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We have observed fractional quantization of very few electrons confined in a semiconductor quantum dot using capacitance spectroscopy. The number of electrons per dot varies from 0 to about 40 as a function of bias on the quantum capacitors. The capacitance spectra have clear minima at gate voltages and magnetic fields, where the filling factors are 1/3 and 2/3. These measurements may allow direct comparison with few‐particle calculations.

We have made the first magnetotransport measurements of two‐dimensional holes confined to GaSb in modulation‐doped AlSb/GaSb heterostructures. The Shubnikov–de Haas oscillations in GaSb‐AlSb heterostructures reflect the influence of strain as well as the symmetry of the confinement potential on the hole levels. We have also observed the quantized Hall effect in asymmetric single quantum wells.

13 samples of Littorina saxatilis were collected from a Maine shore on an approximately monthly basis and analysed for soluble uric acid concentration. This concentration varied significantly, with summer concentrations as much as 6 times higher than winter concentrations. While it may be that the accumulation of uric acid in summer is related to desiccation, we suggest that it is more likely to be a result of increased protein catabolism.

Eighteen patients underwent stenting for symptomatic basilar artery stenosis. There were three major periprocedural complications (16.7%) without fatality. At a mean 26.7 ± 12.1-month follow-up, 15 patients (83.3%) had an excellent long-term outcome. Only one patient (5.6%) had moderate disability from recurrent stroke, and two patients died of medical illness at 30 and 36 months after stenting. In this uncontrolled study, stenting appeared to be effective in reducing stroke risk and death and worthy of further scrupulous trial.

The complexity of state-of-the-art silicon technology places great demands on the performance capability of each of the components of the circuit, from cell isolation to wire-bond pad. High on the list of critical performers is the interconnect wiring, which does not benefit from miniaturization as do devices. In fact, wiring performance worsens with ground rule reduction and die size increases. We summarize state-of-the-art on-chip wiring process technology as it pertains to microprocessor performance, suggest future trends for microprocessor performance, and indicate both technology and design solutions for the wiring bottlenecks created by today’s most demanding processor performance requirements. In addition, we address the feasibility of novel future wiring technologies for solving issues which plague conventional VLSI designs.

PURPOSE: To gain a preliminary understanding of the role of thrombolytic therapy for the thrombosed dural sinus, we retrospectively reviewed our initial experience. METHODS: Seven patients, ages 25 to 71, who presented with symptomatic dural sinus thrombosis and who failed a trial of medical therapy were treated with direct infusion of urokinase into the thrombosed sinus. Patients received urokinase doses ranging from 20,000 to 150,000 U/h with a mean infusion time of 163 hours (range 88 to 244 hours). RESULTS: Patency of the affected dural sinus was achieved with antegrade flow in all patients. Six patients either improved neurologically over their prethrombolysis state or were healthy after thrombolysis; one of them required angioplasty. The other patient improved after surgical repair of a residual dural arteriovenous fistula. The only complications were an infected femoral access site which resolved after treatment with antibiotics and hematuria which cleared after discontinuation of anticoagulation. CONCLUSIONS: Thrombolysis of the thrombosed dural sinus shows promise as a safe and efficacious treatment. The results of this study should provide the impetus for further research.

We have investigated magneto-transport properties of differently strained Si/ Si1−xGex resonant tunneling devices. The built-in strain was either put in the Si layers, by means of a thick., relaxed Si1−xGex buffer layer, or in the Si1−xGex layers, in which case all Si1−xGex layers were grown below the critical thickness, and a Si1−xGex spacer layer with graded Ge content was used. Magnetic fields parallel to the interface have been employed to probe the in-plane dispersion in the quantum well. This is used to study the effect of band-mixing in the two strain configurations. A field perpendicular to the interface resolves some Landau level splitting. Most strikingly, however, is the similarity in the spectra with the case when the magnetic field is applied parallel to the interfaces. This indicates broadening of the levels, possibly due to scattering, and the importance of 3-dimensional band structure effects.

Comparison of amino acid sequence data suggested that there may be a functional relationship between the staphylococcal epidermolytic toxins and V8 proteinase. The hypothesis was tested by treating epidermolytic toxin with di-isopropyl phosphorofluoridate, which bound specifically at serine-195, the homologue of the active-site serine residue of V8 proteinase.

Industry is the largest consumer for engineering and science doctorates, and doctorate-level training is thus a main link between the U.S. economy and education. Recent pressures on federal research and development funding, and the widening gap between the needs of industry and the expertise of academia, pose several challenges for the nature of graduate training. Fellowships, off-campus research, and opportunities for teaching should be emphasized in graduate schools, versus research assistant support.

The resonances of a resonant tunneling structure are probed by a magnetic field applied parallel to the interfaces, which enables us to investigate the local band structure in k space. By rotating the magnetic field in the plane of the interfaces the energy surface at constant k∥ is investigated. Using this technique differently strained Si/Si1−xGex quantum wells were studied, where with a large anisotropy of the energy levels was seen, with the symmetry axes of light holes and heavy holes being rotated 45° with respect to each other. In the case of resonant tunneling diodes with relaxed Si1−xGex quantum wells grown on thick, relaxed Si1−xGex buffer layers, the anisotropy is smaller, and without complete symmetry between different 90° in‐plane directions, which may be due to anisotropic strain relaxation in the Si1−xGex buffer layers.

We have studied the effect of strain and strain relaxation on the band structure of Si1−xGex quantum wells. Two differently strained, molecular‐beam epitaxy grown Si/Si1−xGex hole resonant tunneling structures were studied: one fully pseudomorphic structure, with the strain in the Si1−xGex well, and the other grown on a thick relaxed Si1−xGex buffer, with the strain in the Si barriers. For the latter structure transmission electron microscopy revealed a large threading dislocation density emanating from the buffer. Using angle‐resolved magnetotunneling spectroscopy we found an anisotropy in the hole states in different in‐plane 90° directions, that was not present in fully pseudomorphically grown structures. We suggest that this is due to anisotropic strain relaxation in the buffer layer.

This paper demonstrates a novel method for fabricating two‐dimensional lateral surface superlattices. The technique involves etching a grid into a GaAs/GaAlAs modulation‐doped heterostructure using a mask consisting of an array of 50‐nm diam Ni/Au dots with a 100–150 nm period. Bias applied to a Schottky gate deposited over the structured surface varies the coupling strength between dots. The devices can be tuned to operate in the superlattice (weak and strong coupling) or the quantum dot (no coupling) regimes. Low‐temperature characterization of the superlattices fabricated specifically for transport and capacitance measurements reveal novel magnetic field effects.

Single crystal silicon has been implanted with nitrogen and phosphorus ions at MeV energies to fluences between 1016 and 1.6 × 1018 ions/cm2. Infrared transmission and reflection spectra in the range of 1.25 to 40 μm were measured for as-implanted samples and after various annealing treatments. Interference fringes were observed in the IR spectra which are produced by the interference of light which has been multiply reflected between the front surface and the buried layers. By detailed theoretical analyses of the interference fringe structure, we obtained refractive index profiles, which, under suitable interpretation, provide accurate measurements and several quantities of interest. These quantities are the range and straggling of the implanted ions, the depth of disordered layers, and the width of the order-disorder transition. Mechanisms for the refractive index changes which have been identified include amorphization of the implanted silicon, bulk compositional change in the buried layer, lo...

Single particle relaxation time and the scattering time of the 2DEG in modulation doped GaAs/AlGaAs heterostructure are measured by Ladau respectively, for samples with spacer layer thickness 1.5–500 nm. The results are compared with the recent calculations of Das Sarma and Stern and excellent agreement is obtained. When the excited subband is occupied under persistent photoconductive (PPC) conditions, the relaxation time for the excited subband was found to be nearly three times longer than that for the ground subbands. The results are interpreted in terms of screened remote impurity scattering.

We have measured the two-terminal AC conductance of (AlGa)AsGaAs heterostructures and a silicon MOSFET up to 50 MHz. While the ungated heterostructure samples show no frequency dependence in the integer and no additional structure in the fractional quantum Hall regimes, the gated silicon MOSFET shows strong frequency dependence of the two-terminal AC conductance due to coupling of the signal from the 2DEG to the gate. We have also measured the capacitance of the silicon MOSFET under the same circumstances, and thereby confirm the role of the gate in coupling the high frequency signal.

We have made the first measurements of cyclotron resonance and the Shubnikov-de Haas effect in two-dimensional electronic system confined to AlAs. Cyclotron resonance data show that the effective mass for (100)-oriented samples (0.5m0) is larger than for (111)-oriented samples (0.41m0). This indicates that the X point ellipsoids with their long axes parallel to the interface are occupied. This may be due to compressive stress in the AlAs. From the temperature and magnetic field dependence of the Shubnikov-de Haas oscillations we have also determined the effective mass (m(111)∗ = 0.49m0; m(100)∗ = 0.60m0) and the effective g-factor (g∗ = 3.1−3.4). We find fairly good agreement between measured and calculated values.

We observe the magnetic-field-induced bifurcation of quantum levels into surface states and bulklike Landau States. The disruption of the electric field quantization by a magnetic field is most dramatic for electrons bound in two dimensions perpendicular to the magnetic field. The interplay between competing spatial and magnetic quantization mechanisms results in a pronounced and complex level splitting. The observed splitting of zero-dimensional energy levels depends critically on the size of the quantum dots, and can be explained with a calculated single-particle energy spectrum.

The treatment of renal and ureteral stones has undergone rapid and major changes over the past ten years. Extracorporeal Shockwave lithotripsy has become the most commonly used modality for the treatment of renal and upper ureteral stones. Lower ureteral stones are more commonly being approached by retrograde techniques. Percutaneous nephrolithotomy, medical therapy, and open surgical nephrolithotomy offer viable alternatives in given situations. Presented here is the current application of each of these techniques, both alone and in combination, for the treatment of urinary stones.

We have made magnetotransport measurements on two-dimensional electronic systems confined to AlAs by ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As. We have determined the effective mass (${m}_{111}$=0.49${m}_{0}$), the effective g factor (3.1), and the relaxation time. Even though the lattice constants of GaAs and AlAs are nearly equal, the stress arising from this small mismatch strongly influences the electronic properties of AlAs. For [111]-oriented samples the valley degeneracy is one, and there is an anomalous phase shift in the Shubnikov--de Haas oscillations.

Die Photolyse des Dithiocarbamatokomplexes (I) in Chloroform oder Chlorbenzol fuhrte zur Bildung der Verbindung (II).

We have studied pulsed ruby laser and furnace annealing of high‐dose (D>1017 N/cm2) 50‐keV nitrogen‐implanted silicon. Using Rutherford backscattering and channeling, transmission electron microscopy, and infrared transmission spectroscopy, we have compared liquid and solid phase regrowth, diffusion, impurity segregation, and nitride formation. As has been previously reported, during furnace annealing at or above 1200 °C nitrogen redistributes and forms a polycrystalline silicon nitride (Si3N4) layer. In contrast, pulsed laser melting produces a buried amorphous layer containing silicon and nitrogen with only very small amounts of polycrystalline silicon nitride below a layer of polycrystalline silicon.

We present new data concerning the problem of two-subband transport in a two-dimensional electron gas. We find that the ratio of the mobilities of electrons in the two subbands depends on the details of the confinement potential, while the ratio of the relaxation times determined from the Shubnikov-de Haas effect does not. In all samples studied the relaxation time determined from the amplitude of quantum oscillations in the magnetoresistance is longer for electrons in the upper subband. In addition, we see evidence for the repulsion of quantum levels and the inhibition of spin-flip transitions between quantum levels.

We have studied the two-dimensional properties of high-mobility electron-hole systems in InAs quantum wells bounded by Ga 1− x Al x Sb. By changing the alloy composition x , we are able to vary the system from quasi-semimetallic (with unequal electron and hole carrier concentrations) to semiconducting (with only electrons). Furthermore, we have observed a magnetic-field-induced semimetal-to-semi-conductor transition which manifests itself in the magnetotransport properties of samples with both carriers. This transition can be understood by considering the continuity of the Fermi energy across the InAs/Ga 1− x Al x Sb interface and the interdependence of the electron and hole densities.

Single‐crystal silicon has been implanted with nitrogen ions at MeV energies, to fluences between 0.25×1018 and 1.65×1018 ions/cm2 at a substrate temperature of 700 °C. Infrared transmission and reflection spectra in the range of 1.25–40 μm were measured and interference fringes were observed which are produced by the interference of light which has been multiply reflected between the front surface and the buried layers. By detailed theoretical analyses of the interference fringes we obtain refractive‐index profiles, which, under suitable interpretation, provide accurate measurements of the range and straggling of the implanted ions. Rutherford backscattering measurements on the same samples confirm this interpretation. Between the energies of 0.67 and 3.17 MeV, the measured values of the projected range agree with theory after adjusting the electronic stopping power, but the straggling measurements are lower by ∼30%. It is demonstrated that the asymmetry of the range distribution can be measured with thi...

We have measured the thermodynamic properties of dispersionless electronic systems. We observe structure in the capacitance of quantum dots reflecting the discrete energy levels of electrons confined in all three spatial dimensions. The spacings of the observed structure and the systematic variation with the degree of confinement are consistent with quantum-size effects.

Measurements of the magnetocapacitance of a two-dimensional electron gas in high mobility GaAs(Ga, Al)As heterostructure confirm, for the first time, the relationship between the density of states and the capacitance of a two-dimensional electron gas. We present the first magnetocapacitance measurements in the fractionally quantized Hall regime.

We have studied the transition from isolated to coupled quantum dots in a lateral surface‐superlattice structure in the presence of a perpendicular magnetic field. The coupling between the dots can be tuned by changing the bias of the grid gate. Our magnetocapacitance measurements reveal three distinct regimes: isolated quantum dots where collective effects are not observed, a tight‐binding regime where the measurement results are sensitive to the rationality of flux quanta per unit cell, and a superlattice regime where commensurability effects between the magnetic orbits and the superlattice periodicity are observed.

The records of 37 patients who had undergone splenoportography, including one group of 12 who were studied before 1976 and a second group of 25 who were studied after 1977, were reviewed. The primary difference was that in the second group, the tract in the spleen was occluded with absorbable gelatin sponge (Gelfoam) plugs as the needle was withdrawn. In addition, there were minor changes in technique, such as changes in the needle puncture angle and entry site. When the new technique was used, there was a significant decrease in the complications traditionally associated with splenoportography. This procedure is safe and deserves to be considered the procedure of choice in patients in whom precise anatomic information is needed preoperatively that cannot be obtained with noninvasive procedures such as ultrasound or magnetic resonance imaging.

Post‐anneals of short duration at high temperature are shown to improve significantly the quality of CaF2 films on Si (100). An anneal at 1100 °C for 20 s in an Ar ambient reduced χmin, the ratio of backscattered 1.8‐MeV 4He+ ions in the aligned to random direction, from 0.26 for an as‐grown CaF2 film to 0.03 following the post‐anneal. This is the best χmin yet reported for the CaF2:Si (100) system. The post‐anneal films also show improved chemical, mechanical, and electrical properties.

Electron cyclotron resonance and radio frequency reactive ion etching have been used to fabricate narrow n+‐GaAs wires employing CCl2F2/He as the etch gas. A comparison of the induced sidewall damage is made using room‐temperature conductivity measurements of the etched structures and the effect of overetching is investigated. In addition, preliminary analysis of low‐temperature transport reveals that the amplitude of universal conductance fluctuations is extremely sensitive to sidewall damage.

Fabrication of metal‐epitaxial insulator‐semiconductor field‐effect transistors by molecular beam epitaxial growth of CaF2 on Si is reported for the first time. These devices have a room‐temperature electron mobility of 300 cm2/Vs and a threshold voltage of 0.5 V. The breakdown voltage of the films ranges from ≳105 to ≳106 V/cm in different regions of the film. These devices will be important for the characterization and improvement of the interface transport properties of the CaF2/Si system.

The rates of self-exchange for several systems of the class MCp/sub 2/X/sup +//Cp/sub 2/, where M is Ru or Os and X is Cl, Br, or I, have been measured by the NMR line-broadening method. For each metal, the rates increase along the halogen series as given above and are more rapid for M = Ru than for the osmium analogues. In consideration of these data, the possibility is raised that these 2e self-exchange reactions and those of other metal ions take place by 1e steps.

We have made magnetotransport measurements on two-dimensional electronic systems with two subbands occupied. We have determined the mobility for electrons in the lowest and first excited subband and find that the electrons in the upper subband have a higher mobility. This is consistent with our recent determination of the single-particle relaxation time but contrary to previous results and assumptions concerning two-subband transport.

We describe how the unique capabilities of molecular beam epitaxy together with the electron-beam lithography and reactive-ion etching can be utilized to realize novel quasi-one- and zero-dimensional electron systems. We also present the results of capacitive and tunneling studies on these quantum systems.

We have devised and demonstrated a novel technique for fabricating structures with nanometer scale features in semiconductor heterostructures. The technique is based on definition of nanometer scale patterns by submicron trenches in a GaAs‐AlGaAs heterostructure. The depletion of free carriers below the trenches gives rise to very strong electrostatic confinement. This technique avoids the complications associated with the use of negative resist materials and lift‐off techniques while minimizing the time required to expose densely packed patterns. Aharonov–Bohm rings fabricated using this technique exhibit interference oscillation larger than any reported previously.

Rats were given 6 days of training (180 trials) to make a two-way (shuttle) avoidance response. "Poor performers" making less than 50% avoidances in the 6th block of 30 tials were given drug treatments on the next 2 days. Both morphine sulfate (15 mg/kg) and d-amphetamine sulfate (1 mg/kg) increased the avoidance level by 70-100%. Prior treatment with alpha-methyltyrosine (50 mg/kg) prevented the effects of both drugs. Nalorphine hydrochloride (5 mg/kg) also blocked the effect of morphine. The action of alpha-methyltyrosine to block enhancement of avoidance is taken to indicate that this effect of morphine is attributable to a catecholamine-dependent excitatory component of its activity profile.

We show that post anneals of short duration at high temperature can markedly improve the quality of CaF2 films grown by molecular beam epitaxy (MBE) on Si (100). Anneals at 1100°C for 20 sec in an Ar ambient improved χmin, the ratio of backscattered 1.8 MeV He4 ions in the aligned to random direction, from as-grown values of .07 to .26, to post post-anneal values of .03 to .045. This is the best χmin yet reported for the CaF2:Si system. The post-annealed films also show improved resistance to chemical etching and mechanical stress, and increased dielectric breakdown voltages.

We present a direct measurement of the density of states of a two-dimensional electron gas in a quantizing magnetic field. By measuring the magnetocapacitance of modulation-doped GaAs-(AlGa) As heterostructures at low frequencies, we have observed quantum oscillations resulting from changes in the density of states alone.

Rapid thermal annealing (RTA) has been shown to be a useful technique for improving the epitaxial quality of CaF2 films grown on Si(100) by molecular beam epitaxy. We have modified the annealing procedure to prevent crack formation, while still maintaining high film quality. Our work also shows RTA to be useful for improving the crystalline quality, chemical stability, and electrical characteristics of CaF2 films grown on Si(111). After RTA, the crystallinity of CaF2 films on Si(111), as measured by electron channeling, is indistinguishable from bulk single crystal CaF2, and the interface state density is reduced by nearly two orders of magnitude from that found in as-grown films.

Die Photolyse des Dithiocarbamatokomplexes (I) in Chloroform oder Chlorbenzol fuhrte zur Bildung der Verbindung (II).

The applicability of readability to the development of pharmacy educational materials is reviewed. The importance of reading skills must be recognized in all areas of education, including pharmacy patient education. If people are to perform certain tasks, they must understand the instructions for those tasks. To be understandable, the instructions must be written on the reading level of the people who will be following the instructions. Readability has been defined as those characteristics of reading materials, involving certain mental processes, that make for ease or difficulty of comprehension of the reading material. It is the task of the reader to use as few or as many of these mental processes as necessary to grasp the intended meaning of the material. It has been estimated that the average reading level of the American public is approximately 7th to 8th grade. However, many adults do not have sufficient reading skills to comprehend fully material written on these levels. Therefore, pharmacy educational material should be written on the reading level of the patient population it serves. Several readability formulas have been developed to evaluate the various characteristics of reading material that lead to reading comprehension. Among the ones recommended for use with pharmacy educational materials are the Fry Readability Graph and the Gunning Fog Index.