To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Background: SMA is a neurodegenerative disease caused by biallelic deletion/mutation of SMN1. Copies of a similar gene (SMN2) modify disease severity. In a phase 1 study, SMN GRT onasemnogene abeparvovec (AVXS-101) improved outcomes of symptomatic SMA patients with two SMN2 copies (2xSMN2) dosed ≤6 months. Because motor neuron loss can be insidious and disease progression is rapid, early intervention is critical. This study evaluates AVXS-101 in presymptomatic SMA newborns. Methods: SPR1NT is a multicenter, open-label, phase 3 study enrolling ≥27 SMA patients with 2–3xSMN2. Asymptomatic infants ≤6 weeks receive a one-time intravenous AVXS-101 infusion (1.1x1014 vg/kg). Safety and efficacy are assessed through study end (18 [2xSMN2] or 24 months [3xSMN2]). Primary outcomes: independent sitting for ≥30 seconds (18 months [2xSMN2]) or assisted standing (24 months [3xSMN2]). Results: From April–September 2018, 7 infants received AVXS-101 (4 female; 6 with 2xSMN2) at ages 8–37 days. Mean baseline CHOP-INTEND score was 41.7 (n=6), which increased by 6.8, 11.0, 18.0, and 22.5 points at day 14 (n=4), month 1 (n=3), 2 (n=3), and 3 (n=2). Updated data available at the time of the congress will be presented. Conclusions: Preliminary data from SPR1NT show rapid motor function improvements in presymptomatic SMA patients.
Prediction of suicidal behaviour is an aspirational goal for clinicians and policy makers; with patients classified as ‘high risk’ to be preferentially allocated treatment. Clinical usefulness requires an adequate positive predictive value (PPV).
To identify studies of predictive instruments and to calculate PPV estimates for suicidal behaviours.
A systematic review identified studies of predictive instruments. A series of meta-analyses produced pooled estimates of PPV for suicidal behaviours.
For all scales combined, the pooled PPVs were: suicide 5.5% (95% CI 3.9–7.9%), self-harm 26.3% (95% CI 21.8–31.3%) and self-harm plus suicide 35.9% (95% CI 25.8–47.4%). Subanalyses on self-harm found pooled PPVs of 16.1% (95% CI 11.3–22.3%) for high-quality studies, 32.5% (95% CI 26.1–39.6%) for hospital-treated self-harm and 26.8% (95% CI 19.5–35.6%) for psychiatric in-patients.
No ‘high-risk’ classification was clinically useful. Prevalence imposes a ceiling on PPV. Treatment should reduce exposure to modifiable risk factors and offer effective interventions for selected subpopulations and unselected clinical populations.
14C measured in trace gases in clean air helps to determine the sources of such gases, their long-range transport in the atmosphere, and their exchange with other carbon cycle reservoirs. In order to separate sources, transport and exchange, it is necessary to interpret measurements using models of these processes. We present atmospheric 14CO2 measurements made in New Zealand since 1954 and at various Pacific Ocean sites for shorter periods. We analyze these for latitudinal and seasonal variation, the latter being consistent with a seasonally varying exchange rate between the stratosphere and troposphere. The observed seasonal cycle does not agree with that predicted by a zonally averaged global circulation model. We discuss recent accelerator mass spectrometry measurements of atmospheric 14CH4 and the problems involved in determining the fossil fuel methane source. Current data imply a fossil carbon contribution of ca 25%, and the major sources of uncertainty in this number are the uncertainty in the nuclear power source of 14CH4, and in the measured value for δ14C in atmospheric methane.
This study aimed to identify genetic evaluation models (GEM) to accurately select cattle for milk production when only limited data are available. It is based on a data set from the Pakistani Sahiwal progeny testing programme which includes records from five government herds, each consisting of 100 to 350 animals, with lactation records dating back to 1968. Different types of GEM were compared, namely: (1) multivariate v. repeatability model when using the first three lactations, (2) an animal v. a sire model, (3) different fixed effects models to account for effects such as herd, year and season; and (4) fitting a model with genetic parameters fixed v. estimating the genetic parameters as part of the model fitting process. Two methods were used for the comparison of models. The first method used simulated data based on the Pakistani progeny testing system and compared estimated breeding values with true breeding values. The second method used cross-validation to determine the best model in subsets of actual Australian herd-recorded data. Subsets were chosen to reflect the Pakistani data in terms of herd size and number of herds. Based on the simulation and the cross-validation method, the multivariate animal model using fixed genetic parameters was generally the superior GEM, but problems arise in determining suitable values for fixing the parameters. Using mean square error of prediction, the best fixed effects structure could not be conclusively determined. The simulation method indicated the simplest fixed effects structure to be superior whereas in contrast, the cross-validation method on actual data concluded that the most complex one was the best. In conclusion it is difficult to propose a universally best GEM that can be used in any data set of this size. However, some general recommendations are that it is more appropriate to estimate the genetic parameters when evaluating for selection purposes, the animal model was superior to the sire model and that in the Pakistani situation the repeatability model is more suitable than a multivariate.
The incorporation of oxygen onto the (3×3) reconstructed surface of GaN(0001) has been studied using X-ray Photoelectron Spectroscopy (XPS). It was found that the (3×3) reconstruction corresponds to a fractional Ga adlayer atop a Ga terminated GaN surface. Our measurements indicate a surface coverage of 1.15 ± 0.2 monolayers of relaxed Ga on the surface. The binding energy separation between the relaxed surface Ga3d core level and bulk Ga3d level was measured to be 1.1 ± 0.1 eV. A metallic component extending from the bulk GaN valence band maximum out to 0 eV was also present in the XPS spectrum. The separation between the bulk valence band maximum and the Fermi level of the metallic component was found to be 2.1 ± 0.1 eV. The relaxation of the surface Ga was found to decrease with oxygen exposure indicating Ga-O bonding, with oxygen adsorption terminating at 1.3 ± 0.2 monolayers. The O1s core level was found to have a FWHM of 2.0 ± 0.1 eV.
Hairy polyps are rare congenital growths of the head and neck, mainly found in the nasopharynx and oropharynx. They are made up of two germ cell layers: the ectoderm and mesoderm.
This paper reports a four-month-old who presented with breathing and feeding difficulties. Clinical examination was unremarkable, but a video taken by the patient's mother on her smartphone showed a mass protruding from the infant's mouth. Laryngoscopy performed in the operating theatre showed that the mass emanated from the left posterior tonsillar pillar.
The mass was removed transorally with no complications. Pathological examination showed a skin-covered pedunculated structure characteristic of a hairy polyp. The patient's follow up was unremarkable.
To the best of our knowledge, this is the second English-language case report of a patient with a hairy polyp emanating from a posterior tonsillar pillar. This paper also highlights the growing usage of smartphones by patients to help physicians with their diagnosis and management.
We are developing a new non-contact and non-destructive imaging technique which requires no sample preparation and provides similar content information as FTIR or Raman spectroscopy while being immune to fluorescence and offers a potentially faster scan rate and/or higher spatial resolution. It utilizes photo-thermal heating of the sample with a quantum cascade laser (or other suitable infrared laser) and measuring the resulting increase in thermal emissions by either an infrared (IR) detector or a laser probe consisting of a visible laser reflected from the sample. The latter case allows for further increases in the spatial resolution from ∼10 μm to ∼1 μm or better, with suitable experimental conditions. Since the thermal emission signal is proportional to the absorption coefficient, by tuning the wavelength of the IR laser we can directly measure the IR spectrum of the sample. By raster scanning over the surface of the sample we can obtain maps of the chemical composition of the sample surface. We demonstrate this technique by imaging the surface of a micro-fabricated flow-through chemical vapor preconcentrator consisting of a silicon frame and a suspended-perforated polyimide membrane with a pair of platinum heater traces, coated with a custom sorbent polymer for selective sorption of analyte. We measure the spatial resolution of our photo-thermal imaging system as well as discuss the conditions under which the spatial resolution can be further increased from the far-field diffraction limited resolution given by the combination of the imaging optic and IR excitation laser wavelength.
Stable isotope data from the East Kirkton succession are used to elucidate the extent of hot-spring influence in the palaeoenvironment by constraining conditions of deposition of the silica and the formation of sulphides.
Petrographically silica occurs as chert laminae thought to be primary, and as patchy chert considered as replacive. No evidence for biogenic silica was observed. For 20 silica samples δ18O was measured for structural oxygen and δD for bound water. δ18O(SMOW) varied between +21 and +27‰ with no sample groupings related to petrography. The range in δD(SMOW) was from −50 to −90‰ with lower values characterising replacive or altered silica; water contents of both petrographic groups were similar. A plot of δ18O versus δD for the laminated primary silica defines a grouping about the line defined by Scottish agates (Fallick et al. 1985). This suggests for the unaltered silica a formation temperature of about 60°C and a fluid containing a strong component of meteoric water. The data imply a Lower Carboniferous meteoric water δ18O composition of −3‰ and δD of −15‰, consistent with the known palaeolatitude.
The only sulphide observed was pyrite; 34 samples were selected from a wide variety of lithological and textural occurrences. δ34S(CDT) ranges widely and continuously between +8 and −34‰ with no strong mode. The sulphur appears to be derived from several sources, and pyrite formation from a variety of conditions as indicated by such wide ranging data, but for the samples with the lowest δ34S the involvement of bacteria in sulphate reduction is inferred.
Magnetic and resistivity geophysical surveys conducted across the only known exposure of the East Kirkton Limestone have produced new information upon its extent. This is important to determine because of its unique faunal assemblage and possible hot spring deposition, suggesting a potential for precious metal mineralisation. Magnetic anomalies are attributed to basalts within the Bathgate Hills Volcanic Formation. Modelling of the magnetic data demonstrates a general dip to the west of about 25°, and the presence of significant local faulting. Modelling of vertical electrical sounding data shows the East Kirkton sequence (the limestone and associated beds) to be a low resistivity layer within the more highly resistive volcanic sequence. The East Kirkton sequence is seen to deepen to the west, and also to the north probably by faulting. Therefore the present exposure is the only near surface occurrence of the East Kirkton Limestone locally, but within the area of the survey no lateral limits to the formation are observed.
The puzzles regarding the magnitude of the free electron mobility in hydrogenated amorphous silicon are examined. It is suggested that highlevel double injection produces a metastable increase in the carrier mobility by neutralizing positively and negatively charged defect states thereby eliminating long-range potential fluctuations. Since these defect states cannot be neutralized under low-level or single injection, they both contribute to the modulation of the conduction band and increase the freecarrier scattering. If the latter is the predominant scattering mechanism, the neutralization of charged defects directly leads to a mobility increase under double-injection conditions. We discuss the various implications of this model, and present recent experimental results in agreement with these ideas.
We have examined spectrally resolved photoconductivity and photoluminescence from InAs/Ga1–xInxSb strained-layer superlattices, which have been proposed as infrared detectors in the 8-14 μm region. Our measurements indicate that the energy gaps of the strained–layer superlattices are substantially smaller than those of InAs/GaSb superlattices with similar layer thicknesses, in agreement with previous theoretical predictions. Measurements on InAs/Ga1–xInxSb superlattices with x=0 and 0.25 and layer thicknesses of 25 – 45 A indicate superlattice band gaps of 3 – 15 μm, in excellent agreement with gaps calculated by a two band k · p model. Our results demonstrate that far-infrared energy gaps are compatible with the thin layers necessary for strong optical absorption in type-IT superlattices, and suggest that InAs/Ga1–xInxSb superlattices are promising candidates for far-infrared detection.
We have analyzed photoluminescence spectra from CdxZnl−xTe /ZnTe and ZnSexTel−x/ZnTe strained layer superlattices grown by MBE, and obtained the band offsets by fitting to theory. We find that the valence band offset of the CdTe/ZnTe system is quite small (-50± 160 meV). In CdxZnl−xTe /ZnTe superlattices, the electrons and heavy holes are confined in the CdxZn1−xTe layers (type I), while the light holes are confined in the ZnTe layers (type II). On the other hand, the photoluminescence data from the ZnSexTe1−x /ZnTe superlattices suggest that the band alignment is type II, with a large valence band offset (−907 ± 120 meV). We also investigated the band bowing in the ZnSexTel−x alloys by optical spectroscopy, and found that there is only a small component of bowing in the valence band, while most of the bowing occurs in the conduction band. Based on our results for band alignments, we evaluate the prospects for minority carrier injection in wide bandgap heterostructures based on ZnSe, ZnTe, and CdTe.
A number of new amorphous silicon alloy microelectronic devices, including LCD active matrix displays, linear image sensors, and thin film multilayer computer memories, have been developed in our company. These applications rely heavily on the quality of the intrinsic semiconductor as well as its ability to withstand the many processing steps used in a modern photolithographic process. In this paper, we present electrical data on amorphous silicon alloy p-i-n diodes after such a process. These devices have an active area of 20μm × 20μm defined using standard photolithographic techniques and etched using a dry etch process. These diodes are characterized by ideality factors (n) of 1.4 and extrapolated reverse saturation current densities of 1013A/cm2h. The diodes exhibit nearly 10 orders of magnitude rectification at ± 3V and the reverse bias current density remains below 10-8 A/cm2 for reverse bias voltages of -15V. In pulsed forward bias, these diodes can be operated at current densities greater than 300A/cm2. Thin film amorphous silicon diodes moreover have the advantage that varying the thickness of the intrinsic layer allows the optimization of parameters such as the capacitance per unit area, the reverse bias current density and the forward bias conductance per unit area. We find that these devices are fully compatible with state of the art VLSI processing techniques and are suitable for applications in integrated circuit structures, for example rectification devices in microelectronic arrays and isolation devices in display matrices.
Thin film semiconductor devices have been investigated over the past twenty years for application in large area flat panel displays. The development of thin film transistors and diodes based on amorphous silicon (a-Si) alloy materials has made the application of these devices, to display technologies, very attractive. More recently, manufacturing techniques to produce high quality large area films of amorphous silicon alloys have been demonstrated for photovoltaic applications.
Most of the current research and development effort on active matrix liquid crystal displays (LCDs) has concentrated on a-Si alloy TFTs. The success of TFT based displays for large area flat panel displays has been limited so far, mainly due to the difficulty of obtaining a high quality gate dielectric by plasma deposition and due to the presence of crossing conductors on the same substrate, both increasing the probability of defects in the display. When a two terminal sandwich device is used, on the other hand, no gate dielectric is required, hence, a higher yield can be expected. Metal-insulator-metal and hydrogenated amorphous silicon alloy devices have been proposed for incorporation in LCDs. Performance requirements for a useful active matrix switching element and a comparison among the different a-Si alloy thin film devices used for this purpose will be reviewed.
We have grown a number of InAs and GaSb bulk layers on GaAs substrates and studied the properties of the semiconductor films as a function of the various growth parameters. Preliminary results from GaSb growth are presented in addition to an extensive study of InAs growth. The films were characterized during growth by RHEED. RHEED-oscillations were observed during both InAs and GaSb growths. Hall effect measurements yielded peak electron mobilities for InAs of 18,900 cm2/Vs at 300 K and 35,000 cm2/Vs at 77 K. For GaSb the as grown layers were found to be p-type with a carrier concentration of 9x1015cm-3 and a hole mobility of 910 cm2 /Vs at 300 K.
Little has been published about Te-rich ZnSexTel−x grown at low temperatures, in spite of some successes in the fabrication of wide band gap light emitting devices from ZnSeTe alloys grown at higher temperatures. We present x-ray diffraction and photoluminescence (PL) spectra for ZnSeTe epilayers and ZnSeTe/ZnTe superlattices grown by molecular beam epitaxy (MBE). These we compare with measurements on ZnTe, ZnSe and CdZnTe epilayers and on CdZnTe/ZnTe superlattices grown under similar conditions and also with data published for ZnSeTe alloys grown at high temperatures. Equilibrium phase diagrams for the ZnSeTe alloy system suggest a large miscibility gap at MBE growth temperatures; this may account for some unusual features in the (PL) spectra and for large line widths in the x-ray data. In spite of these possible miscibility problems, we find that ZnSeTe alloys luminesce brightly.
We report the development of a very high speed high resolution contact line imager using amorphous silicon alloy PIN diodes both as photosensing elements and as isolation diodes in the multiplexing scheme. High speed is achieved by reading the integrated photocurrent in 8μsec and using current integration times less than Imsec. For 200 dots/inch, the scan speed at an illumination of 5×10−4W/cm2 is over 1000 lines/sec. This allows the reading of an A4 (8½″×11″) page in less than 2.0 sec. At this light level, the signal to noise ratio is greater than 40dB. The photosensor array can be used in the true direct contact mode and the multiplexed addressing scheme gives a substantial reduction in the number of peripheral IC chips necessary for operation.
Single crystal NiSi2 films of type A and type B orientations with thicknesses ranging from 70–600Å have been grown on (111), n-type Si substrates. TEM and channeling measurements indicate that these films are of excellent epitaxial quality with uniform orientations over the entire range of observation. HRTEM studies show regular and atomically abrupt interfaces for both NiSi2 orientations with occasional localized planar defects. I-V and photoresponse measurements of the Schottky barrier heights(SBH) of the type A films yield consistent values of 0.62±.01eV. However, for type B films I-V measurements give a SBH of 0.69±.01eV while the photoresponse results give 0.77±.05eV. This discrepancy can be explained quantitatively by a phenomenological model in which a small percentage of low barrier height regions is incorporated into the type B films.
Electron tunneling spectroscopy experiments have been performed on single-crystal epitaxial silicide films grown on (111)-oriented (off 4 °) Si:As. 250 Å-thick films of CoSi2, and type-A and -B NiSi2 on degenerate substrates (Nd = 2 × 1019 cm−3) have been studied. All spectra show forward bias peaks at energies corresponding to k-conserving bulk Si phonons while in reverse bias only the Si TA phonon is observed for NiSi2 /Si structures. Plots of dV/dI vs. V for CoSi2 /Si structures yield maxima at a forward bias of 39meV, indicating an enhancement in n-type dopant concentration within ˜ 100 Å or more of the silicide-silicon interface.
The implications for recent reports of large valence band offsets the HgTe-CdTe heterojunction are examined. The variation of the band gap and effective mass for transport normal to the layers in the superlattice is examined in detail.