recorded information at the recording wavelength. We demonstrate two-color recording and readout of a 256 x 256 pixel page using red and green laser beams with a bit error rate of 6 x 10(-7).

Spectral hole burning in thulium-doped glass ceramics.

We have used spectral hole burning to measure the homogeneous linewidth of the (3)H(6)(1)- (3)F(3)(1) transition of Tm(3+) ions doped into oxyfluoride glass ceramics consisting of nanocrystals of LaF(3) in an aluminosilicate glass matrix. From the magnitude of the hole width in the nanocrystals and its dependence on temperature, we propose that excitation of tunneling modes in the adjacent glassy phase as well as of confined mechanical modes in the nanocrystals is responsible for the broadening.

Volume holographic data storage at an areal density of 250 gigapixels/in.(2).

One thousand volume holographic data pages, each containing 1x10(6)pixels , are stored in a common volume of LiNbO(3) :Fe by use of the 90 degrees geometry. An effective transverse aperture of 1.6 mm x 1.6mm , realized by repetition of this experiment at each of the eight surrounding locations, results in a demonstrated areal density of 394pixels/mum (2) (254 Gpixels/in. (2)) . Short-focal-length Fourier optics provide a tightly confined object beam at the crystal; the reference beam is angle multiplexed. Data pages retrieved with a 1024 x 1024 CCD camera are processed to remap bad spatial light modulator pixels and to compensate for global and local pixel misregistration and are then decoded with a strong 8-bits-from-12-pixels modulation code. The worst-case raw bit-error rate (BER) before error correction was 1.1x10(-3) , sufficient to deliver a user BER of 10(-12) at an overall code rate of 0.61 user bits per detector pixel. This result corresponds to 1.08% of the well-known theoretical volumetric density limit of 1/lambda(3) .

Demonstration of real-time address header decoding for optical data routing at 1536nm.

We have demonstrated real-time decoding of 20-bit biphase-coded address header pulses, using stimulated photon echoes in a phase-matched crossed-beam configuration. This decoding is one of the functions required for coherent transient optical data routing, packet switching, and processing. The active medium used was single-crystal Y(2)SiO(5) doped with Er(3+), which provides an operating wavelength of 1536 nm.

Experimental study of the effects of a six-level phase mask on a digital holographic storage system.

We measure the M/# and the bit-error rate of a digital holographic storage system with a 4f optical arrangement for three configurations: recording at the Fourier plane with and without a phase mask and recording outside the Fourier plane without a phase mask. Unexpectedly, no significant change in the dynamic range was observed when a phase mask was used to record in thick crystals. However, we show that a phase mask is a key component in a 4f digital holographic storage system if high-fidelity holograms with optimum volumetric density are to be stored.

Factors contributing to the presentation of diabetic foot ulcers.

We have undertaken a prospective study of the presentation of all 669 ulcers seen in a specialist multidisciplinary foot clinic between 1 January 1993 and 1 August 1996, with particular reference to the factors which precipitated ulceration as well as to any delays in referral. Nearly two-thirds (61.3%) of all lesions were first detected by the patient or a relative, and the remainder by a healthcare professional. The median (range) time which elapsed between ulcer onset and first professional review was 4 (0-247) days, and the median time between first review and first referral to the specialist clinic was 15 (0-608) days. Significant delays were judged to have occurred in 39 instances. The most common precipitant of ulceration was rubbing from footwear, which was responsible for 138 (20.6%). Fifty-eight (8.7%) were the result of immobilization from other illness, and a further 24 were the consequence of surgery. Overall, professional factors contributed to the development or deterioration of 106 lesions (15.8% total). These results should form the basis of strategies designed to minimize the onset of ulceration in those known to be at risk: educational strategies need to be directed at professionals as much as at patients.

Conservative management of osteomyelitis in the feet of diabetic patients.

Experience of conservative management of osteomyelitis in a specialized, multidisciplinary, diabetic foot clinic was reviewed. The records of all patients attending the clinic over a 10-year period were examined retrospectively, and 22 patients with overt osteomyelitis were identified. Median age was 66 (31-87) years. In 12 cases the bone infection was a complication of a pre-existing ulcer; the most prevalent organism cultured from swabs was Staphylococcus aureus. The main site of infection was the first toe. The total duration of antibiotic treatment was 12 weeks (median, range 5-72), and clindamycin was the most commonly used oral agent. Four patients did not respond to initial conservative therapy and proceeded to amputation, while 1 patient responded clinically but had a recurrence of osteomyelitis at the same site 6 years later. In the remaining 17 patients resolution of osteomyelitis was achieved with conservative management over a median period of follow-up of 27 (range 5-73) months. The success of conservative therapy with prolonged courses of oral antibiotics challenges conventional advice that excision of infected bone is essential in the management of osteomyelitis affecting the foot in diabetes.

Measurement of photon echoes in ErY(2)SiO(5) at 1.5 microm with a diode laser and an amplifier.

We have measured the optical dephasing time of Er(3+) transitions near 1.5 microm in the two crystallographically inequivalent sites of Y(2)SiO(5), using an external-cavity diode laser amplified by an erbium-doped fiber amplifier. Two-pulse photon echoes were observed at zero field and in magnetic fields up to 55kG, with dephasing times as long as 580 micros (corresponding to a linewidth of 550 Hz). Stimulated echoes were also measured and showed evidence of spectral diffusion during the 13-ms lifetime of the (4)I(13/2) level.

Observation of coherent transients by use of current switching of a semiconductor diode laser.

We have observed optical free induction decay on the (3)H(6)(1) ? (3)H(4)(1) transition of Tm(3+) ions in LaF(3), using an external-cavity diode laser. The diode-laser frequency was switched by the application of a current step, and the resulting transient was detected by heterodyne beating with the laser at its new frequency. This provides a simple new way to measure coherent transients. The beat note shows a frequency chirp that gives a real-time measure of the diode-laser frequency. This result is attributed to changes in the laser lattice temperature on the microsecond time scale.

The influence of antibiotics and other factors on reconsultation for acute lower respiratory tract illness in primary care.

BACKGROUND: Antibiotics are prescribed to the majority of patients consulting their general practitioner (GP) for lower respiratory tract illness (LRTi). A common reason for prescription is the belief that antibiotics reduce re-attendance; a motive supported by the high reconsultation rates for this largely self-limiting illness. Information about reconsultation following treatment of LRTi, and the factors that influence it, is scarce. AIM: To explore factors associated with reconsultation after initial management of LRTi. METHOD: Analysis of data collected prospectively during presentation of acute LRTi in primary care. RESULTS: Seventy-six per cent of 518 patients were prescribed antibiotics, and 30% reconsulted for similar symptoms within the next 28 days (29% of those who were given antibiotics and 33% of those who were not). Forty-one per cent of patients who had seen their GP 15 or more times in the previous two years reconsulted, compared with 13% of those who had made fewer than five visits. Reconsultation was more common in patients with a history of underlying disease (38.6% versus 24.3%) and in patients who reported dyspnoea (41.5% versus 24.3%). CONCLUSION: Reconsultation is common in acute LRTi and is associated with a heightened consulting habit prior to the index consultation, the presence of previous ill health, and dyspnoea. It appears not to be influenced by prescribing antibiotics.

Intensity dependence and white-light gating of two-color photorefractive gratings in LiNbO(3).

Photorefractive gratings have been written in Pr:LiNbO(3) by use of a diode laser for writing and of filtered white light (390-520nm) as a gating source. The gating light increases the writing efficiency by more than 3 orders of magnitude, and the two-step writing process provides nondestructive readout. The material sensitivity for two-color writing rises strongly for gating wavelengths near the bandgap and approaches that of Fe-doped lithium niobate at power densities of a few watts per square centimeter. In addition, we show that the dynamic range of the recording process is strongly dependent on the writing intensity.

Pixel-matched holographic data storage with megabit pages.

Digital data-page holograms consisting of 1024 x 1024 arrays of binary pixels have been stored and subsequently retrieved with an optical exposure consistent with a data rate 1 Gbit /s. Each input pixel was precisely registered with a single detector pixel, and a raw bit-error rate as low as 2.4 x 10(-6) was demonstrated with global-threshold detection. To our knowledge, this is the first demonstration of the often-cited goal of holographic data storage of megabit data pages and a gigabit-per-second data rate.

Reducing reconsultations for acute lower respiratory tract illness with an information leaflet: a randomized controlled study of patients in primary care.

BACKGROUND: General practitioners (GPs) prescribe antibiotics to three-quarters of patients who consult with a lower respiratory tract illness (LRTi). In spite of this management, around a quarter of patients reconsult for the same symptoms within a month. AIM: To investigate the impact of providing a simple leaflet regarding the natural history of lower respiratory tract symptoms on reconsultation rates for previously well adults presenting to their GP with an LRTi. METHOD: Seventy-six GPs studied 1014 previously well adults presenting with an illness defined as an LRTi. Management was left to the GP's discretion. Half of the patients were randomly allocated to receive an information leaflet at the end of the consultation, blinded from the GP. The endpoint was reconsultation for the same symptoms within one month. RESULTS: Follow-up data was available for 1006 adults, of whom 182 (18%) reconsulted. Fewer patients who received the leaflet (75/505; 14.9%) returned to the surgery compared with those who did not (107/501; 21.4%; P = 0.007). The same benefit was found for the 723 (72%) adults treated initially with antibiotics; 16% (60/369) in the leaflet group returned compared with 23% (81/354) in the no leaflet group (P = 0.02). CONCLUSION: Informing previously well patients about the natural history of LRTi symptoms is an effective strategy for reducing reconsultations, benefiting the patient and the GP; it is likely to reduce antibiotic prescriptions and future patient consultation habits.

Photon-gated photoconductivity of Pr(3+):YAG.

We have observed photon-gated photoconductivity in Pr:YAG, providing clear evidence for photoionization of the trivalent praseodymium ion in the solid state. Photoionization occurs by two-step absorption from (3)H(4)(1) ? (1)D(2)(1) followed by an excited-state absorption from (1)D(2) to the lowest component of the 4f5d configuration. The excitation spectrum of the photocurrent shows sharp (1)D(2) spectral features, providing unambiguous assignment of the photocurrent.