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Avalanche Photodiodes (APDs) are key semiconductor components that amplify weak optical signals via the impact ionization process, but this process’ stochastic nature introduces ‘excess’ noise, limiting the useful signal to noise ratio (or sensitivity) that is practically achievable. The APD material’s electron and hole ionization coefficients (α and β respectively) are critical parameters in this regard, with very disparate values of α and β necessary to minimize this excess noise. Here, the analysis of thirteen complementary p-i-n/n-i-p diodes shows that alloying GaAs with ≤ 5.1 % Bi dramatically reduces β while leaving α virtually unchanged—enabling a 2 to 100-fold enhancement of the GaAs α/β ratio while extending the wavelength beyond 1.1 µm. Such a dramatic change in only β is unseen in any other dilute alloy and is attributed to the Bi-induced increase of the spin-orbit splitting energy (∆so). Valence band engineering in this way offers an attractive route to enable low noise semiconductor APDs to be developed., An avalanche photodiode is an opto-electronic amplifier that uses impact ionization to provide enhanced sensitivity at the expense of excess noise. In this manuscript, the authors demonstrate that a small amount of Bismuth (Bi) in Gallium Arsenide (GaAs) avalanche photodiodes significantly reduces this excess noise.

The α-Gal mammalian meat allergy classically presents with urticaria, with or without gastrointestinal (GI) symptoms or anaphylaxis, but increasingly we are aware of patients with only GI symptoms. Here we describe patients presenting with isolated GI symptoms who had detectable IgE antibodies to α-Gal and reported symptom improvement on a mammal-restricted diet. Forty patients in the practice of a single gastroenterologist, and 35 patients in one allergy clinic were identified, with abdominal pain, diarrhea, and nausea the most common symptoms. Alpha-Gal IgE levels were lower than in a previously described cohort of patients who exhibited classic allergic reactions. This large case series suggests that α-Gal IgE is an important contributor to GI morbidity in areas where lone star tick bites are common. Symptom presentations in GI-AGS can be easily confused with other common GI conditions, and α-Gal IgE levels are often lower than those in patients with classic AGS.

Objectives Immunoglobulin E (IgE) to galactose-α-1,3-galactose (alpha-gal) is a recently appreciated cause of allergic reactions to mammalian meat and dairy. In eastern North America Lone Star tick bites are the dominant mode of sensitization. Classically the alpha-gal syndrome manifests with urticaria, gastrointestinal symptoms, and/or anaphylaxis, but increasingly there are reports of isolated gastrointestinal symptoms without other common allergic manifestations. The objective of this retrospective study was to determine the frequency of IgE to alpha-gal in patients presenting with unexplained gastrointestinal symptoms to a community gastroenterology practice, and to evaluate the symptom response to the removal of mammalian products from the diet in alpha-gal-positive individuals. Methods An electronic medical record database was used to identify patients with alpha-gal IgE laboratory testing performed within the past 4 years. These charts were reviewed for alpha-gal test results, abdominal pain, diarrhea, nausea and vomiting, hives, bronchospasm, diagnosis of irritable bowel syndrome, postprandial exacerbation of symptoms, meat exacerbation of symptoms, patient recall of tick bite, other simultaneous gastrointestinal tract diagnoses, and clinical improvement with mammalian food product avoidance. Results A total of 1112 adult patients underwent alpha-gal IgE testing and 359 (32.3%) were positive. Gastrointestinal symptoms were similar in those positive and negative for alpha-gal seroreactivity. Of the 359 alpha-gal-positive patients, 122 had follow-up data available and 82.0% of these improved on a diet free of mammalian products. Few patients reported hives (3.9%) or bronchospasm (2.2%). Serum alpha-gal IgE titers ranged from 0.1 to >100 kU/L, with an average of 3.43 kU/L and a median of 0.94 kU/L. Conclusions Clinicians practicing in the region of the Lone Star tick habitat need to be aware that patients with IgE to alpha-gal can manifest with isolated abdominal pain and diarrhea, and these patients respond well to dietary exclusion of mammalian products.

GaAs/GaNAsBi/GaAs core–multishell nanowires were grown using molecular beam epitaxy on Si(111) substrates. The formation of the 20 nm-wide GaNAsBi shell with a regular hexagonal structure was observed. The shell is estimated to contain approximately 1.5% N and 2.6% Bi and has a compressive lattice mismatch of less than 0.2 % with GaAs layers. The strain mediation by the introduction of both N and Bi suppresses the crystalline deformation, resulting in the clear formation of the GaNAsBi shell. Thus, we obtained room-temperature photoluminescence with the maximum position at approximately 1300 nm from the GaAs/GaNAsBi/GaAs core–multishell nanowires.

Join John Lincoln, Natalie Wheeler, Richard Carter, Rob Richards, and Kasia Balakier as they present a vision for the future of photonics, identifying the key topics that will be the focus of research a decade or more from now. Based on the collective input of 26 of the UK’s leading photonics academics, 70 key topics are highlighted for future research focus across materials, optical and physical phenomena, future manufacturing processes, device and systems. This unique horizon scanning exercise, jointly published with the All Party Parliamentary Group on Photonics and Quantum, aims to stimulate engagement from government, funding agencies and industry to shape future innovation strategy and to inspire the next generation of researchers.

InAsBi dilute alloys are potential new candidates for the improvement of infrared optoelectronic devices such as photodetectors or lasers. In this work, InAsBi/InAs superlattices (SLs) with Bi contents ranging between 1 and 3% were grown by molecular beam epitaxy with different Bi fluxes and growth temperatures to analyze Bi segregation by cross sectional transmission electron microscopy techniques. Bi segregation profiles have been described layer-by-layer using a three-layer fluid exchange mechanism, extracting the values of the As/Bi exchange energies (E1, 1.26 ± 0.01 eV and E2, 1.36 ± 0.02 eV). A relationship to calculate the activation energies for exchange from the binding energies in III–V alloys is proposed, which would allow predicting them for other hitherto unknown compounds.

The dark current characteristics of two series of bulk GaAsBi p-i-n diodes are analysed as functions of temperature and band gap. Each temperature dependent measurement indicates that recombination current dominates in these devices. The band gap dependence of the dark currents is also consistent with recombination dominated current for the devices grown at a common growth temperature, indicating that the presence of Bi does not directly adversely affect the dark currents. However, the devices grown at different growth temperatures exhibit a faster increase in dark current with decreasing device band gap, suggesting that a reduced growth temperature causes a reduction in minority carrier lifetime.

GaAsBi light emitting diodes containing ∼6% Bi are grown on GaAs substrates. Good room-temperature electroluminescence spectra are obtained at current densities as low as 8 Acm − 2. Measurements of the integrated emitted luminescence suggest that there is a continuum of localised Bi states extending up to 75 meV into the bandgap, which is in good agreement with previous photoluminescence studies. X-ray diffraction analysis shows that strain relaxation has probably occurred in the thicker samples grown in this study.

Dilute bismide III-V semiconductors have many unique properties and have been extensively investigated in recent decades. As the development of material research has progressed, some promising dilute bismide devices have been explored. Incorporation of a small amount of Bi in III-V host materials results in a large band-gap narrowing, which makes dilute bismides potential candidates in long-wavelength photodetectors. In this chapter, we review recent progress on GaAsBi, InAsBi, InSbBi, and InGaAsBi photodetectors, as well as GaAsBi and InGaAsBi THz photoconductive detectors. Some preliminary demonstrations and detector properties have been reported on these dilute bismide photodetectors, while the material quality still needs to be improved and the specific detector properties of dilute bismides still need more understanding.

The Bi content in GaAs/GaAs1 − xBi x /GaAs heterostructures grown by molecular beam epitaxy at a substrate temperature close to 340 °C is investigated by aberration-corrected high-angle annular dark-field techniques. The analysis at low magnification of high-angle annular dark-field scanning transmission electron microscopy images, corroborated by EDX analysis, revealed planar defect-free layers and a non-homogeneous Bi distribution at the interfaces and within the GaAsBi layer. At high magnification, the qHAADF analysis confirmed the inhomogeneous distribution and Bi segregation at the GaAsBi/GaAs interface at low Bi flux and distorted dumbbell shape in areas with higher Bi content. At higher Bi flux, the size of the Bi gathering increases leading to roughly equiaxial Bi-rich particles faceted along zinc blende {111} and uniformly dispersed around the matrix and interfaces. FFT analysis checks the coexistence of two phases in some clusters: a rhombohedral pure Bi (rh-Bi) one surrounded by a zinc blende GaAs1 − xBi x matrix. Clusters may be affecting to the local lattice relaxation and leading to a partially relaxed GaAsBi/GaAs system, in good agreement with XRD analysis.

A comprehensive assessment of the nature of the distribution of sub band-gap energy states in bulk GaAsBi is presented using power and temperature dependent photoluminescence spectroscopy. The observation of a characteristic red-blue-red shift in the peak luminescence energy indicates the presence of short-range alloy disorder in the material. A decrease in the carrier localisation energy demonstrates the strong excitation power dependence of localised state behaviour and is attributed to the filling of energy states furthest from the valence band edge. Analysis of the photoluminescence lineshape at low temperature presents strong evidence for a Gaussian distribution of localised states that extends from the valence band edge. Furthermore, a rate model is employed to understand the non-uniform thermal quenching of the photoluminescence and indicates the presence of two Gaussian-like distributions making up the density of localised states. These components are attributed to the presence of microscopic fluctuations in Bi content, due to short-range alloy disorder across the GaAsBi layer, and the formation of Bi related point defects, resulting from low temperature growth.

A series of GaAsBi/GaAs multiple quantum well p–i–n diodes were grown by molecular beam epitaxy. Nomarski images showed evidence of sub-surface damage in each diode, with an increase in the cross-hatching associated with strain relaxation for the diodes containing more than 40 quantum wells. X-ray diffraction ω–2θ scans of the (004) reflections showed that multiple quantum well regions with clearly defined well periodicities were grown. The superlattice peaks of the diodes containing more than 40 wells were much broader than those of the other diodes. The photoluminescence spectra showed a redshift of 56meV and an attenuation of nearly two orders of magnitude for the 54 and 63 well diodes. Calculations of the quantum confinement and strain induced band gap modifications suggest that the wells in all diodes are thinner than their intended widths and that both loss of quantum confinement and strain probably contributed to the observed redshift and attenuation in the 54 and 63 well diodes. Comparison of this data with that gathered for InGaAs/GaAs multiple quantum wells, suggests that the onset of relaxation occurs at a similar average strain–thickness product for both systems. Given the rapid band gap reduction of GaAsBi with Bi incorporation, this data suggests that GaAsBi is a promising photovoltaic material candidate.

Deep-level defects in n-type GaAs1−x Bi x having 0 ≤ x ≤ 0.023 grown on GaAs by molecular beam epitaxy at substrate temperature of 378 °C have been injvestigated by deep level transient spectroscopy. The optical properties of the layers have been studied by contactless electroreflectance and photoluminescence. We find that incorporating Bi suppresses the formation of GaAs-like electron traps, thus reducing the total trap concentration in dilute GaAsBi layers by over two orders of magnitude compared to GaAs grown under the same conditions. In order to distinguish between Bi- and host-related traps and to identify their possible origin, we used the GaAsBi band gap diagram to correlate their activation energies in samples with different Bi contents. This approach was recently successfully applied for the identification of electron traps in n-type GaAs1−x N x and assumes that the activation energy of electron traps decreases with the Bi (or N)-related downward shift of the conduction band. On the basis of this diagram and under the support of recent theoretical calculations, at least two Bi-related traps were revealed and associated with Bi pair defects, i.e. (VGa+BiGa)−/2− and (AsGa+BiGa)0/1−. In the present work it is shown that these defects also influence the photoluminescence properties of GaAsBi alloys.

Annular dark-field (ADF) imaging in a scanning transmission electron microscope (STEM) has been used to measure concentration profiles across thin Ga(As,Bi) layers grown by molecular beam epitaxy, from which the segregation lengths for bismuth surface segregation have been calculated. Performing this for layers grown at two different temperatures, the activation energies for Bi surface segregation have been determined for the lower (GaAsBi-on-GaAs) and for the upper (GaAs-on-GaAsBi) interface. The inequivalence observed is attributed to strain driving the larger Bi atoms preferably towards the free surface during growth.

The structural and optical properties of GaAs1−xBix alloys for x up to 0.108 have been investigated by high resolution X-ray diffraction and photoluminescence (PL). At room temperature (RT), the PL intensity of the GaAs0.97Bi0.03 sample was found to be ∼300 times higher than a GaAs control sample grown at the same temperature (400 °C). PL measurements carried out at 10 K show that when excitation power, Pex was increased from 0.11 to 1140 W cm−2, the PL peak energy blue-shifts by 80 meV while the full-width-at-half-maximum reduces from 115 to 63 meV. However, the PL peak emission energy becomes independent of the excitation power at RT. The results indicate the presence of localized energy states in the GaAs0.97Bi0.03 sample, which trap carriers at low temperatures and that the majority of the carriers become delocalized at RT. Furthermore, the temperature dependent PL also shows an S-shape behavior, which is a signature of localization effects. A theoretical model, which was derived by solving a rate equation was employed. The model successfully reproduces the observed S-shape behavior and the theory fits well with the experimental data. The RT band gap of GaAs1−xBix for x up to 0.108 has been plotted and compared with the literature.

100 nm thick GaAsBi layers were grown at a range of temperatures using both As 2 and As 4 . Measurements of Bi incorporation based on room temperature photoluminescence spectra indicate that the growth temperature dependence of Bi incorporation is the same for both As species and is invariant with respect to Bi flux; however, Bi incorporation saturates when the growth temperature is low enough for the Bi incorporation coefficient to reach unity. The As:Ga atomic flux ratios allowing significant Bi incorporation are coincident for both As species upon accounting for desorption of 50% of the incident As 4 atoms during GaAs growth. The Bi reconstruction lifetime at 415 °C was measured under overpressures of both As species and under vacuum. The lifetime is significantly longer than the monolayer growth time used in this work; however, results do show that As 2 is more aggressive at displacing Bi from a static surface than As 4 . The photoluminescence intensities of the samples grown in this work vary with Bi incorporation in accordance with current literature and appear to be independent of As species.

A series of GaAsBi/GaAs multiple quantum well p-i-n diodes are characterized using IV, photocurrent and illuminated IV measurements. The results are compared to an InGaAs/GaAsP multiple quantum well control device of a design that has demonstrated excellent performance in triple junction photovoltaics. The extended absorption of the GaAsBi/GaAs devices, compared to that of the InGaAs/GaAsP device, suggests that GaAsBi/GaAs could present a viable alternative to InGaAs/GaAsP for quad junction photovoltaics.

While recent work developing GaAsBi for opto-electronic applications has shown promise, it has also indicated that the large valence band offset of GaAsBi/GaAs may cause undesirable hole-trapping in GaAsBi quantum wells. In this work, hole-trapping is demonstrated to be the cause of the reduced depletion width of GaAsBi/GaAs multi-quantum well solar cell devices under illumination. Modelling of the quantum confinement energies in these devices shows how the carrier escape times vary as functions of temperature, providing a tool for the design for future GaAsBi based photovoltaic devices.

The quality of GaAsBi samples grown under various conditions were investigated by photoluminescence (PL) and atomic force microscopy (AFM). The samples were grown by molecular beam epitaxy at a rate of 0.36 and 0.61 μm/h. For each growth rates, three samples were grown under different Bi fluxes. For samples grown at a rate of 0.36 μm/h, the PL peak wavelength was red-shifted from 1103 to 1241 nm as the Bi flux was increased from 0.53 to 1.0 × 10−7 mBar. However, for sample grown with the highest Bi flux, the optical quality degraded showing a weak and broad PL spectrum. The AFM image shows that the sample grown with Bi flux of 0.53 × 10−7 mBar has a smooth surface with rms roughness of 0.78 nm. However, the presence of Bi droplets was observed for samples grown with higher Bi fluxes. A similar PL trend was also observed for samples grown at 0.61 μm/h. The results indicate that high Bi flux may increase the incorporation of Bi into GaAs but it is limited by the formation of Bi droplets.

An InAsBi photodiode has been grown, fabricated and characterized to evaluate its performance in the MWIR region of the spectrum. Spectral response from the diode has been obtained up to a diode temperature of 225 K. At this temperature the diode has a cut off wavelength of 3.95 μm, compared to 3.41 μm in a reference InAs diode, indicating that Bismuth has been successfully incorporated to reduce the band gap of InAs by 75 meV. Similar band gap reduction was deduced from the cut off wavelength comparison at 77 K. From the dark current data, R0A values of 590 MΩcm2 and 70 MΩcm2 at temperatures of 77 and 290 K respectively, were obtained in our InAsBi photodiode.

The structural and optical properties of GaAs 1−x Bi x samples with x = 0.048 and 0.06 were investigated by high resolution X-ray diffraction (HR-XRD) and photoluminescence (PL). The HR-XRD results show that both samples have a smooth and coherent GaAs 1−x Bi x /GaAs interface. The PL peak energy shows an S-shape behavior with temperature (10 K to room temperature) which is an evidence of carrier localizations. An Arrhenius analysis reveals that the thermal quenching activation energy is 30 and 19 meV for the GaAs 0.952 Bi 0.048 and GaAs 0.94 Bi 0.06 sample, respectively. It was found that the activation energy is not necessarily originated from alloy fluctuations but may also due to CuPt ordering-induced band gap fluctuations. The power dependent PL indicates that the localized energy states are continuously present and located up to 40–47 meV from the valence band.

A GaAsBi/GaAs multiple quantum well diode with a p-i-n structure including a 0.6μm i-region containing a 40 periods of 8nm well and 7.4nm barriers has been grown by molecular beam epitaxy. The photocurrent of the fabricated device was measured and compared to that of a strain-balanced 65 period InGaAs/GaAsP MQW p-i-n diode grown by metal-organic vapour phase epitaxy. The GaAsBi device exhibits an ideality factor of 1.8 and a photoluminescence peak at 1055nm. The photocurrent of the GaAsBi device was comparable to that of the InGaAs/GaAsP device at around 920nm but continued to produce current out to ~1100nm.

Raman spectroscopy and magneto-photoluminescence measurements under high magnetic fields were used to investigate the optical and spin properties of GaBiAs/GaAs multiple quantum wells (MQWs). An anomalous negative diamagnetic energy shift was observed at higher temperatures and higher laser intensities, which was associated to a sign inversion of hole effective mass in these structures. In addition, an enhancement of the polarization degree with decreasing of laser intensity was observed (experimental condition where the emission is dominated by localized excitons). This effect was explained by changes of spin relaxation and exciton recombination times due to exciton localization by disorder.

The reported incidence of sphincter of Oddi dysfunction following orthotopic liver transplantation has ranged from 3% to 7%. If sphincteric dysfunction is unrecognized, therapy may be inappropriate; when recognized, extensive surgery may be required. To prospectively identify patients with sphincteric dysfunction, we performed sphincter of Oddi motility studies through the t-tube tract three months after transplantation. Baseline sphincter motility and response to intravenous cholecystokinin were evaluated. The results of 10 subjects are reported; nine had normal basal sphincter pressure (16 +/- 5.8 mm Hg), and all had normal frequency (3.6 +/- 1/min), amplitude (86 +/- 31 mm Hg), and duration (4.5 +/- 1 sec) of phasic contractions. One subject had an elevated basal pressure (47 mm Hg). All, including the subject with elevated basal pressure, demonstrated a normal response to intravenous cholecystokinin with significant inhibition of phasic contraction frequency and amplitude. We demonstrate that simultaneous studies of the sphincter and duodenum can be obtained via the t-tube tract, providing the opportunity for prospective evaluation of sphincteric function. We conclude that sphincter of Oddi function usually remains normal following liver transplantation with choledochocholedochostomy.

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GaAsBi/GaAs multiple quantum well (MQW) p–i–n diodes are grown by molecular beam epitaxy. Transmission electron microscope images of the diodes show good agreement between the intended and measured MQW periods, but poor agreement between the intended and measured GaAsBi quantum well thicknesses. This is likely due to the incorporation of Bi from a physisorbed surface layer that takes a finite time to accumulate during growth. The diodes with more than 40 wells show dislocations that indicate strain relaxation. This is supported by x-ray diffraction analysis, which also suggests that the i-region of the 54 well diode is tilted with respect to the substrate.

The optical and structural properties of GaAsBi bulk and quantum well (QW) samples grown under various conditions were studied by photoluminescence (PL), high resolution x-ray diffraction (HR-XRD) and transmission electron microscopy (TEM). At 10 K, the 90 nm bulk sample shows two PL peaks at 1.18 and 1.3 eV. The temperature and power dependent PL data suggest that both PL peaks originate from the GaAsBi layer which consists of two regions with different Bi concentrations. The TEM images verify that the Bi concentration decreases monotonically across the layer, showing a high Bi concentration (~0.053) close to the bottom interface which then reduces to ~0.02 for thicknesses >25 nm. Besides, the high Bi content region cannot be detected by HR-XRD due to a broad and weak diffraction intensity. For multiple QW samples, a similar Bi profile was also observed in which the first well has a significantly higher Bi content compared to the other wells. The energy separation between the PL peaks is 0.12 eV and is consistent with the energy difference observed for the bulk sample. However, two PL peaks were not observed in the other GaAsBi bulk sample which was grown under different conditions, showing the importance of growth optimizations.

Photoreflectance (PR), photoluminescence (PL) and time-resolved PL were applied to study the optical properties, particularly the localized and delocalized states and carrier dynamics, in GaAs1−xBix/GaAs quantum wells. With increasing Bi concentration the ground state transition (i.e., the transition between the first heavy hole and the first electron subband) red shifts due to Bi-related reduction of the GaAs1−xBix energy gap. Additionally, the transition related to the excited states in the quantum wells is clearly observed for the sample with high Bi concentration of 5.6%, confirming these quantum wells are type I. The PL measurements show the S-shape behavior and indicate the strong localization effect below 150 K for all measured samples, while the PL emission above 150 K is related to delocalized states. The localized character of emission at low temperatures is confirmed by time-resolved PL studies. At 10 K the decay time has strong spectral dispersion (i.e. the decay time increases from ~10 ns to ~400 ns going from the high to low energy side of the PL peak). This dispersion disappears above 190 K. At room temperature the decay time is in the order of a few ns.

The absorption properties of GaAsBi have been investigated using GaAsBi based p–i–n diodes with different bismuth compositions (~2.1 and ~3.4%). The absorption behaviour of GaAsBi as a function of incident photon energy above the band gap follows that of a direct band gap material. With increasing bismuth content, the absorption of photons with energy lower than the band gap in GaAsBi is enhanced, probably due to localized states caused by Bi-related defects. A simplified analysis has been undertaken on the behaviour of absorption as a function of bias voltage. By undertaking photoresponsivity measurements as a function of reverse bias, the background doping type and the minority carriers diffusion lengths in GaAsBi have been determined.

Band gap alignment in GaAs1−xBix/GaAs quantum wells (QWs) was studied experimentally by photoreflectance (PR) and theoretically, ab initio, within the density functional theory in which the supercell based calculations are combined with the alchemical mixing approximation applied to a single atom in a supercell. In PR spectra, the optical transitions related to the excited states in the QW (i.e., the transition between the second heavy-hole and the second electron subband) were clearly observed in addition to the ground state QW transition and the GaAs barrier transition. This observation is clear experimental evidence that this is a type I QW with a deep quantum confinement in the conduction and valence bands. From the comparison of PR data with calculations of optical transitions in GaAs1−xBix/GaAs QW performed for various band gap alignments, the best agreement between experimental data and theoretical calculations has been found for the valence band offset of 52 ± 5%. A very similar valence band offse...

An Indium Arsenide Bismide photodiode has been grown, fabricated, and characterized to evaluate its performance in the Mid Wave Infrared region of the spectrum. Spectral response from the diode has been obtained up to a diode temperature of 225 K. At this temperature, the diode has a cut off wavelength of 3.95 μm, compared to 3.41 μm in a reference Indium Arsenide diode, indicating that Bismuth has been incorporated to reduce the band gap of Indium Arsenide by 75 meV. Similar band gap reduction was deduced from the cut off wavelength comparison at 77 K. From the dark current data, shunt resistance values of 8 and 39 Ω at temperatures of 77 and 290 K, respectively, were obtained in our photodiode.

This work analyses the Bi incorporation in InAs1-xBix/InAs(100) epilayers grown by MBE through advanced transmission electron microscopy techniques. Samples grown from 350–400 °C resulted in Bi contents

The effects of rapid thermal annealing on the optical and structural properties of GaAs1-xBix alloys for x ranging from 0.022 to 0.065 were investigated. At room temperature, the annealed GaAs1-xBix showed modest improvement (∼3 times) in photoluminescence (PL) while the PL peak wavelength remained relatively unchanged. It was found that bismuth related defects are not easily removed by annealing and the PL improvement may be dominated by the reduction of other types of defects including arsenic and gallium related defects. Also, the optimum annealing temperature is Bi composition dependent. For samples with x

Cisapride, a relatively new gastrointestinal prokinetic agent, has been reported to increase gastric emptying and improve symptoms of gastroparesis. We investigated these effects of cisapride in patients with severe idiopathic and diabetic gastroparesis during an eight-week trial. The study design was a two-week single-blind placebo run in period to exclude placebo responders, followed by a six-week randomized, double-blind, placebo-controlled treatment phase. Delayed gastric emptying of solids on radionuclide scan and a minimum symptom intensity score were inclusion criteria. Forty-three patients were entered: four placebo responders and one other patient were excluded, leaving 19 patients randomized to cisapride (20 mg per os three times a day before meals), and 19 patients to placebo. Seven individual symptoms of gastroparesis were scored in a daily diary and reviewed at two-week visits. Sixteen patients in the cisapride group were able to complete the trial compared to 12 on placebo. The gastric emptying study was repeated at the end of treatment or at the time of withdrawal for those who dropped out. Cisapride significantly increased solid gastric emptying relative to baseline (P = 0.005) whereas placebo did not (P > 0.10). Cisapride did not significantly improve any symptom of gastroparesis relative to baseline or to placebo. We conclude that in a population of severe, refractory gastroparetic patients cisapride significantly accelerates gastric emptying of a solid meal without significantly reducing symptoms during a short-term treatment trial compared to placebo. Further trials of cisapride in less advanced and "end-stage" gastroparetics than studied here or combining cisapride with other prokinetic agents or antiemetics, are warranted.