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This article proposes a novel capacitor-voltage balancing strategy for the double-Y modular multilevel converter static synchronous compensator operated under unbalanced current conditions of the system. The proposed method, based on zero-sequence voltage injection, manipulates the current distribution between the converter arms to minimize the converter ratings. The proposed balancing strategy is compared with the classical approach, based on controlling the circulating dc currents. For the same unbalanced conditions, the proposed strategy leads to lower energy rating for the converter as compared with the classical one, whereas the semiconductor ratings remain the same in both strategies. Theoretical findings are verified through experimental results.

The share of renewables in the power system is increasing rapidly. Large offshore wind power plants (OWPPs) are developed at a high pace and conventional fossil fuel-based plants are decommissioned. If the OWPP gets islanded due to any contingency or in the event of a blackout, the whole OWPP will be shutdown. This paper proposes a STATCOM with a battery storage that is located at the point of common connection to an OWPP to enable OWPP energization from a fully discharged state to operate in islanded mode. The STATCOM functionality provides fast and dynamic reactive power management and the battery unit provides active power balancing capability to regulate the frequency in the island. The concept is demonstrated through time-domain simulations on an OWPP model in PSCAD. The results confirm the technical feasibility of the system.

The aim of this paper is to investigate the impact of steady-state deviations in the grid-frequency on the performance of grid-forming converter control strategies. In particular, the virtual synchronous machine (VSM) control structure has been the focus of study in this paper. Two alternative solutions to address the issue with the conventional VSM structure are suggested, and their impact on the active power response and the power dissipation properties of the converter are compared. For the latter, the ac-side input admittance of the grid-connected converter is derived for the different control structures under consideration. Finally, the dynamic performance of the different control structures is verified through the time-domain simulations.

A controller for a hybrid converter for STATCOM applications, based on a cascaded H-bridge star in series with a generic converter connected at the star point, is proposed. The controller utilizes the generic converter in an optimized way to maximize the operating range of the converter, with focus on unbalanced operating conditions. So for each operating condition, the generic converter reference voltage minimizes the voltage rating of the star part. Theoretical investigations of the hybrid converter using the proposed control approach show that the hybrid converter allows to effectively extend the operating range of the converter under unbalanced conditions of the system, given that the generic converter is large enough to circulate the needed active power between the converter phase legs. This indicates that, depending on the requirements from the operator in terms of negative-sequence injection capability, the hybrid converter can be a valuable solution to overcome the limitations of the CHB star.

This paper proposes a modular multilevel converter (MMC) topology, designed particularly for load balancing in 50 Hz railway applications. The asymmetrical character of the traction load requires higher device rating for a Double-star or Delta-connected MMC compared to a symmetrical static compensator. This is due to the symmetrizing components to rebalance the capacitor voltages in the submodules. In this paper a reduced chain-link MMC topology, consisting of a two phase-leg converter, is proposed in order to avoid overrating the semiconductors in the main current path. In addition, the main circuit is equipped with dc-dc dual half-bridge (DHB) converters that connect the submodule capacitors of the two legs. The DHBs are operating as “Power Channels,” enabling energy exchange to restore the power imbalance among the capacitors. Simulation results show that the proposed converter is capable of achieving load balancing under any operating conditions, while the balance of the capacitor voltage is ensured.

This paper evaluates three alternative topologies for a static compensator (StatCom), suitable to eliminate the negative-sequence currents in a railway system. The compensator is placed in a transformer substation, which feeds two separate sections of the catenary. The major requirements of this converter is to: (i) symmetrize the railway load as seen from the high-voltage side, (ii) control the catenary voltage to a defined level, and (iii) compensate for the harmonics generated by the rolling stock. The topologies investigated here are: (a) a 2-level converter with a common dc-bus capacitor, (b) a delta-connected modular multilevel converter (MMC) based on full-bridge submodules, and (c) a double-star MMC based on half-bridge submodules. The evaluation is based on the minimum device-rating requirements of each converter that fulfill the application requirements in the steady-state. Simulation results are provided to support the conclusions of this evaluation.

This paper investigates issues related to practical implementation of the one-quarter of cycle-based estimation method [here called delayed signal cancellation (DSC)] for online detection of positive and negative sequence components of three-phase quantities. The detection error due to non-ideal sampling frequency is calculated. Furthermore, the effect of the DSC method on estimation when harmonic components are present in the input signal is analyzed. It is shown how harmonics transfer through the DSC and how a non-ideal sampling frequency affects the estimation of the harmonics. Experimental verification of the analytical results is presented.

In this paper, a novel control strategy for subsynchronous resonance (SSR) mitigation using a static synchronous series compensator (SSSC) will be presented. The SSSC is constituted by three single-phase voltage source converters. SSR mitigation is obtained by increasing the network damping only at those frequencies that are critical for the turbine-generator shaft. This is achieved by controlling the subsynchronous component of the grid current to zero. Using the IEEE First benchmark model, the effectiveness of the proposed control algorithm when mitigating SSR due to torsional interaction and torque amplification effect will be shown.

The full potential of biologically optimized radiation therapy can only be maximized with the prediction of individual patient radiosensitivity prior to treatment. Unfortunately, the available biological parameters, derived from clinical trials, reflect an average radiosensitivity of the examined populations. In the present study, a breast cancer patient of stage I-II with positive lymph nodes was chosen in order to analyse the effect of the variation of individual radiosensitivity on the optimal dose distribution. Thus, deviations from the average biological parameters, describing tumour, heart and lung response, were introduced covering the range of patient radiosensitivity reported in the literature. Two treatment configurations of three and seven biologically optimized intensity-modulated beams were employed. The different dose distributions were analysed using biological and physical parameters such as the complication-free tumour control probability (P(+)), the biologically effective uniform dose (D), dose volume histograms, mean doses, standard deviations, maximum and minimum doses. In the three-beam plan, the difference in P(+) between the optimal dose distribution (when the individual patient radiosensitivity is known) and the reference dose distribution, which is optimal for the average patient biology, ranges up to 13.9% when varying the radiosensitivity of the target volume, up to 0.9% when varying the radiosensitivity of the heart and up to 1.3% when varying the radiosensitivity of the lung. Similarly, in the seven-beam plan, the differences in P(+) are up to 13.1% for the target, up to 1.6% for the heart and up to 0.9% for the left lung. When the radiosensitivity of the most important tissues in breast cancer radiation therapy was simultaneously changed, the maximum gain in outcome was as high as 7.7%. The impact of the dose-response uncertainties on the treatment outcome was clinically insignificant for the majority of the simulated patients. However, the jump from generalized to individualized radiation therapy may significantly increase the therapeutic window for patients with extreme radio sensitivity or radioresistance, provided that these are identified. Even for radiosensitive patients a simple treatment technique is sufficient to maximize the outcome, since no significant benefits were obtained with a more complex technique using seven intensity-modulated beams portals.

In this paper, a novel control strategy for subsynchronous resonance (SSR) mitigation using a static synchronous series compensator will be presented. SSR mitigation is obtained by increasing the network damping only at those frequencies that are critical for the turbine-generator shaft. This is achieved by controlling the subsynchronous component of the grid current to zero. Using the IEEE first benchmark model, the effectiveness of the proposed control algorithm when mitigating SSR due to torsional interaction and torque amplification effect will be shown.

In this paper, the problem of online estimation of subsynchronous frequency components in the measured grid voltage is treated. Two estimation methods, one based on the use of lowpass filters and a recursive least square algorithm, are investigated and compared. In particular, due to its higher degree of freedom in the design, the lowpass filters-based estimation method is found to be the most appropriate and accordingly further analyzed. The method is improved to cope with inaccurate knowledge of the subsynchronous frequency. The simulation results prove the effectiveness of the investigated method both for the ideal and the disturbed case.

In this paper, the use of a method for online detection of positive- and negative-sequence components of three-phase quantities, named the delayed signal cancellation (DSC) method, is investigated. Problems that arise in practical implementation of the DSC method in computer-controlled systems are investigated. Expressions of the detection error due to nonideal discretization are derived and calculations are verified experimentally. Two methods for reducing the detection error are presented and verified. It is also shown that the given expressions and proposed methods for reducing the detection errors can also be applied to the case of grid frequency variations

We summarize the inflight performance of JEM-X, the X-ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM-X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis. Reglero Velasco, Victor, Victor.Reglero@uv.es ; Martinez Nuñez, Silvia, Silvia.Martinez@uv.es

Energy storage will gain importance in the future power system due to increased amount of renewables. In this paper, a utility scale Battery Energy Storage System (BESS) for megawatt utilizing a high voltage and a high power Voltage Source Converter (VSC) is proposed to be able to inject/consume the required power and energy to the grid. The batteries are both series and parallel connected on the DC-side of the VSC. In order to obtain high reliability, high availability and safety of the BESS, this paper proposes and analyzes a distributed Solid-State DC Breaker protecting the BESS and its batteries.

Spectroscopic measurements were made of the population of the excited states in a low-voltage, low-temperature, open caesium plasma diode. Such a device is under certain conditions seen to run in a special mode that is essentially different from the ordinary plasma mode. This mode, which has been called the Rydberg current mode, exhibits many interesting features, such as a very strong electron emission from the cold to the hot electrode. The objective of the present study was to investigate and compare the plasma conditions of the two modes. The spectral line intensities and the excitation temperatures of the upper states were found to differ considerably although the current, the voltage and the electrode temperatures were comparable.

In this survey paper, applications of medium voltage direct current (MVDC) to distribution substations are discussed and compared to conventional ac for power conversion from transmission voltage levels to distribution voltage levels. Technical changes in the substation due to the dc equipment, efficiency of the substation, and protective measures are major aspects to consider in the MVDC concept development.

The inheritance of 23 protein polymorphisms was compared with the inheritance of a DNA restriction fragment length polymorphism (RFLP) of a strongly cross-hybridizing erb B-related sequence, epidermal growth factor receptor-like-1 (EGFRL1), in Xiphophorus clemenciae X X. milleri-derived backcross hybrids. Two polymorphic bands were noted in this cross with a v- erb B probe after Pst I digestion: a 10-kilobase (kb) band in X. clemenciae and a 9-kb band in X. milleri. Joint segregation analysis of the RFLPs and protein polymorphisms indicate that this erb B-related sequence can be assigned to Xiphophorus linkage group VI, which also comprises genes coding for glutamine synthetase ( GLNS ), nucleoside phosphorylase-2 ( NP2 ), and transferrin ( TF ). We have designated this RFLP as alleles at a locus called EGFRL1 because of very strong cross-hybridization with the v- erb B probe, known to be homologous to the mammalian EGFR gene. This mapping assignment is the first autosomal linkage of an oncogene sequence reported in fish, which provide a large number of genetically controlled experimental tumor models.

This paper deals with the analysis and simulation of the static series compensator (SSSC) for subsynchronous resonance (SSR) mitigation. The purpose of the paper is to derive and analyze a novel control strategy for SSSC dedicated for SSR mitigation. Objective of the proposed controller is to increase the network damping only at those frequencies that are critical for the turbine-generator shaft. By using frequency scanning analysis, the effectiveness of the proposed method for mitigation of SSR due to torsional interaction effect is presented and compared with the existing control strategy. Finally, simulation results show the performance of the proposed method in mitigating SSR due to torque amplification effect.

Aims Because of the highly conformal distributions that can be obtained with intensity-modulated radiotherapy (IMRT), any discrepancy between the intended and delivered distributions would probably affect the clinical outcome. Consequently, there is a need for a measure that would quantify those differences in terms of a change in the expected clinical outcome. Materials and methods To evaluate such a measure, cancer of the cervix was used, where the bladder and rectum are proximal and partially overlapping with the internal target volume. A solid phantom simulating the pelvic anatomy was fabricated and a treatment plan was developed to deliver the prescribed dose to the phantom. The phantom was then irradiated with films positioned in several transverse planes. The racetrack microtron at 50MV was used in the treatment planning and delivery processes. The dose distribution delivered was analysed based on the film measurements and compared against the treatment plan. The differences in the measurements were evaluated using both physical and biological criteria. Whereas the physical comparison of dose distributions can assess the geometric accuracy of delivery, it does not reflect the clinical effect of any measured dose discrepancies. Results It is shown how small inaccuracies in delivered dose can affect the treatment outcome in terms of complication-free tumour cure. Conclusions With highly conformal IMRT, the accuracy of the patient set-up and treatment delivery are critical for the success of the treatment. A method is proposed to evaluate the precision of the delivered plan based on changes in complication and control rates as they relate to uncertainties in dose delivery.

Power electronics converters connected in series with the grid can provide protection of sensitive processes against voltage dips. In this paper, an advanced cascade controller for series-connected voltage source converter (VSC), constituted by an outer voltage loop and an inner current loop, is presented. Positive and negative sequence components of voltage and current are controlled separately to achieve perfect compensation of unbalanced dips. Limitation of the VSC output voltage and compensation of the computational time delay are included in the current controller for both sequence components. Experimental results for the series-connected VSC with the proposed cascade controller under balanced and unbalanced voltage dips are presented.

The increasing use of voltage source converters (VSCs) in grid-connected applications at distribution levels requires control methods that achieve high performance not only during normal operating conditions of the grid, but also under voltage disturbances, like voltage dips. In this paper, three different current controllers for shunt-connected VSC are investigated. With a constant DC-link voltage, the three controllers are compared under balanced and unbalanced voltage dips. Simulation and experimental results are shown for all three controllers.

The production work concerning the Third Precise Levelling of Sweden is almost completed. The next necessary step concerns further quality control of the levelling data before the final adjustment can be done. The production line, from planning to computation, has been developed to minimise the influence of systematic errors as well as minimising the risk of gross errors. This paper describes the whole process of the production to present how we are trying to minimise the error budget by proper planning, well developed measuring technique and different types of checks of data in the field as well as in the office. The paper also describes the work planned to prepare our data for the final adjustment so that the remaining systematic errors can be detected and controlled.

High energy photon therapy beam from the 50 MV racetrack microtron has been evaluated using the Monte Carlo code MCNP4B. The spatial and energy distribution of photons, radial and depth dose distributions in the phantom are calculated for the stationary and scanned photon beams from different targets. The calculated dose distributions are compared to the experimental data using a silicon diode detector. Measured and calculated depth-dose distributions are in fairly good agreement, within 2-3% for the positions in the range 2-30 cm in the phantom, whereas the larger discrepancies up to 10% are observed in the dose build-up region. For the stationary beams the differences in the calculated and measured radial dose distributions axe about 2-10%.

As a result of availability studies, comparing a traditional substation configuration with conventional equipment and an innovative solution with disconnecting circuit breakers, the latter was found drastically better with regard to power flow. The use of disconnecting circuit breakers also leads to a reduction of the total number of HV apparatus in the substation with associated reduction of space requirements and costs.

Increases in cell proliferation are widely viewed as being of importance in carcinogenesis. We report that exposure of normal human lung fibroblasts to a low dose of alpha particles like those emitted by radon/radon progeny stimulates their proliferation in vitro, and this response also occurs when unirradiated cells are treated with supernatants from alpha-irradiated cells. We attribute the promitogenic response to superoxide dismutase- and catalase-inhibitable a particle-induced increases in the concentrations of transforming growth factor beta1 (TGF-beta1) in cell supernatants. TGF-beta1 at concentrations commensurate with those in the supernatants capably induces increases in intracellular reactive oxygen species (ROS) in unirradiated cells. Furthermore, the addition of supernatants from alpha-irradiated cells to unirradiated cells decreases cellular levels of TP53 and CDKN1A and increases CDC2 and proliferating cell nuclear antigen in the latter. Like the increased intracellular ROS bystander effect, this "decreased TP53/CDKN1A response" can be mimicked in otherwise untreated cells by the addition of low concentrations of TGF-beta1. Our results indicate that alpha particle-associated increases in cell growth correlate with intracellular increases in ROS along with decreases in TP53 and CDKN1A, and that these cellular responses are mechanistically coupled. As well, the proliferating cell nuclear antigen and CDC2 increases that occur along with the decreased TP53/CDKN1A bystander effect also would expectedly favor enhanced cell growth. Such processes may account for cell hyperplastic responses in the conducting airways of the lower respiratory track that occur after inhalation exposure to radon/ radon progeny, as well as, perhaps, other ROS-associated environmental stresses.

Not until the last decade has flexible intensity modulated three-dimensional dose delivery techniques with photon beams become a clinical reality, first in the form of heavy metal transmission blocks and other beam compensators, then in dynamic and segmented multileaf collimation, and most recently by scanning high-energy narrow electron and photon beams. The merits of various treatment unit and bremsstrahlung target designs for high-energy photon therapy are investigated theoretically for two clinically relevant target sites, a cervix and a larynx cancer both in late stages. With an optimized bremsstrahlung target it is possible to generate photon beams with a half-width of about 3 cm at a source to axis distance (SAD) of 100 cm and an initial electron energy of 50 MeV. By making a more compact treatment head and shortening the SAD, it is possible to reduce the half-width even further to about 2 cm at a SAD of 70 cm and still have sufficient clearance between the collimator head and the patient. One advantage of a reduced SAD is that the divergence of the beam for a given field size on the patient is increased, and thus the exit dose is lowered by as much as 1%/cm of the patient cross section. A second advantage of a reduced SAD is that the electron beam on the patient surface will be only about 8 mm wide and very suitable for precision spot beam scanning. It may also be possible to reduce the beamwidth further by increasing the electron energy up to about 60 MeV to get a photon beam of around 15 mm half-width and an electron beam as narrow as 5 mm. The compact machine will be more efficient and easy to work with, due to the small gantry and the reduced isocentric height. For a given target volume and optimally selected static multileaf collimator, it is no surprise that the narrowest possible scanned elementary bremsstrahlung beam generates the best possible treatment outcome. In fact, by delivering a few static field segments with individually optimized scan patterns, it is possible to combine the advantage of being able to fine tune the fluence distribution by the scanning system with the steeper dose gradients that can be delivered by a few static multileaf collimator segments. It is demonstrated that in most cases a few collimator segments are sufficient and often a single segment per beam portal may suffice when narrow scanned photon beams are employed, and they can be delivered sequentially with a negligible time delay. A further advantage is the increase of therapeutically useful photons and improved patient protection, since the pencil beam is only scanned where the leaf collimator is open. Consequently, some of the problems associated with dynamic multileaf collimation such as the tongue and groove and edge leakage effects are significantly reduced. Fast scanning beam techniques combined with good treatment verification systems allow interesting future possibilities to counteract patient and internal organ motions in real time.

The majority of patients from 4 orthodontic clinics in the south west of Sweden who have had bonded retainers on upper or lower anterior teeth for a period of at least 5 years were examined. The total failure rate during 5 years of observation was 36 per cent, slightly higher in the maxilla than in the mandible. The retainer had become detached in 15 per cent of the teeth bonded. The failure rate decreased during the 5 year period of observation. Seven fractures were reported, all in the upper front teeth. The failure rate was reduced when the retainers were positioned incisally, when larger diameter wires were used and in the 12 cases where a groove had been cut into the enamel to accept the retainer. The findings suggest that a limited flexibility of the retainer may be an advantage. In about 20 per cent of the retained segments minor rotations and small areas of space opened between some of the teeth attached to the retainer. No new caries lesions were found on any of the teeth associated with the bonded retainers during the period of observation.

Fish gene mapping studies have identified several syntenic groups showing conservation over more than 400 million years of vertebrate evolution. In particular, Xiphophorus linkage group IV has been identified as a homolog of human chromosomes 15 and 19. During mammalian evolution, loci coding for glucosephosphate isomerase, peptidase D, muscle creatine kinase, and several DNA repair genes ( ERCC1, ERCC2 , and XRCC1 ) appear as a conserved syntenic group on human chromosome 19. When X. clemenciae and X. milleri Pst I endonuclease-digested genomic DNA was used in Southern analysis with a human ERCC2 DNA repair gene probe, a strongly cross-hybridizing restriction fragment length polymorphism was observed. Backcrosses to X. clemenciae from X. milleri × X. clemenciae F 1 hybrids allowed tests for linkage of the ERCC2 -like polymorphism to markers covering a large proportion of the genome. Statistically significant evidence for linkage was found only for ERCC2L1 and CKM (muscle creatine kinase), with a total of 41 parents and 2 recombinants (4.7% recombination, χ 2 = 35.37, P GPI and PEPD in linkage group IV was detected. The human chromosome 19 synteny of ERCC2 and CKM thus appears to be conserved in Xiphophorus , while other genes located nearby on human chromosome 19 are in a separate linkage group in this fish. If Xiphophorus gene arrangements prove to be primitive, human chromosome 19 may have arisen from chromosome fusion or translocation events at some point since divergence of mammals and fishes from a common ancestor.

Synchrotron self-absorption is a powerful heating mechanism for low energy particles emitting and absorbing synchrotron photons. They are driven towards a thermal distribution in a few cooling times. The inhibition of synchrotron cooling has important consequences for the overall spectrum of the emitted radiation.

Purpose: Due to the highly conformal distributions that can be obtained with intensity modulated radiation therapy(IMRT), any discrepancy between the intended and delivered distributions would likely affect the clinical outcome. Consequently, there is a need for a measure that would quantify those differences in terms of a change in the expected clinical outcome. Material and Methods: To evaluate such a measure, the case of a cervix cancer was used where the bladder and rectum, are proximal and partially overlapping with the internal target volume. A solid phantom simulating the pelvic anatomy was fabricated and a treatment plan was developed to deliver the prescribed dose to the phantom. The phantom was then irradiated with films positioned in several transverse planes. The racetrack microtron at 50MV was used in the treatment planning and delivery processes. The dose distribution delivered was analyzed based on the film measurements and compared against the treatment plan. The differences in the measurements were evaluated using both physical and biological criteria. Results: For the computerized treatment plan, the maximum value of P + was 84.1%, for a mean dose to the ITV of D = 93.3Gy, associated relative standard deviation σ D /D = 16.8% and biologically effective uniform dose,D ITV of 89.2 Gy. The delivereddose distribution from all the beams produced a P + value of 77.0% for D ITV = 93.2 Gy , σ D /D = 19.0% and D ITV of 83.5 Gy. Discussion and Conclusions: Whereas the physical comparison of dose distributions can assess the geometric accuracy of delivery, it does not reflect the clinical impact of any measured dose discrepancies. With highly conformal IMRT, the accuracy of the patient setup and treatmentdelivery, are critical for the success of the treatment. A method is proposed to evaluate the precision of the delivered plan based on changes in complication and control rates as they relate to uncertainties in dosedelivery.

Biological treatment optimization aim at improving radiation therapy by accounting for the radiobiological tumour and normal tissues response properties when optimizing the dose delivery. Generally traditional methods, using only dosimetrical measures, disregard the nonlinear radiation response of different tumours and normal tissues. The accumulated knowledge on tissue response to radiation, in the form of more accurate dose response relations, cell survival models and their associated biological parameters, alongside with the tools for biological treatment plan optimization, has allowed the present investigation on the potential merits of biologically based treatment optimization in radiation therapy.With a more widespread implementation of intensity modulated radiation therapy in the clinic, there is an increasing demand for faster and safer treatment delivery techniques. In this thesis biological treatment plan optimization, using the probability to achieve complication free tumour control as the quantifier for treatment outcome, was applied to radiation therapy of early breast cancer and advanced cervix cancer. It is shown that very conformal dose distributions can generally be produced with 3 or 4 optimally orientated coplanar intensity modulated beams, without having clinically significant losses in treatment outcome from the optimal dose distribution.By using exhaustive search methods, the optimal coplanar beam directions for intensity modulated photon beams for early breast cancer and the optimal non-coplanar directions for an advanced cervix cancer were investigated. Although time consuming, exhaustive search methods have the advantage of revealing most features involving interactions between a small number of beams and how this may influence the treatment outcome. Thus phase spaces may serve as a general database for selecting an almost optimal treatment configuration for similar patients. Previous knowledge acquired with physically optimized uniform beam radiation therapy may not apply when intensity modulated biological optimization is used. Thus unconventional treatment directions were sometimes found.

La policia sueca ha puesto en marcha un programa educativo de resistencia al abuso de drogas destinado a los alumnos de 7o, 8o y 9o, siendo los propios agentes quienes se encargan de ponerlo en practica dentro de las aulas. Los autores de este estudio han analizado los efectos del programa VAGA, una version del DARE (Drug Abuse Resistance Education) americano. Alrededor de 1.800 alumnos suecos de 22 centros de ensenanza secundaria respondieron en tres ocasiones diferentes, de forma anonima, a una serie de preguntas relacionadas con sus actitudes y experiencias con las drogas. La curiosidad y la accesibilidad que perciben los jovenes de esas edades en relacion a las drogas ilegales tienen unos efectos estadisticamente significativos sobre las actitudes y las experiencias individuales de los alumnos con dichas sustancias. Ni las actitudes hacia las drogas ni las experiencias con las mismas de los que han participado en el programa DARE un ano antes difieren de las de los jovenes de su edad que no habian tomado parte en el programa. Finalizamos el estudio con una breve discusion sobre que medidas deberia tomar la policia para impedir la accesibilidad a las drogas y cual deberia ser su papel en las escuelas.

A simultaneous TG-DSC method has been used for the determination of the solubility of polyethylene glycols in ethanol-water solutions. As a comparison precipitation was studied in test tubes at cooling to 15 or 20°C as well as dissolution at heating to temperatures between 25 and 60°C. The results are shown in ternary diagrams for polyethylene glycols with molecular weights from 1500 to 35000.

An automated electrophoresis/staining system is advantageous in the design, evaluation and documentation of biomolecule purification processes. Its use from laboratory scale to industrial scale is demonstrated in three major purification processes: (i) superoxide dismutase production (processing 3.51 of a clarified yeast lysate), (ii) staphylococcal enterotoxin B production (processing 440 l of supernatant liquid from a cell culture), and (iii) monoclonal antibody production (processing 143 l of a supernatant liquid from a cell culture). The speed and convenience of the system provide advantages in process monitoring; automated silver staining (60 min) enabled the detection of

Interactions between a drug discriminative stimulus (D, 17.5 mg/kg of pentobarbital vs. N, saline) and exteroceptive stimulus conditions (light vs. dark) were examined in a T-maze, shock-escape task using conditioning procedures pertaining to the phenomena of “overshadowing” and “blocking”. From an operational point of view, in the “overshadowing” procedure the stimulus compound is introduced from the outset of the training, whereas in the “blocking” procedure the stimuli components are introduced sequentially. When the compound discriminations were established, dose-generalization tests with various doses of pentobarbital (range 5.6–17.5 mg/kg) as well as saline (1 ml/kg) were carried out under both elements (light and dark) of the exteroceptive stimulus dimension. Prior training with drug (D vs. N) neutralized the potential influence of the exteroceptive dimension (light vs. dark); conversely training with the exteroceptive stimuli prior to the drug training accentuated the control over behavior by the visual stimuli. Dose-generalization results intermediate to those described above were observed in the group trained to discriminate the stimulus compound (D plus light vs. N plus dark) from the outset of training. It may therefore be concluded that exteroceptive stimuli can compete with interoceptive drug stimuli for associative strength in the procedure used. Thus, the formal similarities between drug discriminative stimuli and more conventionally studied exteroceptive, sensory signals are furthered by the data.

In an open trial, the efficacy of intravenously administered ceftazidime was evaluated in 106 adult patients with urinary or respiratory tract infections, soft tissue infections, osteitis and septicaemia. The most commonly isolated pathogens were Escherichia coli, Pseudomonas spp. and Staphylococcus aureus. Of 85 organisms isolated before treatment, 79% were cleared and 15% were cleared but later relapsed often because of the underlying conditions. Clinical cure was achieved in 70%, improvement occurred in 25% of the patients and 6% failed to respond. Marked increases in serum creatinine occurred in three patients with pre-existing renal impairment treated with ceftazidime in unmodified dosage. Exanthema, diarrhoea or local thrombophlebitis was noted in 13 patients.

In order to evaluate the efficacy and safety of aztreonam in hospitalized patients with upper urinary tract infections (UTI), a comparative clinical study with cefuroxime was performed. 62/60% (aztreonam/cefuroxime) of the patients had a complicating factor, mostly obstructive uropathy. I.v. bolus injections were used at a dose of 1 g aztreonam or 1.5 g cefuroxime t.i.d., for a mean of 8.2 days (range: five to 14 days) except in patients with bacteraemia, who received a mean of 10.3 days (range: seven to 13 days) of therapy. 89% of the patients treated with aztreonam and 87% of those who received cefuroxime showed clinical cure and the bacteriological cure rate at one week post-therapy was 70% and 73% in the respective groups. The relapse/reinfection rate was high with both drugs; bacteriological cure at one month post-therapy was only 43% after aztreonam and 40% after cefuroxime. This suggests that these infections may need longer treatment times. Superinfections, mostly asymptomatic urinary colonization, occurred in 7% and 3%, respectively, and adverse reactions in 23% and 12%, respectively, of the patients treated with aztreonam or cefuroxime, the majority being mild and reversible and only 3% and 3%, respectively, requiring discontinuation of the therapy. The t 1/2 for aztreonam following a 1 g i.v. bolus was 2.0 h in six patients with creatinine clearance above 80 ml/min and 3.0 h in seven patients with creatinine clearance between 35-75 ml/min.