Graphene-All-Around Cobalt Interconnect with a Back-End-of-Line Compatible Process

The graphene-all-around (GAA) structure has been verified to grow directly at 380 °C using hot-wire chemical vapor deposition, within the thermal budget of the back end of the line (BEOL). The cobalt (Co) interconnects with the GAA structure have demonstrated a 10.8% increase in current density, a 27% reduction in resistance, and a 36 times longer electromigration lifetime. X-ray photoelectron spectroscopy and density functional theory calculations have revealed the presence of bonding between carbon and Co, which makes the Co atom more stable to resist external forces. The ability of graphene to act as a diffusion barrier in the GAA structure was confirmed through time-dependent dielectric breakdown measurement. The Co interconnect within the GAA structure exhibits enhanced electrical properties and reliability, which indicates compatibility applications as next-generation interconnect materials in CMOS BEOL.

[Analysis of echocardiographic features and postnatal management of fetal pulmonary valve stenosis]

Objective: To investigate the echocardiographic features, consistency of diagnosis between fetal and postnatal periods and postnatal clinical outcomes of fetal pulmonary valve stenosis (PS) with different degrees. Methods: This study was a retrospective cohort study comprising 108 cases of fetal PS diagnosed during the fetal period and followed up postnatally at Xinhua Hospital, Shanghai Jiaotong University School of Medicine from November 2012 to February 2023. Echocardiographic characteristics, including morphological and hemodynamic features were collected for all fetuses who were then were followed up to at least 6 months after birth. One-way analysis of variance and Kruskal-Wallis test were used to compare the differences in the echocardiographic features among fetuses with different degrees of PS. Subsequently, McNemar test was used to assess the consistency of diagnosis between the fetal and postnatal periods. Furthermore, Logistic regression analysis was applied to explore the risk factors for neonatal intervention in fetuses with moderate PS and the receiver operating characteristic (ROC) curve was utilized to ascertain the optimal cut-off value for continuous variables. Results: The age of the mothers of the 108 fetuses at the initial assessment was (30.8±4.0) years, and the gestational age was 26.5 (24.6, 30.0) weeks. The fetuses were categorized into mild (17 cases), moderate (49 cases), and severe groups (42 cases) based on the initial echocardiographic features. Mild PS was characterized by valve thickening and hyperechogenicity combined with systolic flow acceleration or dilation of main pulmonary artery. Moderate PS exhibited both restricted valve motion and a colorful blood flow pattern at the valve orifice. The peak flow velocities of fetuses with moderate and critical PS were notably higher than those in the mild group ((2.66±0.86) and (2.77±1.30) vs. (1.43±0.59)m/s, F=14.52, P<0.001). In critical PS, all cases showed retrograde ductal flow, with a significantly higher proportion of a small right ventricle compared to the mild and moderate PS (42.9% (18/42) vs. 0 and 2.0% (1/49), χ2=31.73, P<0.001). The proportion of severe tricuspid regurgitation was also higher (35.7% (15/42) vs. 0 and 10.2% (5/49), χ2=36.94, P<0.001). Compared to mild and severe PS, the consistency of diagnosis between fetal and postnatal periods in moderate PS was lower (40.8% (20/49) vs.13/17 and 80.3% (35/42), χ2=12.45, P=0.006). The systolic flow velocity was identified as an independent risk factor for neonatal intervention in fetuses with moderate PS (OR=7.21, 95%CI2.11-24.62). A flow velocity of ≥2.18 m/s in second trimester and ≥3.15 m/s in third trimester indicated the necessity of neonatal intervention for fetal moderate PS. Among the 108 fetuses, 68 underwent surgical intervention and all survived. Additionally, 39 fetuses were regularly followed up. A sole non-surgical fatality occurred, leading to a 6-month survival rate of 99.1% (107/108). Conclusions: Various degrees of fetal PS demonstrate distinctive morphological and hemodynamic alterations in echocardiography. The disparity in severity between the postnatal and fetal stages requires ongoing monitoring for fetal PS. The prognosis for fetal PS is generally favorable.

Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off

Organic radicals have been of interest due to their potential to replace nonradical-based organic emitters, especially for deep-red/near-infrared (NIR) electroluminescence (EL), based on the spin-allowed doublet fluorescence. However, the performance of the radical-based EL devices is limited by low carrier mobility which causes a large efficiency roll-off at high current densities. Here, highly efficient and bright doublet EL devices are reported by combining a thermally activated delayed fluorescence (TADF) host that supports both electron and hole transport and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. Steady-state and transient photophysical studies reveal the optical signatures of doublet luminescence mechanisms arising from both host and guest photoexcitation. The host system presented here allows balanced hole and electron currents, and a high maximum external quantum efficiency (EQE) of 17.4% at 707 nm peak emission with substantially improved efficiency roll-off is reported: over 70% of the maximum EQE (12.2%) is recorded at 10 mA cm-2 , and even at 100 mA cm-2 , nearly 50% of the maximum EQE (8.4%) is maintained. This is an important step in the practical application of organic radicals to NIR light-emitting devices.

Study on the Effects of Quantum Well Location on Optical Characteristics of AlGaN/GaN Light-Emitting HEMT

In this study, AlGaN/GaN light-emitting HEMTs (LE-HEMT) with a single quantum well inserted in different locations in the epitaxy layers are fabricated and analyzed. For both structures, light-emitting originated from electrons in the 2DEG and holes from the p-GaN for radiative recombination is located in the quantum well. To investigate the importance of the location of single quantum well, optical characteristics are compared by simulation and experimental results. The experimental results show that the main light-emitting wavelength is shifted from 365 nm in the UV range to 525 nm in the visible range when the radiative recombination is confined in the quantum well and dominates among other mechanisms. Epi B, which has a quantum well above the AlGaN barrier layer in contrast to Epi A which has a quantum well underneath the barrier, shows better intensity and uniformity in light-emitting. According to the simulation results showing the radiative distribution and electron concentrations for both structures, the lower quantum efficiency is due to the diverse current paths in Epi A. On the other hand, Epi B shows better quantum confinement and therefore better luminescence in the same bias condition, which is consistent with experimental observations. These findings are critical for advancing the performance of LE-HEMTs.

[Outcomes of different types of pulmonary atresia in neonates treated by ductus arteriosus stenting]

Objective: To summarize the outcomes of different types of pulmonary atresia in neonates treated by ductus arteriosus stenting. Methods: This study was a retrospective cohort study. A total of 19 neonates who had pulmonary atresia treated by ductus arteriosus stenting in Xinhua Hospital, Shanghai Jiao Tong University School of Medicine from April 2014 to June 2021 were included. They were divided into the intact ventricular septum (PA-IVS) group and the ventricular septal defect (PA-VSD) group. Ductus arteriosus stents were implanted by different approaches. These children were followed up regularly at the 1, 3, 6, and 12 months after the surgery and annually since then to evaluate the outcome. Independent sample t-test was used for the statistical analysis. Results: There were 12 children in PA-IVS group and 7 in PA-VSD group. All of them were full term in fants. The gestational age of the PA-IVS group and the PA-VSD group was (38.8±1.1) and (37.7±1.8) weeks, the birth weights were (3.2±0.4) and (3.4±1.1) kg, and the age at operation was (10±9) and (12±7) days, respectively, without significant difference (all P>0.05). Among the 12 children with PA-IVS, 9 had stents successfully implanted through the femoral artery and 3 through the femoral vein. Of the 7 children with PA-VSD, 2 had the stents successfully implanted via the femoral artery and 2 failed, and the remaining 3 had stents successfully implanted via the left carotid artery. There was no postoperative thromboembolism, arteriovenous fistula, pseudoaneurysm or other vascular complications. Five children with PA-VSD who had successful operations were followed up at 6 months of age. They all had the operation for pulmonary atresia, repair of the ventricular septal defect, removal of arterial duct stents, and ligation of the arterial duct. All children survived without any stent displacement or stenosis and biventricular circulation was achieved during the follow-up. Conclusions: Ductus arteriosous stenting can be the first-stage treatment for children with PA-IVS and PA-VSD. In addition to the traditional femoral vein and femoral artery approach, the carotid artery can be used as a route for stent placement.

Efficient vertical charge transport in polycrystalline halide perovskites revealed by four-dimensional tracking of charge carriers

Fast diffusion of charge carriers is crucial for efficient charge collection in perovskite solar cells. While lateral transient photoluminescence microscopies have been popularly used to characterize charge diffusion in perovskites, there exists a discrepancy between low diffusion coefficients measured and near-unity charge collection efficiencies achieved in practical solar cells. Here, we reveal hidden microscopic dynamics in halide perovskites through four-dimensional (directions x, y and z and time t) tracking of charge carriers by characterizing out-of-plane diffusion of charge carriers. By combining this approach with confocal microscopy, we discover a strong local heterogeneity of vertical charge diffusivities in a three-dimensional perovskite film, arising from the difference between intragrain and intergrain diffusion. We visualize that most charge carriers are efficiently transported through the direct intragrain pathways or via indirect detours through nearby areas with fast diffusion. The observed anisotropy and heterogeneity of charge carrier diffusion in perovskites rationalize their high performance as shown in real devices. Our work also foresees that further control of polycrystal growth will enable solar cells with micrometres-thick perovskites to achieve both long optical path length and efficient charge collection simultaneously.

Influences of dielectric constant and scan rate on hysteresis effect in perovskite solar cell with simulation and experimental analyses

In this work, perovskite solar cells (PSCs) with different transport layers were fabricated to understand the hysteresis phenomenon under a series of scan rates. The experimental results show that the hysteresis phenomenon would be affected by the dielectric constant of transport layers and scan rate significantly. To explain this, a modified Poisson and drift-diffusion solver coupled with a fully time-dependent ion migration model is developed to analyze how the ion migration affects the performance and hysteresis of PSCs. The modeling results show that the most crucial factor in the hysteresis behavior is the built-in electric field of the perovskite. The non-linear hysteresis curves are demonstrated under different scan rates, and the mechanism of the hysteresis behavior is explained. Additionally, other factors contributing to the degree of hysteresis are determined to be the degree of degradation in the perovskite material, the quality of the perovskite crystal, and the materials of the transport layer, which corresponds to the total ion density, carrier lifetime of perovskite, and the dielectric constant of the transport layer, respectively. Finally, it was found that the dielectric constant of the transport layer is a key factor affecting hysteresis in perovskite solar cells.

Study on the effect of size on InGaN red micro-LEDs

In this research, five sizes (100 × 100, 75 × 75, 50 × 50, 25 × 25, 10 × 10 µm²) of InGaN red micro-light emitting diode (LED) dies are produced using laser-based direct writing and maskless technology. It is observed that with increasing injection current, the smaller the size of the micro-LED, the more obvious the blue shift of the emission wavelength. When the injection current is increased from 0.1 to 1 mA, the emission wavelength of the 10 × 10 μm² micro-LED is shifted from 617.15 to 576.87 nm. The obvious blue shift is attributed to the stress release and high current density injection. Moreover, the output power density is very similar for smaller chip micro-LEDs at the same injection current density. This behavior is different from AlGaInP micro-LEDs. The sidewall defect is more easily repaired by passivation, which is similar to the behavior of blue micro-LEDs. The results indicate that the red InGaN epilayer structure provides an opportunity to realize the full color LEDs fabricated by GaN-based LEDs.

Graphene/SnS2 van der Waals Photodetector with High Photoresponsivity and High Photodetectivity for Broadband 365-2240 nm Detection

The fabrication of graphene/SnS₂ van der Waals photodetectors and their photoelectrical properties are systematically investigated. It was found that a dry transferred graphene/SnS₂ van der Waals heterostructure had a broadband sensing range from ultraviolet (365 nm) to near-infrared (2.24 μm) and respective improved responsivities and photodetectivities of 7.7 × 10³ A/W and 8.9 × 10¹³ jones at 470 nm and 2 A/W and 1.8 × 10¹⁰ jones at 1064 nm. Moreover, positive and negative photoconductance effects were observed when the photodetectors were illuminated by photon sources with energies greater and smaller than the bandgap of SnS₂, respectively. The photoresponsivity (R) versus incident power density (P) follows the empirical law R ∝ P_in^β, with β > -1 for positive photoconductance effects and β < -1 for negative photoconductance effects. On the basis of the Fowler-Nordheim tunneling model and a Poisson and drift-diffusion simulation, we show quantitatively that the barrier height and barrier width of the heterostructure photodetector could be controlled by a laser and an external electrical field through a photogating effect generated by carriers trapped at the interface, which could be used to tune the separation and transport of photogenerated carriers. Our results may be useful for the design of high performance van der Waals heterojunction photodetectors.

Giant gauge factor of Van der Waals material based strain sensors

There is an emergent demand for high-flexibility, high-sensitivity and low-power strain gauges capable of sensing small deformations and vibrations in extreme conditions. Enhancing the gauge factor remains one of the greatest challenges for strain sensors. This is typically limited to below 300 and set when the sensor is fabricated. We report a strategy to tune and enhance the gauge factor of strain sensors based on Van der Waals materials by tuning the carrier mobility and concentration through an interplay of piezoelectric and photoelectric effects. For a SnS2 sensor we report a gauge factor up to 3933, and the ability to tune it over a large range, from 23 to 3933. Results from SnS2, GaSe, GeSe, monolayer WSe2, and monolayer MoSe2 sensors suggest that this is a universal phenomenon for Van der Waals semiconductors. We also provide proof of concept demonstrations by detecting vibrations caused by sound and capturing body movements.

Bistriazoles with a Biphenyl Core Derivative as an Electron-Favorable Bipolar Host of Efficient Blue Phosphorescent Organic Light-Emitting Diodes

High-quality host materials are indispensable for the construction in the emitting layer of efficient organic light-emitting diodes (OLEDs), especially in a guest and host system. The good carrier transport and energy transfer between the host and emitters are out of necessity. In this work, a wide bandgap and bipolar organic compound, 2,2'-bis(4,5-diphenyl-(1,2,4)-triazol-3-yl)biphenyl (BTBP), conjugating two electron-transporting triazole moieties on a hole-transporting biphenyl core, was synthesized and characterized. The wide bandgap of 4.0 eV makes the promise in efficient energy transfer between the host and various color emitters to apply as the universal host, especially for blue emitters. The close electron and hole mobilities perform the same order of 10-5 cm2·V-1·s-1, identified as bipolar behavior and benefited for carrier balance at low bias. Although carrier transportation belongs to bipolar behavior at a low electrical field, the electron mobility is much faster than the hole one at a high electrical field and belongs to electron-transporting behavior. Employing the BTBP as the host matrix mixed with a phosphor dopant, iridium(III)bis[4,6-di-fluorophenyl-pyridinato-N,C2]picolinate, a high-efficiency sky-blue phosphorescent organic light-emitting diode (OLED) was achieved with a maximum current efficiency of 65.9 cd/A, maximum power efficiency of 62.8 lm/W, and maximum external quantum efficiency of 30.2%.

Characterization of semi-polar (20[Formula: see text]1) InGaN microLEDs

In this paper, semi-polar (20[Formula: see text]1) InGaN blue light-emitting diodes (LEDs) were fabricated and compared the performance with those of LEDs grown on c-plane sapphire substrate. LEDs with different chip sizes of 100 μm × 100 μm, 75 μm × 75 μm, 25 μm × 25 μm, and 10 μm × 10 μm were used to study the influence of chip size on the device performance. It was found that the contact behavior between the n electrode and the n-GaN layer for the semi-polar (20[Formula: see text]1) LEDs was different from that for the LEDs grown on the c-plane device. Concerning the device performance, the smaller LEDs provided a larger current density under the same voltage and presented a smaller forward voltage. However, the sidewall's larger surface to volume ratio could affect the IQE. Therefore, the output power density reached the maximum with the 25 μm × 25 μm chip case. In addition, the low blue-shift phenomenon of semi-polar (20[Formula: see text]1) LEDs was obtained. The larger devices exhibited the maximum IQE at a lower current density than the smaller devices, and the IQE had a larger droop as the current density increased for the LEDs grown on c-plane sapphire substrate.

Light Trapping Induced High Short-Circuit Current Density in III-Nitride Nanorods/Si (111) Heterojunction Solar Cells

An effective-area photovoltaic efficiency of 1.27% in power conversion, excluding the grid metal contact area and under 1 sun, AM 1.5G conditions, has been obtained for the p-GaN/i-InGaN/n-GaN diode arrays epitaxially grown on (111)-Si. The short-circuit current density is 14.96 mA/cm2 and the open-circuit voltage is 0.28 V. Enhanced light trapping acquired via multiple reflections within the strain and defect free III-nitride nanorod array structures and the short-wavelength responses boosted by the wide bandgap III-nitride constituents are believed to contribute to the observed enhancements in device performance.

Dependence of carrier escape lifetimes on quantum barrier thickness in InGaN/GaN multiple quantum well photodetectors

We reported significant improvements in device speed by reducing the quantum barrier (QB) thicknesses in the InGaN/GaN multiple quantum well (MQW) photodetectors (PDs). A 3-dB bandwidth of 700 MHz was achieved with a reverse bias of -6 V. Carrier escape lifetimes due to carrier trapping in the quantum wells (QWs) were obtained from both simulation and experimental fitting, identifying carrier trapping as the major speed limiting factor in the InGaN/GaN MQW PDs.

[Efficacy of transcatheter pulmonary valve perforation by micro-guidewire and balloon dilation in neonates with pulmonary atresia with intact ventricular septum]

Objective: To investigate the safety and efficacy of transcatheter perforation of pulmonary valve by micro-guidewire and balloon dilation in the treatment of neonatal pulmonary atresia with intact ventricular septum (PA-IVS). Methods: The retrospective study included 21 neonates (14 males and 7 females) with PA-IVS who underwent transcatheter micro-guidewire pulmonary valve perforation and balloon dilation in Xinhua Hospital from January 2012 to December 2018. All patients underwent the pulmonary valve perforation by micro-guidewire through the Simmons catheter. During the follow-up period at 1, 3, 6, 12 months postoperatively and annually thereafter, the operative efficacy and the development of the right ventricle (RV) were evaluated by echocardiography. Statistical analyses were performed using t test. Results: A total of 21 neonates with PA-IVS were enrolled, and 13 cases were diagnosed prenatally. The median age of surgery was 6 days, the weight was (3.2±0.5) kg. The balloon/valve ratio was 1.19±0.12, and the RV pressure measured by catheter was (121±33) mmHg (1 mmHg=0.133 kPa) . The immediate postoperative RV pressure was (47±13) mmHg. The median follow-up time was 30 months. All the cases enrolled achieved biventricular circulation without death and serious complications. According to the last follow-up data including 16 cases who were followed up for 1 year or longer, the pulmonary artery transvalvular pressure was (29±15) mmHg. The postoperation ratio of right to left ventricular transverse diameter was significantly higher than that before operation (0.86+0.10 vs. 0.73+0.13, t=-2.96, P=0.006). Compared with preoperative data, the postoperation pulmonary valvular diameter Z-score was significantly higher (-1.41±0.89 vs. -2.83±1.06, t=-3.65, P=0.001) and the tricuspid valvular diameter Z-score was significantly higher (-0.52±0.29 vs. -1.34±0.81, t=-3.55, P=0.001). Conclusion: Transcatheter perforation of pulmonary valve by micro-guidewire and balloon dilation is a safe and effective initial therapy for neonatal PA-IVS.

Hybrid classical-quantum linear solver using Noisy Intermediate-Scale Quantum machines

We propose a realistic hybrid classical-quantum linear solver to solve systems of linear equations of a specific type, and demonstrate its feasibility with Qiskit on IBM Q systems. This algorithm makes use of quantum random walk that runs in [Formula: see text](N log(N)) time on a quantum circuit made of [Formula: see text](log(N)) qubits. The input and output are classical data, and so can be easily accessed. It is robust against noise, and ready for implementation in applications such as machine learning.

Different surface plasmon coupling behaviors of a surface Al nanoparticle between TE and TM polarizations in a deep-UV light-emitting diode

The formulations and numerical algorithms of a three-level model for studying the Purcell effect produced by the scattering of an air/AlGaN interface and the surface plasmon (SP) coupling effect induced by a surface Al nanoparticle in a two-polarization emission system to simulate the transverse-electric- (TE-) and transverse-magnetic- (TM-) polarized emissions in an Al_xGa_1-xN/Al_yGa_1-yN (y > x) quantum well (QW) are built. In reasonably selected ranges of Al content for an AlGaN QW to emit deep-ultraviolet (UV) light, the enhancement (suppression) of TE- (TM-) polarized emission is mainly caused by the SP-coupling (interface-scattering) effect. Different from a two two-level model, in the three-level model the TE- and TM-polarized emissions compete for electron in the shared upper state, which is used for simulating the conduction band, such that either interface-scattering or SP-coupling effect becomes weaker. In a quite large range of emission wavelength, in which the intrinsic emission is dominated by TM polarization, with the interface-scattering and SP-coupling effects, the TE-polarized emission becomes dominant for enhancing the light extraction efficiency of a deep-UV light-emitting diode.

Method for enhancing the favored transverse-electric-polarized emission of an AlGaN deep-ultraviolet quantum well

An AlGaN quantum well (QW) structure of a deep-ultraviolet (UV) light-emitting diode (LED) needs to be well designed for controlling its band structure such that the heavy-hole (HH) band edge becomes lower than the split-off (SO) band edge and hence the transverse-electric (TE) polarization dominates the emission for achieving a higher light extraction efficiency. Here, we report the discovery of un-intentionally formed high-Al AlGaN nano-layers right above and below such a QW and their effects on the QW for changing the relative energy levels of the HH and SO bands. The comparison between the results of simulation study and polarization-resolved photoluminescence measurement confirms that the high-Al layers (HALs) represent the key to the observation of the dominating TE-polarized emission. By applying a stress onto a sample along its c-axis to produce a tensile strain in the c-plane for counteracting the HAL effects in changing the band structure, we can further understand the effectiveness of the HALs. The formation of the HALs is attributed to the hydrogen back-etching of Ga atoms during the temperature transition from quantum barrier growth into QW growth and vice versa. The Al filling in the etched vacancies results in the formation of an HAL. This discovery brings us with a simple method for enhancing the favored TE-polarized emission in an AlGaN deep-UV QW LED.

Modeling of carrier transport in organic light emitting diode with random dopant effects by two-dimensional simulation

To model the carrier transport in organic light-emitting diodes (OLEDs) with random dopant effects in the emitting layer, two-dimensional simulation was used. By including the Gaussian shape density of states and field-dependent mobility in the Poisson and drift-diffusion solver, the carrier transport, trapping in the dopant state, and radiative recombination were accurately modeled. To examine the model, the current-voltage characteristics of organic light-emitting devices were compared. The host material in the emitting layer was 2,2-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)biphenyl (BImBP), which was doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) at various concentrations. By including the random doping model, the trend of mobility was altered and the radiative efficiency fitted experimental values well.

[Population genomic researches of Escherichia coli]

Population genomics, an interdiscipline of genomics and population genetics, is booming in recent years with the rapid growth number of deciphered genomes and revolutionizes the understanding of bacterial population diversity and evolution dynamics. It also largely improves the prevention and control of infectious disease through providing more accurate genotyping and source-tracing results and more comprehensive characteristics of emerging pathogens. In this review, taking one of the best characterized bacteria, Escherichia coli, as model, we reviewed the phylogenetic relationship across its five major populations (designated A, B1, B2, D and E); and summarized researches on molecular mutation rate, selection signals, and patterns of adaptive evolution. We also described the application of population genomics in responding against large-scale outbreaks of E. coli O157:H7 and E. coli O104:H4. These results indicated that, although being a novel discipline, population genomics has played an important role in deciphering bacterial population structures, exploring evolutionary patterns and combating emerging infectious diseases.

Modeling and optimization of p-AlGaN super lattice structure as the p-contact and transparent layer in AlGaN UVLEDs

A series of the p-Al(x)Ga(1-x)N/Al(y)Ga(1-y)N super lattice (SL) structures has been examined as the p-contact and transparent layer for different ultra-violet light-emitting-diodes (UVLEDs) with a self-consistent 1D Poisson and Schrödinger solver. The recommended solution for designing the suitable SL structure in UVLEDs with different UV wavelength has been found. By calculating the absorption coefficient of the SL structure, we confirmed that the proper SL structure has the enormous potential of being the transparent p-contact layer in AlGaN UVLED, especially in UV-C band (< 280 nm). The suitable emission wavelengths of UVLEDs ranging from 219 nm to 353 nm are found. The influences of different well and barrier thickness on SL structures are discussed as well.

Photoelectrochemical hydrogen generation with linear gradient Al composition dodecagon faceted AlGaN/n-GaN electrode

We demonstrated photoelectrochemical cells (PECs) with dodecagon faceted AlGaN/n-GaN heterostructure electrode for H(2) generation, where the AlGaN/n-GaN heterostructure has a linear gradient Al composition (LGAC). The separation efficiency of the photo-generated electron-hole pairs in the electrode performs a key function in the H(2) generation efficiency of PEC cells. The linear gradient Al composition, AlGaN, could create more internal field and light absorption because of the linear graded band gap. Therefore, the zero-bias photocurrent density of PEC cells with dodecagon facet LGAC AlGaN/n-GaN heterostructure electrode is around 5.9 times larger than that of dodecagon faceted n-GaN electrode.

Efficiency dip observed with InGaN-based multiple quantum well solar cells

The dip of external quantum efficiency (EQE) is observed on In(0.15)Ga(0.85)N/GaN multiple quantum well (MQW) solar cells upon the increase of incident optical power density. With indium composition increased to 25%, the EQE dip becomes much less noticeable. The composition dependence of EQE dip is ascribed to the competition between radiative recombination and photocurrent generation in the active region, which are dictated by quantum-confined Stark effect (QCSE) and composition fluctuation in the MQWs.

Investigation of the strain induced optical transition energy shift of the GaN nanorod light emitting diode arrays

Strain in the semiconductor light emitting layers has profound effect on the energy band structure and the optical properties of the light emitting diodes (LEDs). Here, we report the fabrication and characterization of GaN nanorod LED arrays. We found that the choice of nanorod passivation materials results in the variation of strain in the InGaN/GaN quantum wells, and thus the corresponding change of light emission properties. The results were further investigated by performing Raman measurement to understand the strain of nanorods with different passivation materials and by calculating the optical transition energy of the devices under the influence of strain-induced deformation potential and the piezoelectric polarization field.

Acute disseminated encephalomyelitis that meets modified McDonald criteria for dissemination in space is associated with a high probability of conversion to multiple sclerosis in Taiwanese patients

BACKGROUND

Patients with acute disseminated encephalomyelitis (ADEM) may relapse and some may ultimately convert to multiple sclerosis (MS); however, no criteria that can predict MS conversion are available to date. Our aim was to describe the clinical and magnetic resonance imaging (MRI) features of patients with an initial ADEM attack and evaluate which MRI criteria can predict conversion to MS.

METHODS

We retrospectively reviewed the records of 36 patients diagnosed with ADEM. We determined clinical signs/symptoms, examined the cerebrospinal fluid (CSF), and performed brain MRI scans and compared the findings between patients who did and did not convert to MS.

RESULTS

Clinical signs/symptoms, and CSF analysis show no significant difference between the two groups. The rate of conversion to MS from ADEM in Taiwanese patients is low (11%) after a mean follow-up period of 28.36 months. Modified McDonald criteria were fulfilled in 19/36 patients: 21% (4/19) of those patients developed MS according to Poser criteria subsequently. Of the other patients (17/36) who did not fulfill these criteria, none converted to MS. (log rank test; P=0.027).

CONCLUSIONS

It is difficult to predict from initial clinical presentations to address which patients with ADEM will convert to MS. Patients with ADEM whose brain MRI findings met the modified McDonald criteria may have clinically isolated syndrome because they have a significantly higher probability of conversion to MS. In contrast, patients whose brain MRI findings did not meeting these criteria may be considered as having classic ADEM because they have a lower probability of conversion to MS.

Abnormal polarization switching phenomenon in a-plane AlxGa(1-)xN

The optical polarization properties of a-plane AlxGa(1-)xN films have been investigated by polarization-dependent photoluminescence (PL). The degree of polarization decreased with increasing the Al composition, and the main optical polarization direction switched from ε ⊥ cto ε // c at about x = 0.07 due to the valence band switching, representing that the optical transition energy of ε // c is surpassing that of ε ⊥ c. However, with the Al composition larger than x = 0.1, the higher energy optical transitions of ε // cexhibited the stronger PL intensity, opposite to the normal situations that higher energy states commonly have weaker PL intensity than the lower energy states. We utilized the 6 × 6 k.p model and the lambertian-like radiation pattern assumption to explain this abnormal optical polarization switching behavior in the a-plane AlxGa(1-)xN layers and obtained good agreement with the experimental results.

Analysis of the UCHL1 genetic variant in Parkinson's disease among Chinese

The inverse association of the functional ubiquitin carboxy-terminal hydrolase L1 (UCHL1) S18Y variant with Parkinson's disease (PD) among Caucasian populations has been debated. We conducted a large-scale analysis to investigate the age-of-onset effect of the UCHL1 variant in PD among ethnic Chinese. Individual data sets from 5 centers comprising a total of 4088 study subjects were analyzed. In the univariate analysis, only data from 1 center showed a trend towards a protective effect among young subjects. However, in the combined analysis, no significant association between the UCHL1 variant and PD was detected (A allele frequency 0.531 vs. 0.528, p=0.87, OR 1.01, 95% CI 0.92-1.1). Among subjects less than 60 years old, the OR is 0.99 (95% CI 0.84-1.16, p=0.88). A multivariate logistic regression analysis showed that family history, UCHL1 variant and the interaction of UCHL1 variant and age at onset (p=0.816) were not significantly associated with PD.

Clinical features, vascular risk factors, and prognosis for transient global amnesia in Chinese patients

BACKGROUND

Transient global amnesia (TGA) is an intriguing clinical syndrome that has not been studied in a series of Chinese patients.

METHODS

From 1989 to 1995, we observed 28 consecutive patients with TGA. Their clinical characteristics, risk factors, and outcome were retrospectively reviewed and analyzed.

RESULTS

There were 13 men and 15 women with a mean age of 62 years (range, 39 to 76). The duration of amnesic attack ranged from 20 minutes to 24 hours (mean, 8 hours), with the majority (76%) of attacks lasting for 2 to 12 hours. In 9 (32%) of the 28 patients, the TGA was triggered by a potential precipitating factor including bathing, emotional stress, and headache. The most prominent symptom exhibited by patients during an attack was repetitive questioning, which occurred in 21 (75%) of the 28 patients. No focal neurological abnormality was noted during or after the attack. Electroencephalograms were obtained in 26 patients after experiencing TGA, which showed nonspecific findings in 6 patients and were normal in 20. In 21 patients who had cranial computed tomography scans, cortical atrophy was found in 5 (24%), focal infarction in 4 (19%), and the results were negative in 12 (57%). Hypertension was the predominant vascular risk factor (11 cases, 39%), then hyperlipidemia (7 cases, 25%), and smoking (3 cases, 11%). No vascular risk factor was found in 13 patients (46%). Recurrent TGA was found in 5 patients (18%), and stroke in 2 (7%).

CONCLUSION

Our study largely confirms the demographic pattern, clinical characteristics, and prognosis of TGA patients reported from the western countries. Although the cause is uncertain, TGA is a relatively benign entity.

Interleukin-1 alpha polymorphism has influence on late-onset sporadic Parkinson's disease in Taiwan

Inflammatory events may contribute to the pathogenesis of Parkinson's disease (PD) and interleukin 1 (IL-1) may exert both neurotoxic and neuroprotective effects. We conducted a case-control study in a cohort of 493 PD cases and 388 ethnically matched controls to investigate the association of IL-1alpha C-889T and IL-1beta C-511T polymorphisms with the risk of PD. No significant difference in the genotype distribution of the analyzed polymorphisms was found between PD and controls. However, after stratification by age, individuals over 70 years of age carrying IL-1alpha-889 C/T genotype demonstrated a significant decrease in risk of developing PD (OR = 0.44; 95% CI = 0.22-0.88, p = 0.021) and the decrease is strengthened by IL-1beta-511 T-carrying genotype (OR = 0.28; 95% CI = 0.11-0.71, p = 0.008). Our data suggest that IL-1alpha, acting synergistically with IL-1beta, plays role in PD susceptibility among Taiwanese people older than 70 years of age.

Mitochondrial DNA polymorphisms and the risk of Parkinson's disease in Taiwan

A critical role of mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD). The association of mitochondrial DNA (mtDNA) polymorphisms 9055G/A, 10398G/A and 13708G/A with PD has been controversial. In this study we analyzed whether these three genetic polymorphisms are associated with PD in a cohort of 416 PD cases and 372 ethnically matched controls. The allele frequency distribution of any of these three analyzed polymorphisms was not significantly different between the cases and the controls. None of the six haplotypes derived influences risk of PD. Notably, after stratification by age, individuals over 70 years of age carrying the haplotype 9055G-10398A-13708G demonstrated a significant decrease in risk of developing PD (OR = 0.44, 95% CI = 0.24-0.80, p = 0.008). These results suggest that the mtDNA haplotype 9055G-10398A-13708G plays a role in PD susceptibility among Taiwanese people older than 70 years of age.

Association of tau haplotype-tagging polymorphisms with Parkinson's disease in diverse ethnic Parkinson's disease cohorts

BACKGROUND

The overlap in the clinical and pathological features of tauopathies and synucleinopathies raises the possibility that the tau protein may be important in Parkinson's disease (PD) pathogenesis. Several MAPT polymorphisms that define the tau H1 haplotype have been investigated for an association with PD with conflicting results; however, two meta-analyses support an association between haplotype H1 and PD.

METHODS

In this study, we recruited 508 patients and 611 healthy controls from Greek, Finnish and Taiwanese populations. We examined the possible genetic role of variation within MAPT in PD using haplotype-tagging single polymorphisms (SNPs) in these ethnically different PD populations.

RESULTS

We identified a moderate association at SNP rs3785883 in the Greek cohort for both allele and genotype frequency (p = 0.01, p = 0.05, respectively) as well as for SNP rs7521 (genotype p = 0.02) and rs242557 (p = 0.01 genotypic, p = 0.04 allelic) in the Finnish population. There were no significant differences in genotype or allele distribution between cases and controls in the Taiwanese cohort.

CONCLUSION

We failed to demonstrate a consistent association between the MAPT H1 haplotype (delineated by intron 9 ins/del) and PD in three ethnically diverse populations. However, the data presented here suggest that subhaplotypes of haplotype H1 may confer susceptibility to PD, and that either allelic heterogeneity or different haplotype composition explain the divergent haplotype results.

Clinical characteristics of multiple sclerosis in Taiwan: a cross-sectional study

This study reviewed the clinical characteristics of multiple sclerosis (MS) in Taiwanese patients from 1993 to 2001. Of the 75 MS patients with a mean age of onset of 35.6 +/- 12.6 years, the female-to-male ratio was 4.4 (61/14). In 42 (56%) optico-spinal MS (OS-MS) patients, the age of onset (37.6 +/- 11.1 years) tended to be older than conventional MS (C-MS) patients (33.1 +/- 14.1 years, P = 0.08). In 60 cerebrospinal fluid (CSF) specimens, raised IgG index (>0.7) and oligoclonal bands were noted in 26 (43.3%) and two (3.3%) cases, respectively. The frequency of raised IgG index was lower in OS-MS (31.3%) than in C-MS (57.1%, P = 0.07). The CSF total protein concentrations were significantly higher in OS-MS (64.5 mg/dL) than in C-MS (46.6 mg/dL, P = 0.047). The mean annual relapse rate was 54.1%, and was significantly higher within the first year (59.7%, P < 0.001). The mean annual relapse rate in OS-MS (62.7%) was significantly higher than in C-MS (41.2%, P=0.01). The differences in the annual relapse rate and total protein concentration in CSF between OS-MS and C-MS suggest probably two distinct immunopathogenesis. The higher first year relapse rate of MS patients in Taiwan may address the importance of early intervention with immunomodulatory therapy.

α-Synuclein promoter RsaI T-to-C polymorphism and the risk of Parkinson’s disease

Increased alpha-synuclein expression may be involved in the pathogenesis of Parkinson's disease (PD). We investigated the association of Rep1 microsatellite and RsaI T-to-C substitution in the alpha-synuclein promoter region with the risk of PD by a case-control study. The RsaI C/C genotype and C allele were found less frequently in PD patients than in controls. A reduced risk of the Rep1-RsaI 0-C haplotype (OR = 0.57, 95% CI = 0.36-0.90) with PD was evident. The quantitative real-time PCR study showed that the alpha-synuclein mRNA expression was increased (although not significantly) in PD patients with RsaI T/T genotype or Rep1-RsaI 0-T haplotype as compared to T/C genotype or 0-C haplotype. Reporter constructs containing the RsaI C allele drove significantly lower transcriptional activity compared with the RsaI T allele in both IMR32 and 293 cells. The findings suggest that the RsaI T-to-C substitution may have a functional relevance to the susceptibility to PD.

Apolipoprotein E, angiotensin-converting enzyme and kallikrein gene polymorphisms and the risk of Alzheimer's disease and vascular dementia

Lipoproteins and vascular factors may play roles in the development of Alzheimer's disease (AD) and/or vascular dementia (VaD). In this study, odd ratios (ORs) and 95% confidence intervals (CIs) for apolipoprotein E (APOE), angiotensin-converting enzyme (ACE), and kallikrein (KLK1) polymorphisms were computed to test their association with the disease by a case-control study. The risk of AD was significantly increased for individuals with APOE varepsilon4 allele (OR = 3.73, 95% CI = 2.38-5.98). The risk of AD was also significant for people with ACE DD genotype, D allele, or T-D haplotype [OR (95% CI) = 4.29 (1.96-10.23), 1.90 (1.35-2.70), or 2.91 (1.71-5.10), respectively]. The above association between ACE-VaD was also strong (p = 0.0012, 0.0050, 0.0007, respectively). Reporter constructs containing the -240 A or T allele displayed similar transcriptional activity in both HEK-293 and IMR-32 cells. Thus, another putative pathogenic marker that is linked with the Alu D allele might affect the risk of AD and VaD in Taiwan.

Heat shock protein 70 and tumor necrosis factor alpha in Taiwanese patients with dementia

This study was to determine whether polymorphisms of heat shock protein 70-1 (HSP70-1) and tumor necrosis factor alpha (TNF-alpha) are associated with the risk of Alzheimer's disease (AD) and vascular dementia (VaD). Using the criteria of the NINCDS-ADRDA and NINDS-AIREN, 125 AD patients, 57 VaD patients and 109 ethnically matched nondemented controls were enrolled. The HSP70-1 -110 A/C and TNF-alpha -1031 T/C, -863 C/A and -857 C/T polymorphisms were analyzed by means of genotype or haplotype association methods. None of the four genotypes examined showed a statistically significant difference in genotype distribution between the AD cases and controls. However, the HSP70-1 -110 CC genotype occurred more frequently among AD cases (p=0.0821; odds ratio: 2.08; 95% confidence interval, CI: 0.92-4.98). The overall genotype distribution among the VaD cases tended to be different at the HSP70-1 -110 and TNF-alpha -1031 sites (p=0.0604 and 0.0316, respectively). The HSP70-1 -110 CC genotype was more frequent (p=0.0459), and the association of the -110 CC genotype with VaD was evident (p=0.0207; odds ratio: 3.22; 95% CI: 1.20-8.87). The more frequent TNF-alpha -1031 TC genotype (p=0.0614) was also evidently associated with VaD (p=0.0209; odds ratio: 2.32; 95% CI: 1.14-4.78). Multivariate analysis demonstrated the synergistic effect of the HSP70-1 -110 CC and TNF-alpha -1031 TC/CC genotypes on VaD (p=0.0091; odds ratio: 10.09; 95% CI: 2.01-75.97). Haplotype analysis among TNF-alpha -1031, -863, -857 sites revealed that -1031C-857C may act as a risk haplotype among VaD cases (p=0.0132, odds ratio: 2.26; 95% CI: 1.19-4.33). Our results suggest a potential protective role for HSP70 in both VaD and AD, whereas TNF-alpha may act as a risk factor only for VaD, and not for AD.

Analysis of polyglutamine-coding repeats in the TATA-binding protein in different neurodegenerative diseases

Trinucleotide repeat (TNR) expansion in the gene for TATA binding protein (TBP) has recently been described as causal for spinocerebellar ataxia type 17. The normal number of repeats has been considered to be 42 or less. An intermediate range with reduced penetrance has been assumed to be 43-47 CAA/CAG repeats. We examined this gene in 30 patients with autosomal-dominant cerebellar ataxia (ADCA), 35 patients with sporadic ataxia, 11 patients with Huntington's disease (HD), 351 patients with idiopathic Parkinson's disease (PD), 105 patients with Alzheimer's disease (AD), and 291 controls with no history of neurodegenerative disease. Three patients (one with sporadic PD and two with AD) carrying more than 42 TNRs in the TBP gene were identified. This reveals that the phenotype associated with CAG/CAA expansion in the TBP gene may be heterogeneous.

DNA haplotype analysis of CAG repeat in Taiwanese Huntington's disease patients

We studied the expanded CAG repeat and adjacent CCG repeat in 53 Huntington's disease (HD) patients and 172 unrelated normal subjects matched to the patients for ethnic origin. The range of the CAG repeat varied from 38 to 109 in the HD patients and from 10 to 29 in the control group. A significant negative correlation was found between the age at onset and the CAG expansion, with no significant influence of the adjacent CCG repeat on the age at onset by multiple regression analysis. Allelic association using CCG repeat and 2 flanking dinucleotide repeat markers within 150 kb of the HD gene revealed linkage disequilibrium for 2 of 3 markers. Haplotype analysis of 24 HD families using these markers identified 3 major haplotypes underlying 87.5% of HD chromosomes. The data suggested frequent haplotypes in the Taiwanese population on which one or more mutational events leading to the disease occurred.

The use of evoked potentials for clinical correlation and surgical outcome in cervical spondylotic myelopathy with intramedullary high signal intensity on MRI

OBJECTIVE

To investigate the use of motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) for clinical significance and surgical outcome in patients with cervical spondylotic myelopathy (CSM) with intramedullary high signal intensity on T2 weighted MRI.

METHODS

Forty nine patients were scored according to the modified Japanese Orthopaedic Association (JOA) score for cervical myelopathy. MEP and SEP studies were performed and the results were categorised as normal or abnormal. Thirty nine patients who had received surgical decompression were re-evaluated after 6 months. Surgical outcome was represented by the recovery ratio of the JOA score.

RESULTS

Abnormal MEPs were observed in 44 patients (arm: 43; leg: 30). Abnormal SEPs were found in 32 patients: (median: 24; tibial: 23). Patients with abnormal SEPs had a worse JOA score than those with normal SEPs. Thirty nine patients received surgical treatment. Patients younger than 55 had better recovery ratios than those who were 55 or older (p = 0.005, two sample Student's t test). Patients with normal median SEPs also had better recovery ratios than those with abnormal median SEPs (p = 0.007, two sample Student's t test). Among median SEP variables, only N9-20 was significantly associated with recovery ratio (p = 0.016, stepwise linear regression), with age factor controlled (p = 0.025, stepwise linear regression).

CONCLUSION

Arm MEP was the most sensitive EP test for detecting myelopathy in patients with chronic CSM. Median and tibial SEPs correlated well with the severity of myelopathy while normal median SEPs correlated with good surgical outcome. Among median SEP variables, only N9-20 correlated with surgical outcome.

Genetic testing in spinocerebellar ataxia in Taiwan: expansions of trinucleotide repeats in SCA8 and SCA17 are associated with typical Parkinson's disease

DNA tests in normal subjects and patients with ataxia and Parkinson's disease (PD) were carried out to assess the frequency of spinocerebellar ataxia (SCA) and to document the distribution of SCA mutations underlying ethnic Chinese in Taiwan. MJD/SCA3 (46%) was the most common autosomal dominant SCA in the Taiwanese cohort, followed by SCA6 (18%) and SCA1 (3%). No expansions of SCA types 2, 10, 12, or dentatorubropallidoluysian atrophy (DRPLA) were detected. The clinical phenotypes of these affected SCA patients were very heterogeneous. All of them showed clinical symptoms of cerebellar ataxia, with or without other associated features. The frequencies of large normal alleles are closely associated with the prevalence of SCA1, SCA2, MJD/SCA3, SCA6, and DRPLA among Taiwanese, Japanese, and Caucasians. Interestingly, abnormal expansions of SCA8 and SCA17 genes were detected in patients with PD. The clinical presentation for these patients is typical of idiopathic PD with the following characteristics: late onset of disease, resting tremor in the limbs, rigidity, bradykinesia, and a good response to levodopa. This study appears to be the first report describing the PD phenotype in association with an expanded allele in the TATA-binding protein gene and suggests that SCA8 may also be a cause of typical PD.

Mapping QTLs and candidate genes for rice root traits under different water-supply conditions and comparative analysis across three populations

To investigate the genetic factors underlying constitutive and adaptive morphological traits of roots under different water-supply conditions, a recombinant inbred line (RIL) population derived from a cross between the lowland rice variety IR1552 and the upland rice variety Azucena with 249 molecular markers, was used in cylindrical-pot experiments. Eighteen QTLs were detected for seminal root length (SRL), adventitious root number (ARN), and lateral root length (LRL) and lateral root number (LRN) on the seminal root at a soil depth of from 3 to 6 cm under flooding and upland conditions. One identical QTL was detected under both flooding and upland conditions. The relative parameters under the two water-supply conditions were also used for QTL analysis. Five QTLs for upland induced variations in the traits were detected with the positive alleles from Azucena. A comparative analysis was performed for the QTLs detected in this study and those reported from two other populations with Azucena as a parent. Several identical QTLs for root elongation were found across the three populations with positive alleles from Azucena. Candidate genes were screened from ESTs and cDNA-AFLP clones for comparative mapping with the detected QTLs. Two genes for cell expansion, OsEXP2 and endo-1,4-beta-D-glucanase EGase, and four cDNA-AFLP clones from root tissues of Azucena, were mapped on the intervals carrying the QTLs for SRL and LRL under upland conditions, respectively.

Does stimulation of the GPi control dyskinesia by activating inhibitory axons?

A 69-year-old woman with Parkinson's disease and levodopa-induced dyskinesias had a deep brain stimulation (DBS) electrode inserted into the right globus pallidus internus (GPi). During the operation, the GPi was mapped with dual microelectrode recordings. Stimulation through one microelectrode in GPi inhibited the firing of GPi neurons recorded with another microelectrode 600--1,000 microm distant. The inhibition could be obtained with pulse widths of 150 micros and intensities as low as 10 microA. Single stimuli inhibited GPi neurons for approximately 50 ms. Trains of 300 Hz stimuli inhibited GPi neuron firing almost completely. Postoperatively, stimulation through macroelectrode contacts located in the posterior ventral pallidum controlled the patient's dyskinesias. The effect could be obtained with pulse widths of 50 micros and frequencies as low as 70--80 Hz. We postulate stimulation of the ventral pallidum controls dyskinesias by activating large axons which inhibit GPi neurons.

Orthostatic tremor arises from an oscillator in the posterior fossa

We tested the hypotheses that orthostatic tremor is generated by a central oscillator and that the tremor is expressed through spinal Ib interneurons. Six patients with orthostatic tremor were examined. The tremor was reset by electrical stimulation over the posterior fossa at intensities that were below the threshold for a motor evoked potential (MEP) but was not reset by transcranial magnetic stimulation over the motor cortex that did produce an MEP. It is argued that the oscillator involves the cerebellum or brainstem. The inhibition of voluntary EMG produced by stimulation over tendons, which has been attributed to effects from Golgi tendon organs (GTO), was not modulated in synchrony with the tremor. We were unable to demonstrate, therefore, that the tremor is expressed through GTO interneurons with this method.

Haemophilus influenzae meningitis in adults

Haemophilus influenzae meningitis is rare in adults. We reviewed the microbiological records of cerebrospinal fluid (CSF) and blood cultures and the medical records of patients with bacterial meningitis admitted to Chang Gung Memorial Hospital from January 1978 to May 1996. Haemophilus influenzae meningitis was found in six adult patients, accounting for 1.8% of 326 bacteriologically proven adult cases of meningitis diagnosed between January 1984 and May 1996. Predisposing conditions included head trauma and/or neurosurgical procedure in four patients and an extracranial extension of a pituitary adenoma in a diabetic patient. None of them had altered consciousness on the day of treatment. A CSF cell count less than 500 x 10(6) leukocytes/liter was noted in three patients. Antibiotic therapy was successful in all patients. Thus, predisposing conditions, particularly head trauma and/or neurosurgical procedure, are commonly present in adult patients with H. influenzae meningitis. Patients with the infection may have a low cellular count in the CSF that may be readily misinterpreted as meningitis caused by other pathogens.

Vocal cord paralysis as an initial sign of multiple system atrophy in the central nervous system

Multiple system atrophy (MSA) of the central nervous system has been recognized as a rare cause of stridor secondary to vocal cord paralysis. This respiratory problem usually occurs in the later stages of the disease. We report the case of a 53-year-old man who presented with bilateral vocal cord paralysis accompanied by stridor and sleep apnea, which were relieved by a tracheostomy. Two years after the onset of stridor, he developed extrapyramidal and cerebellar signs combined with severe autonomic failure. Magnetic resonance imaging of the brain revealed atrophy of the brainstem and cerebellum. This clinical picture is consistent with the diagnosis of MSA. Vocal cord paralysis preceding any other neurologic and autonomic manifestations has been infrequently described. This case should remind clinicians that MSA should be considered in the differential diagnosis of vocal cord palsy of undetermined origin.

Case report: Pontine haemorrhage following iohexol lumbar myelography

A case of pontine haemorrhage following lumbar myelography using iohexol is described. Stress, inducing transient hypertension during the procedure, with superimposed neurotoxicity from contrast medium (iohexol) is suggested as a possible mechanism. No brain stem lesion was seen on the initial brain CT scan, possibly because of the high attenuation of the contrast medium in the subarachnoid space. A delayed CT brain scan demonstrated the pontine haemorrhage and was necessary to confirm the diagnosis.