Fluctuations in Planar Magnetotransport Due to Tilted Dirac Cones in Topological Materials

Fluctuations in planar magnetotransport are ubiquitous in topological HgTe structures, in both tensile (topological insulator) and compressively strained layers (Weyl semimetal phase). We show that the common reason for the fluctuations is the presence of tilted Dirac cones combined with the formation of charge puddles. The origin of the tilted Dirac cones is the mix of the Zeeman term due to the in-plane magnetic field and quadratic contributions to the dispersion relation. We develop a network model that mimics the transport of tilted Dirac fermions in the landscape of charge puddles. The model captures the essential features of the experimental data. It should be relevant for the interpretation of planar magnetotransport in a variety of topological and small band gap materials.

Macroscopic Quantum Tunneling of a Topological Ferromagnet

The recent advent of topological states of matter spawned many significant discoveries. The quantum anomalous Hall (QAH) effect is a prime example due to its potential for applications in quantum metrology, as well as its influence on fundamental research into the underlying topological and magnetic states and into axion electrodynamics. Here, electronic transport studies on a (V,Bi,Sb)₂ Te₃ ferromagnetic topological insulator nanostructure in the QAH regime are presented. This allows access to the dynamics of an individual ferromagnetic domain. The domain size is estimated to be in the 50-100 nm range. Telegraph noise resulting from the magnetization fluctuations of this domain is observed in the Hall signal. Careful analysis of the influence of temperature and external magnetic field on the domain switching statistics provides evidence for quantum tunneling (QT) of magnetization in a macrospin state. This ferromagnetic macrospin is not only the largest magnetic object in which QT is observed, but also the first observation of the effect in a topological state of matter.

Finite Field Transport Response of a Dilute Magnetic Topological Insulator-Based Josephson Junction

Hybrid samples combining superconductors with magnetic topological insulators are a promising platform for exploring exotic new transport physics. We examine a Josephson junction of such a system based on the dilute magnetic topological insulator (Hg,Mn)Te and the type II superconductor MoRe. In the zero and very low field limits, to the best of our knowledge, the device shows, for the first time, an induced supercurrent through a magnetically doped semiconductor, in this case, a topological insulator. At higher fields, a rich and hysteretic magnetoresistance is revealed. Careful analysis shows that the explanation of this behavior can be found in magnetic flux focusing stemming from the Meissner effect in the superconductor, without invoking any role of proximity-induced superconductivity. The phenomena is important because it will ubiquitously coexist with any exotic new physics that may be present in this class of devices.

Scaling of the Quantum Anomalous Hall Effect as an Indicator of Axion Electrodynamics

We report on the scaling behavior of V-doped (Bi,Sb)_{2}Te_{3} samples in the quantum anomalous Hall regime for samples of various thickness. While previous quantum anomalous Hall measurements showed the same scaling as expected from a two-dimensional integer quantum Hall state, we observe a dimensional crossover to three spatial dimensions as a function of layer thickness. In the limit of a sufficiently thick layer, we find scaling behavior matching the flow diagram of two parallel conducting topological surface states of a three-dimensional topological insulator each featuring a fractional shift of 1/2e^{2}/h in the flow diagram Hall conductivity, while we recover the expected integer quantum Hall behavior for thinner layers. This constitutes the observation of a distinct type of quantum anomalous Hall effect, resulting from 1/2e^{2}/h Hall conductance quantization of three-dimensional topological insulator surface states, in an experiment which does not require decomposition of the signal to separate the contribution of two surfaces. This provides a possible experimental link between quantum Hall physics and axion electrodynamics.

Mechanochemical ablation for symptomatic great saphenous vein reflux: A two-year follow-up

Background Several studies have shown comparable early efficacy of mechanochemical ablation to endothermal techniques. The goal of this report was to show if early efficacy is maintained at 24 months. Methods This was a two-year analysis on the efficacy of mechanochemical ablation in patients with symptomatic C2 or more advanced chronic venous disease. Patients with reflux in the great saphenous vein involving the sapheno-femoral junction and no previous venous interventions were included. Demographic information, clinical, and procedural data were collected. The occlusion rate of treated veins was assessed with duplex ultrasound. Patient clinical improvement was assessed by Clinical-Etiology-Anatomy-Pathophysiology (CEAP) class and venous clinical severity score. Results Of the initial 126 patients, there were 65 patients with 24 month follow-up. Of these 65 patients, 70% were female, with a mean age of 70 ± 14 years and an average body mass index (BMI) of BMI of 30.5 ± 6. The mean great saphenous vein diameter in the upper thigh was 7.6 mm and the mean treatment length was 39 cm. Adjunctive treatment of the varicosities was performed in 14% of patients during the procedure. Closure rates were 100% at one week, 98% at three months, 95% at 12 months, and 92% at 24 months. There was one patient with complete and four with partial recanalization ranging from 7 to 12 cm (mean length 9 cm). There was significant improvement in CEAP and venous clinical severity score (P < .001) for all time intervals. Conclusion Early high occlusion rate with mechanochemical ablation is associated with significant clinical improvement which is maintained at 24 months, making it a very good option for the treatment of great saphenous vein incompetence.

Kinetic limitation of chemical ordering in Bi2Te3-x Se x layers grown by molecular beam epitaxy

We study the chemical ordering in Bi2Te3-x Se x grown by molecular beam epitaxy on Si substrates. We produce films in the full composition range from x = 0 to 3, and determine their material properties using energy dispersive x-ray spectroscopy, x-ray diffraction and Raman spectroscopy. By fitting the parameters of a kinetic growth model to these results, we obtain a consistent description of growth at a microscopic level. Our main finding is that despite the incorporation of Se in the central layer being much more probable than that of Te, the formation of a fully ordered Te-Bi-Se-Bi-Te layer is prevented by kinetic of the growth process. Indeed, the Se concentration in the central layer of Bi2Te2Se1 reaches a maximum of only ≈ 75% even under ideal growth conditions. A second finding of our work is that the intensity ratio of the 0 0 12 and 0 0 6 x-ray reflections serves as an experimentally accessible quantitative measure of the degree of ordering in these films.

Mechanochemical ablation for symptomatic great saphenous vein reflux: A two-year follow-up

Background Several studies have shown comparable early efficacy of mechanochemical ablation to endothermal techniques. The goal of this report was to show if early efficacy is maintained at 24 months. Methods This was a two-year analysis on the efficacy of mechanochemical ablation in patients with symptomatic C2 or more advanced chronic venous disease. Patients with reflux in the great saphenous vein involving the sapheno-femoral junction and no previous venous interventions were included. Demographic information, clinical, and procedural data were collected. The occlusion rate of treated veins was assessed with duplex ultrasound. Patient clinical improvement was assessed by Clinical-Etiology-Anatomy-Pathophysiology (CEAP) class and venous clinical severity score. Results Of the initial 126 patients, there were 65 patients with 24 month follow-up. Of these 65 patients, 70% were female, with a mean age of 70 ± 14 years and an average body mass index (BMI) of BMI of 30.5 ± 6. The mean great saphenous vein diameter in the upper thigh was 7.6 mm and the mean treatment length was 39 cm. Adjunctive treatment of the varicosities was performed in 14% of patients during the procedure. Closure rates were 100% at one week, 98% at three months, 95% at 12 months, and 92% at 24 months. There was one patient with complete and four with partial recanalization ranging from 7 to 12 cm (mean length 9 cm). There was significant improvement in CEAP and venous clinical severity score (P < .001) for all time intervals. Conclusion Early high occlusion rate with mechanochemical ablation is associated with significant clinical improvement which is maintained at 24 months, making it a very good option for the treatment of great saphenous vein incompetence.

Correction: Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn(4+)/Mn(5+) charge distribution

Correction for ‘Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba₇Li_1.75Mn_3.5O_15.75 with Mn⁴⁺/Mn⁵⁺ charge distribution’ by N. V. Tarakina et al., Dalton Trans., 2015, DOI: 10.1039/c5dt01528f.

Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn(4+)/Mn(5+) charge distribution

Ba7Li1.75Mn3.5O15.75 is a new hexagonal perovskite whose crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. It has been synthesized via a solid-state microwave route. The crystal structure was solved using a combination of X-ray and neutron diffraction data, which show that Ba7Li1.75Mn3.5O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) Å and c = 16.7467(1) Å (V = 465.063(4) Å(3)), with one formula unit, and can be described as columns of face-shared octahedra occupied by Mn(4+) and Li(+) cations and vacancies along the c axis separated in the ab plane by barium atoms. Every sixth layer, the coordination of Mn(5+) and Li(+) changes to tetrahedral. Additional local ordering of manganese and lithium atoms among cationic sites leading to the formation of a rhombohedral supercell has been observed by scanning transmission electron microscopy.

Magneto-optics of massive dirac fermions in bulk Bi2Se3

We report on magneto-optical studies of Bi2Se3, a representative member of the 3D topological insulator family. Its electronic states in bulk are shown to be well described by a simple Dirac-type Hamiltonian for massive particles with only two parameters: the fundamental band gap and the band velocity. In a magnetic field, this model implies a unique property-spin splitting equal to twice the cyclotron energy: Es=2Ec. This explains the extensive magnetotransport studies concluding a fortuitous degeneracy of the spin and orbital split Landau levels in this material. The Es=2Ec match differentiates the massive Dirac electrons in bulk Bi2Se3 from those in quantum electrodynamics, for which Es=Ec always holds.

Nonsinusoidal current-phase relationship in Josephson junctions from the 3D topological insulator HgTe

We use superconducting quantum interference device microscopy to characterize the current-phase relation (CPR) of Josephson junctions from the three-dimensional topological insulator HgTe (3D HgTe). We find clear skewness in the CPRs of HgTe junctions ranging in length from 200 to 600 nm. The skewness indicates that the Josephson current is predominantly carried by Andreev bound states with high transmittance, and the fact that the skewness persists in junctions that are longer than the mean free path suggests that the effect may be related to the helical nature of the Andreev bound states in the surface of HgTe. These experimental results suggest that the topological properties of the normal state can be inherited by the induced superconducting state, and that 3D HgTe is a promising material for realizing the many exciting proposals that require a topological superconductor.

Suppressing twin formation in Bi2Se3thin films

The goal of the present work was to reveal the origin of the formation of different structural defects in Bi2Se3 thin films. We conducted a detailed comparative study of layers grown on InP(111)A and -B terminated flat and rough substrates using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray reflectivity (XRR), X-ray diffraction (XRD) and probe-corrected scanning transmission electron microscopy (STEM). This choice of substrate reduces the formation of mosaicity twist sufficiently due to an almost perfect lattice match (0.2%) between InP and Bi2Se3. The use of substrates with different terminations and roughnesses allows the factors that define twin formation to be identified, providing conclusions about how twinning can be controlled and suppressed. In particular we have shown that growth using molecular beam epitaxy on rough Fe-doped InP(111) substrates leads to the formation of high quality thin films, with very low mosaicity twist and with complete suppression of twins in the Bi2Se3 thin films. No extra layer was observed at the interface between the film and the substrate. We also showed that the substrate surface termination (A or B) defines which family of twin domains dominates. The only types of structural defects that remain in the films are antiphase grain boundaries associated with the variation in substrate height. We believe that our study is relevant not only for Bi2Se3 growth but that it also provides essential insight for obtaining monocrystalline A2B3 (A = Bi, Sb; B = Se, Te) chalcogenide thin films and for realizing desirable electrical properties within this class of materials.

Spin texture of Bi2Se3 thin films in the quantum tunneling limit

By means of spin- and angle-resolved photoelectron spectroscopy we studied the spin structure of thin films of the topological insulator Bi2Se3 grown on InP(111). For thicknesses below six quintuple layers the spin-polarized metallic topological surface states interact with each other via quantum tunneling and a gap opens. Our measurements show that the resulting surface states can be described by massive Dirac cones which are split in a Rashba-like manner due to the substrate induced inversion asymmetry. The inner and the outer Rashba branches have distinct localization in the top and the bottom part of the film, whereas the band apices are delocalized throughout the entire film. Supported by calculations, our observations help in the understanding of the evolution of the surface states at the topological phase transition and provide the groundwork for the realization of two-dimensional spintronic devices based on topological semiconductors.

Induced superconductivity in the three-dimensional topological insulator HgTe

A strained and undoped HgTe layer is a three-dimensional topological insulator, in which electronic transport occurs dominantly through its surface states. In this Letter, we present transport measurements on HgTe-based Josephson junctions with Nb as a superconductor. Although the Nb-HgTe interfaces have a low transparency, we observe a strong zero-bias anomaly in the differential resistance measurements. This anomaly originates from proximity-induced superconductivity in the HgTe surface states. In the most transparent junction, we observe periodic oscillations of the differential resistance as a function of an applied magnetic field, which correspond to a Fraunhofer-like pattern. This unambiguously shows that a precursor of the Josephson effect occurs in the topological surface states of HgTe.

Fabrication of magnetic artificial atoms

We have fabricated gated vertical quantum dots made from a II-VI semiconductor heterostructure containing a paramagnetic quantum well. The absence of a known Schottky gate metal compatible with ZnSe based material precludes the traditional method of using a self-aligning shadow evaporated gate. Instead, we make use of a multi-step electron beam lithography process to surround a pillar with an insulating dielectric and gate. This process allows for the processing of dots with diameters down to 250 nm. Preliminary transport data confirming the magnetic nature of the resulting artificial atom are presented.

Diffusion thermopower of (Ga,Mn)As/GaAs tunnel junctions

We report the observation of tunneling anisotropic magnetothermopower, a voltage response to a temperature difference across an interface between a normal and a magnetic semiconductor. The resulting voltage is related to the energy derivative of the density of states in the magnetic material, and thus has a strongly anisotropic response to the direction of magnetization in the material. The effect will have relevance to the operation of semiconductor spintronic devices, and may indeed already play a role in correctly interpreting the details of some earlier spin injection studies.

Fully electrical read-write device out of a ferromagnetic semiconductor

We report the realization of a read-write device out of the ferromagnetic semiconductor (Ga,Mn)As as the first step to a fundamentally new information processing paradigm. Writing the magnetic state is achieved by current-induced switching and readout of the state is done by the means of the tunneling anisotropic magnetoresistance effect. This 1 bit demonstrator device can be used to design an electrically programmable memory and logic device.

Photoinduced Barkhausen effect in the ferromagnetic semiconductor (Ga,Mn)As

Magnetization of ferromagnetic materials commonly occurs via random jumps of domain walls between pinning sites, a phenomenon known as the Barkhausen effect. Using strongly focused light pulses of appropriate power and duration we demonstrate the ability to selectively activate single jumps in the domain wall propagation in (Ga,Mn)As, manifesting itself as a discrete photoinduced domain wall creep as a function of illumination time. The propagation velocity can be increased over 7 orders of magnitude varying the illumination power density and the magnetic field.

Independent magnetization behavior of a ferromagnetic metal-semiconductor hybrid system

We report the discovery of an effect where two ferromagnetic materials, one semiconductor [(Ga,Mn)As] and one metal (Permalloy), can be directly deposited on each other and still switch their magnetization independently. We use this independent magnetization behavior to create various resistance states dependent on the magnetization direction of the individual layers. At zero magnetic field a two layer device can reach up to four nonvolatile resistance states.

Nonthermal photocoercivity effect in a low-doped (Ga,Mn)As ferromagnetic semiconductor

We report a photoinduced change of the coercive field, i.e., a photocoercivity effect (PCE), under very low intensity illumination of a low-doped (Ga,Mn)As ferromagnetic semiconductor. We find a strong correlation between the PCE and the sample resistivity. Spatially resolved dynamics of the magnetization reversal rule out any role of thermal heating in the origin of this PCE, and we propose a mechanism based on the light-induced lowering of the domain wall pinning energy. The PCE is local and reversible, allowing writing and erasing of magnetic images using light.

Control of magnetic anisotropy in (Ga,Mn)as by lithography-induced strain relaxation

We report control of magnetic anisotropy in epitaxial (Ga,Mn)As by anisotropic strain relaxation in patterned structures. The strain in the structures is characterized using reciprocal space mapping by x-ray techniques. The magnetic anisotropy before patterning of the layer, which shows biaxial easy axes along [100] and [010], is replaced by a hard axis in the direction of large elastic strain relaxation and a uniaxial easy axis in the direction where pseudomorphic conditions are retained.

Magnetization-switched metal-insulator transition in a (Ga,Mn)as tunnel device

We observe the occurrence of an Efros-Shklovskii gap in (Ga,Mn)As based tunnel junctions. The occurrence of the gap is controlled by the extent of the hole wave function on the Mn acceptor atoms. Using k.p-type calculations we show that this extent depends crucially on the direction of the magnetization in the (Ga,Mn)As (which has two almost equivalent easy axes). This implies one can reversibly tune the system into the insulating or metallic state by changing the magnetization.

Remanent zero field spin splitting of self-assembled quantum dots in a paramagnetic host

We report on the observation of a finite spin splitting at zero magnetic field in resonant tunneling experiments on CdSe self-assembled quantum dots in a (Zn,Be,Mn)Se barrier. This is remarkable since bulk II-VI dilute magnetic semiconductors are paramagnets. Our experiment may be viewed as tunneling through a single magnetic polaron, where the carriers contained inside the dot act to mediate an effective ferromagnetic interaction between Mn ions in their vicinity. The effect is observable up to relatively high temperatures, which we tentatively ascribe to a feedback mechanism with the electrical current, previously predicted theoretically.

General practice critical incident reviews of patient suicides: benefits, barriers, costs, and family participation

AIM

To explore the feasibility of holding critical incident reviews (CIRs) after patient suicides in general practice and their ability to change practice.

METHODS

Thirteen practices were invited to conduct a facilitated CIR on 18 current patient suicides. Next of kin views were sought. All staff attending a CIR were interviewed after the review.

RESULTS

Ten practices reviewed 12 deaths. Twenty six staff attended reviews; all were interviewed. Next of kin contributed to six reviews; only one criticised care. Changes following the reviews included steps to improve internal communication and bereavement support to set up internal CIRs and review prescribing policies. Communications between practices and other agencies were clarified.

CONCLUSION

Practices were willing to hold CIRs and appreciated the potential positive value but need reassurance that they will not be blamed for suicides, and that the cost in time and resources will be recognised.

Very large tunneling anisotropic magnetoresistance of a (Ga,Mn)As/GaAs/(Ga,Mn)As stack

We report the discovery of a very large tunneling anisotropic magnetoresistance in an epitaxially grown (Ga,Mn)As/GaAs/(Ga,Mn)As structure. The key novel spintronics features of this effect are as follows: (i) both normal and inverted spin-valve-like signals; (ii) a large nonhysteretic magnetoresistance for magnetic fields perpendicular to the interfaces; (iii) magnetization orientations for extremal resistance are, in general, not aligned with the magnetic easy and hard axis; (iv) enormous amplification of the effect at low bias and temperatures.

Tunneling anisotropic magnetoresistance: a spin-valve-like tunnel magnetoresistance using a single magnetic layer

We introduce a new class of spintronic devices in which a spin-valve-like effect results from strong spin-orbit coupling in a single ferromagnetic layer rather than from injection and detection of a spin-polarized current by two coupled ferromagnets. The effect is observed in a normal-metal-insulator-ferromagnetic-semiconductor tunneling device. This behavior is caused by the interplay of the anisotropic density of states in (Ga,Mn)As with respect to the magnetization direction and the two-step magnetization reversal process in this material.

Spin injection in the nonlinear regime: band bending effects

We report on electrical spin-injection measurements into a nonmagnetic semiconductor in the nonlinear regime. For voltage drops across the interface larger than a few mV the spin-injection efficiency decreases strongly. The effect is caused by repopulation of the minority spin level in the magnetic semiconductor due to band bending at the interface.

Very large magnetoresistance in lateral ferromagnetic (Ga,Mn)as wires with nanoconstrictions

We have fabricated (Ga,Mn)As nanostructures in which domain walls can be pinned by sub-10 nm constrictions. Controlled by shape anisotropy, we can switch the regions on either side of the constriction to either parallel or antiparallel magnetization. All samples exhibit a positive magnetoresistance, consistent with domain-wall trapping. For metallic samples, we find a magnetoresistance up to 8%, which can be understood from spin accumulation. In samples where, due to depletion at the constriction, a tunnel barrier is formed, we observe a magnetoresistance of up to 2000%.

Voltage-controlled spin selection in a magnetic resonant tunneling diode

We have fabricated all II-VI semiconductor resonant tunneling diodes based on the (Zn,Mn,Be)Se material system, containing dilute magnetic material in the quantum well, and studied their current-voltage characteristics. When subjected to an external magnetic field the resulting spin splitting of the levels in the quantum well leads to a splitting of the transmission resonance into two separate peaks. This is interpreted as evidence of tunneling transport through spin polarized levels, and could be the first step towards a voltage controlled spin filter.

Large magnetoresistance effect due to spin injection into a nonmagnetic semiconductor

A novel magnetoresistance effect, due to the injection of a spin-polarized electron current from a dilute magnetic into a nonmagnetic semiconductor, is presented. The effect results from the suppression of a spin channel in the nonmagnetic semiconductor and can theoretically yield a positive magnetoresistance of 100%, when the spin flip length in the nonmagnetic semiconductor is sufficiently large. Experimentally, our devices exhibit up to 25% magnetoresistance.

Observational study of effect of patient centredness and positive approach on outcomes of general practice consultations

OBJECTIVE

To measure patients' perceptions of patient centredness and the relation of these perceptions to outcomes.

DESIGN

Observational study using questionnaires.

SETTING

Three general practices.

PARTICIPANTS

865 consecutive patients attending the practices.

MAIN OUTCOME MEASURES

Patients' enablement, satisfaction, and burden of symptoms.

RESULTS

Factor analysis identified five components. These were communication and partnership (a sympathetic doctor interested in patients' worries and expectations and who discusses and agrees the problem and treatment, Cronbach's alpha=0.96); personal relationship (a doctor who knows the patient and their emotional needs, alpha=0.89); health promotion (alpha=0.87); positive approach (being definite about the problem and when it would settle, alpha=0.84); and interest in effect on patient's life (alpha=0.89). Satisfaction was related to communication and partnership (adjusted beta=19.1; 95% confidence interval 17.7 to 20.7) and a positive approach (4.28; 2.96 to 5.60). Enablement was greater with interest in the effect on life (0.55; 0.25 to 0.86), health promotion (0.57; 0.30 to 0.85), and a positive approach (0.82; 0.52 to 1.11). A positive approach was also associated with reduced symptom burden at one month (beta=-0.25; -0.41 to -0.10). Referrals were fewer if patients felt they had a personal relationship with their doctor (odds ratio 0.70; 0.54 to 0.90).

CONCLUSIONS

Components of patients' perceptions can be measured reliably and predict different outcomes. If doctors don't provide a positive, patient centred approach patients will be less satisfied, less enabled, and may have greater symptom burden and higher rates of referral.

Preferences of patients for patient centred approach to consultation in primary care: observational study

OBJECTIVE

To identify patient's preferences for patient centred consultation in general practice.

DESIGN

Questionnaire study.

SETTING

Consecutive patients in the waiting room of three doctors' surgeries.

MAIN OUTCOME MEASURES

Key domains of patient centredness from the patient perspective. Predictors of preferences for patient centredness, a prescription, and examination.

RESULTS

865 patients participated: 824 (95%) returned the pre-consultation questionnaire and were similar in demographic characteristic to national samples. Factor analysis identified three domains of patient preferences: communication (agreed with by 88-99%), partnership (77-87%), and health promotion (85-89%). Fewer wanted an examination (63%), and only a quarter wanted a prescription. As desire for a prescription was modestly associated with desire for good communication (odds ratio 1.20; 95% confidence interval 0.85 to 1.69), partnership (1.46; 1.01 to 2.09), and health promotion (1.61; 1.12 to 2.31) this study may have underestimated preferences for patient centredness compared with populations with stronger preferences for a prescription. Patients who strongly wanted good communication were more likely to feel unwell (very, moderately, and slightly unwell; odds ratios 1, 0.56, 0.39 respectively, z trend P<0.001), be high attenders (1.70; 1.18 to 2.44), and have no paid work (1.84; 1.21 to 2.79). Strongly wanting partnership was also related to feeling unwell, worrying about the problem, high attendance, and no paid work; and health promotion to high attendance and worry.

CONCLUSION

Patients in primary care strongly want a patient centred approach, with communication, partnership, and health promotion. Doctors should be sensitive to patients who have a strong preference for patient centredness-those vulnerable either psychosocially or because they are feeling unwell.

Pragmatic randomised controlled trial of two prescribing strategies for childhood acute otitis media

OBJECTIVE

To compare immediate with delayed prescribing of antibiotics for acute otitis media.

DESIGN

Open randomised controlled trial.

SETTING

General practices in south west England.

PARTICIPANTS

315 children aged between 6 months and 10 years presenting with acute otitis media.

INTERVENTIONS

Two treatment strategies, supported by standardised advice sheets-immediate antibiotics or delayed antibiotics (antibiotic prescription to be collected at parents' discretion after 72 hours if child still not improving).

MAIN OUTCOME MEASURES

Symptom resolution, absence from school or nursery, paracetamol consumption.

RESULTS

On average, symptoms resolved after 3 days. Children prescribed antibiotics immediately had shorter illness (-1.1 days (95% confidence interval -0.54 to -1.48)), fewer nights disturbed (-0.72 (-0.30 to -1.13)), and slightly less paracetamol consumption (-0.52 spoons/day (-0.26 to -0.79)). There was no difference in school absence or pain or distress scores since benefits of antibiotics occurred mainly after the first 24 hours-when distress was less severe. Parents of 36/150 of the children given delayed prescriptions used antibiotics, and 77% were very satisfied. Fewer children in the delayed group had diarrhoea (14/150 (9%) v 25/135 (19%), chi(2)=5.2, P=0.02). Fewer parents in the delayed group believed in the effectiveness of antibiotics and in the need to see the doctor with future episodes.

CONCLUSION

Immediate antibiotic prescription provided symptomatic benefit mainly after first 24 hours, when symptoms were already resolving. For children who are not very unwell systemically, a wait and see approach seems feasible and acceptable to parents and should substantially reduce the use of antibiotics for acute otitis media.

UK neonatal intensive care services in 1996. On behalf of the UK Neonatal Staffing Study Collaborative Group

A census of activity and staff levels in 1996 was conducted in UK neonatal units and achieved a 100% response from 246 units. Among the 186 neonatal intensive care units, the median (interquartile range) number of total cots was 18(14-22); level 1 intensive care cots 4(2-6); total admissions 318(262-405); very low birthweight admissions 40(28-68); and the number ventilated or given CPAP by endotracheal tube 52(32-83). Forty six (25%) intensive care units lacked the recommended minimum of one consultant with prime responsibility for neonatal medicine. As a conservative estimate 79% of intensive care units had a lower nursing provision than that recommended in previously published guidelines. There was substantial variation in activity and staffing levels among units.

Risk-factor assessment for falls: from a written checklist to the penless clinic

OBJECTIVE

to audit risk-factor identification of fallers before and after an education programme and the insertion of a written checklist in medical notes. Risk-factor identification in a dedicated, computerized falls clinic was then examined.

METHODS

documentation of risk factors for falls was studied on wards and a self-auditing 'penless' clinic for fallers subsequently set up to generate reports for medical notes and letters for general practitioners.

RESULTS

risk-factor identification improved after the insertion of the checklist but remained relatively poor. A dedicated clinic allowed almost complete identification of risk factors. Of the first 112 patients (median age 82) seen in the clinic, 75 (67%) were housebound. Remediable risk factors--e.g. inappropriate medication (67%), unsatisfactory footwear (59%) and postural hypotension (17%)--were found in most. Thirty-three patients (29%) had difficulty with alarm raising.

CONCLUSION

ward-based intervention showed limited capacity to identify risk factors for falls: a dedicated clinic was more successful. The use of a portable computer with a programme to screen fallers for risk factors is worthy of consideration.

Reattendance and complications in a randomised trial of prescribing strategies for sore throat: the medicalising effect of prescribing antibiotics

OBJECTIVE

To assess the medicalising effect of prescribing antibiotics for sore throat.

SETTING

11 general practices in England.

DESIGN

Randomised trial of three approaches to sore throat: a 10 day prescription of antibiotics, no antibiotics, or a delayed prescription if the sore throat had not started to settle after three days.

PATIENTS

716 patients aged 4 and over with sore throat and an abnormal physical sign: 84% had tonsillitis or pharyngitis.

OUTCOME MEASURES

Number and rate of patients making a first return with sore throat, pharyngitis, or tonsillitis. Early returns (within two weeks) and complications (otitis media, sinusitis, quinsy). Outcomes were documented in 675 subjects (94%).

RESULTS

Mean follow up time was similar (antibiotic group 1.07 years, other two groups 1.03 years). More of those initially prescribed antibiotics initially returned to the surgery with sore throat (38% v 27%, adjusted hazard ratio for return 1.39%, 95% confidence interval 1.03 to 1.89). Antibiotics prescribed for sore throat during the previous year had an additional effect (hazard ratio 1.69, 1.20 to 2.37). Longer duration of illness (> 5 days) was associated with increased return within six weeks (hazard ratio 2.90, 1.70 to 4.92). Prior attendance with upper respiratory conditions was also associated with increased reattendance. There was no difference between groups in early return (13/238 (5.5%) v 27/437 (6%)), or complications (2/236 (0.8%) v 3/434 (0.7%)).

CONCLUSIONS

Complications and early return resulting from no or delayed prescribing of antibiotics for sore throat are rare. Both current and previous prescribing for sore throat increase reattendance. To avoid medicalising a self limiting illness doctors should avoid antibiotics or offer a delayed prescription for most patients with sore throat.

Detection of an atypical 22q11 deletion that has no overlap with the DiGeorge syndrome critical region

Images

Open randomised trial of prescribing strategies in managing sore throat

OBJECTIVE

To assess three prescribing strategies for sore throat.

DESIGN

Randomised follow up study.

SETTING

11 general practices in the South and West region.

SUBJECTS

716 patients aged 4 years and over with sore throat and an abnormal physical sign in the throat; 84% had tonsillitis or pharyngitis. Patients were randomised to three groups: prescription for antibiotics for 10 days (group 1,246 patients); no prescription (group 2,230 patients); or prescription for antibiotics if symptoms were not starting to settle after three days (group 3; 238 patients).

MAIN OUTCOME MEASURES

Duration of symptoms; satisfaction and compliance with and perceived efficacy of antibiotics; time off school or work. Outcomes were documented in 582 subjects (81%).

RESULTS

Median duration of antibiotic use differed significantly in the three groups (10 v 0 v 0 days, P < 0.001); 69% of patients in group 3 did not use their prescription. The proportion of patients better by day 3 did not differ significantly (37% v 35% v 30%, P = 0.28), nor did the duration of illness (median 4 v 5 v 5 days, P = 0.39), days off work or school (median 2 v 2 v 1, P = 0.13), or proportion of patients satisfied (96% v 90% v 93%, P = 0.09), although group 1 had fewer days of fever (median 1 v 2 v 2 days, P = 0.04). More patients in group 1 thought the antibiotics were effective (87% v 55% v 60%, P < 0.001) and intended coming to the doctor in future attacks (79% v 54% v 57%, P < 0.001). "Legitimation" of illness-to explain to work or school (60%) or family or friends (37%)-was an important reason for consultation. Patients who were more satisfied got better more quickly, and satisfaction related strongly to how well the doctor dealt with patient's concerns.

CONCLUSION

Prescribing antibiotics for sore throat only marginally affects the resolution of symptoms but enhances belief in antibiotics and intention to consult in future when compared with the acceptable strategies of no prescription or delayed prescription. Psychosocial factors are important in the decision to see a general practitioner and in predicting the duration of illness.