Real time monitoring of laser-induced thermal changes in cartilage in vitro by using snapshot FLASH

1. Removal of external K+ ions increases the amplitude of directly elicited twitch contractions of the mouse diaphragm (Nishimura et al., 1996). This increase depends on external Ca2+ ions. 2. We examined the effect of caffeine (2 mM) on this increase in twitch amplitude. The mouse diaphragm muscle was directly stimulated in the presence of d-tubocurarine (10 microM). 3. Caffeine increased the amplitude of twitches in a standard bathing solution. This effect was maintained in a solution without either K+ or Ca2+ ions but was abolished in a solution from which both ions were absent. Readdition of Ca2+ ions restored the potentiating effect of caffeine. 4. In the presence of caffeine, removal of both K+ and Ca2+ ions decreased the resting membrane potentials of muscle fibers to about -53 mV. The readdition of 2 mM Ca2+ ions restored the membrane potentials. 5. Twitch potentiation in the absence of external K+ ions was attenuated by 10 microM bepridil but not by 3 microM verapamil or 10 microM Cd2+ ions. 6. These results support the hypothesis that Na(+)-Ca2+ exchange can support twitch contraction during the inhibition of Na(+)-K(+)-ATPase activity. The influx of Ca2+ ions into the cells might be stored in the sarcoplasmic reticulum.     

Intensive care 1980-1995: change in patient characteristics, nursing workload and outcome

OBJECTIVE: To assess temporal changes in patient characteristics, nursing workload and outcome of the patients and to compare the actual amount of available nursing staff with the estimated needs in a medical-surgical ICU. DESIGN: Retrospective analysis of prospectively collected data. SETTING: A medical-surgical adult intensive care unit (ICU) in a Swiss university hospital. PATIENTS: Data of all patients staying in the ICU between January 1980 and December 1995 were included. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: The estimated number of nurses needed was defined according to the Swiss Society of Intensive Care Medicine (SGI) grading system: category I = one nurse/patient/shift (= 8 h), category II = one nurse/two patients/shift, category III = one nurse/three patients/shift. An intervention score (IS) was obtained, based on a number of specific activities in the ICU. There was a total of 35,327 patients (32% medical and 68% postoperative/trauma patients). Over time, the number of patients per year increased (1980/1995: 1,825/2,305, p < 0.001) and the length of ICU stay (LOS) decreased (4.1/3.8 days, p < 0.013). There was an increase in the number of patients aged > 70 years (19%/28%, p < 0.001), and a decrease in the number of patients < 60 years (58%/41%, p < 0.001). During the same time period, the IS increased two-fold. Measurement of nursing workload showed an increase over time. The number of nursing days per year increased (1980/1995: 7454/8681, p < 0.019), as did the relative amount of patients in category I (49%/71%, p < 0.001), whereas the portion of patients in category II (41%/28%, p < 0.019) and category III (10%/0%) decreased. During the same time period, mortality at ICU discharge decreased (9.0%/7.0%, p < 0.002). CONCLUSIONS: During the last 16 years, there has been a marked increase in workload at this medical-surgical ICU. Despite an increase in the number of severely sick patients (as defined by the nursing grading system) and patient age, ICU mortality and LOS declined from 1980 to 1995. This may be ascribed to improved patient treatment or care. Whether an increasingly liberal discharge policy (transfer to newly opened intermediate care units, transfer of patients expected to die to the ward) or a more rigorous triage (denying admission to patients with a very poor prognosis) are confounding factors cannot be answered by this investigation. The present data provide support for the tenet that there is a trend toward more complex therapies in increasingly older patients in tertiary care ICUs. Calculations for the number or nurses needed in an ICU should take into acount the increased turnover of patients and the changing patient characteristics.     

Radial BURST imaging

A radial BURST approach combining BURST excitations with projection reconstruction (PR) gradients for excitation and acquisition is introduced. With the application of PR gradients during excitation, the applied RF energy is distributed more homogeneously across the sample than in the initial BURST approach. Computer simulations of the radial BURST excitation scheme are presented and experimentally verified. Actual radial BURST implementation acquiring a 64 x 64 radial BURST image in 45 ms is reported. Extensions of the radial BURST imaging technique placing a magnetization preparation experiment in front of the whole imaging sequence are also described. Furthermore, the feasibility of combining radial BURST with a multishot approach is demonstrated.     

Factors affecting homologous overexpression of the Saccharomyces cerevisiae lanosterol 14 alpha-demethylase gene.

The Saccharomyces cerevisiae Lanosterol 14 alpha-demethylase (14DM) gene was overexpressed in S. cerevisiae using promoter sequences of the highly expressed S. cerevisiae glyceraldehyde-3-phosphate dehydrogenase (TDH3) gene. To investigate factors affecting 14DM overproduction, the levels of 14DM-specific RNAs, apoprotein, and heme protein, respectively, were determined and the 14DM-specific RNA levels compared with the RNA levels originating from the endogenous TDH gene(s). The quantitative measurements revealed that the 14DM steady-state RNA levels reached were some three- to five-fold below the theoretically expected values. With a view towards further improving expression of the 14DM gene, the spacing between the TDH3 promoter and the AUG was adjusted precisely and to rule out possible toxic effects exerted by the 14DM protein, the TDH3 promoter was placed under galactose regulation by introducing an UASG segment. Furthermore, the effects of the gene copy number on 14DM overproduction were investigated. From the analysis of the improved expression constructs five conclusions could be reached: (1) expression from the native 14DM gene is comparable to the expression driven by the TDH3 promoter-14DM fusion construct on single copy plasmid vectors; (2) expression from the TDH3 promoter-14DM construct on single-copy vectors is nearly as efficient as expression from the corresponding endogenous TDH3 gene; (3) the gene copy number has an effect on the relative expression levels of the TDH3 promoter-14DM constructs; (4) the steady-state amounts of protein produced are very nearly proportional to gene dosage; and (5) protein toxicity does not have a major impact on 14DM production. The maximum yield of 14DM was in the order of 7% of the total yeast protein and the maximum production of functional 14DM heme protein appears to be limited by the availability of heme.     

Site‐Specific Labelling of Native Mammalian Proteins for Single‐Molecule FRET Measurements

Human cells are complex entities in which molecular recognition and selection are critical for cellular processes often driven by structural changes and dynamic interactions. Biomolecules appear in different chemical states, and modifications, such as phosphorylation, affect their function. Hence, using proteins in their chemically native state in biochemical and biophysical assays is essential. Single‐molecule FRET measurements allow exploration of the structure, function and dynamics of biomolecules but cannot be fully exploited for the human proteome, as a method for the site‐specific coupling of organic dyes into native, non‐recombinant mammalian proteins is lacking. We address this issue showing the site‐specific engineering of fluorescent dyes into human proteins on the basis of bioorthogonal reactions. We show the applicability of the method to study functional and post‐translationally modified proteins on the single‐molecule level, among them the hitherto inaccessible human Argonaute 2.     

Reappraising the Luminescence Lifetime Distributions in Silicon Nanocrystals

The luminescence dynamics in ensembles of nanocrystals are complicated by a variety of processes, including the size-dependence of the radiative and non-radiative rates in inhomogeneous broadened samples and interparticle interactions. This results in a non-exponential decay, which for the specific case of silicon nanocrystals (SiNCs) has been widely modeled with a Kohlrausch or “stretched exponential” (SE) function. We first derive the population decay function for a luminescence decay following exp[??(t/τ)^β]. We then compare the distributions and mean times calculated by assuming that either the luminescence decay or the population decay follows this function and show that the results are significantly different for β much below 1. We then apply these two types of SE functions as well as other models to the luminescence decay data from two thermally grown SiNC samples with different mean sizes. The mean lifetimes are strongly dependent on the experimental setup and the chosen fitting model, none of which appears to adequately describe the ensemble decay dynamics. Frequency-resolved spectroscopy (FRS) techniques are then applied to SiNCs in order to extract the lifetime distribution directly. The rate distribution has a half width of ~?0.5 decades and mainly resembles a somewhat high-frequency-skewed lognormal function. The combination of TRS and FRS methods appear best suited to uncovering the luminescence dynamics of NC materials having a broad emission spectrum.     

The influence of spinel and magnesia powder bed on mechanical properties of alumina sintered under air and nitrogen atmosphere

ABSTRACT

The aim of the present work was changing the surface properties of alumina ceramic via sintering of samples in spinel MgAl₂O₄ and magnesia MgO powder bed. During sintering nitrogen and air atmosphere were used; and the reference material was sintered at the same conditions but in an alumina powder bed. All samples were sintered to a density higher than 99.2% of theoretical density of alumina. In order to examine samples SEM, EDX and XRD (X-ray diffraction from 18 to 70 °2Theta) analysis were performed together with B3B flexural strength measurement. Results revealed that by sintering of alumina samples in a spinel powder bed pore-free surfaces were prepared, which had a favourable effect on B3B flexural strength. This was ascribed to the high solubility of Al³⁺ in spinel at sintering temperatures, which increases the sintering driving force. A further positive effect on B3B flexural strength was observed when samples were sintered in nitrogen instead of air.     

Coherent processing of character skeletal forms

It is well known that in the general context the similarity relation is very fuzzy and hard to define. Unfortunately, the intuitive notion of similarity is not a transitive relation: knowing that A is similar to B and that B is similar to C does not necessarily imply similarity between A and C. This is a main obstacle when trying to express formally what a coherent font design is. In this paper we suggest a method to decompose complex letter forms into simpler elements and we suggest a formal transitive definition of a similarity relation between these elements. In the context of digital typography, this definition enables developing an algorithm to recover classes of similar elements within different characters of a given font. This knowledge is further exploited to ensure coherent type processing. For example, a modification (e.g. by a type designer) of a character element is propagated automatically to all the other characters that include a similar element. For the moment, the discussion is limited to the class of stroke fonts.     

Scattering phase shifts in Ni and Zn doped Y-123

Cu-site substituted thin films of YBa₂(Cu_1-zM_z)₃O_7- (M=Zn,Ni) are reinvestigated. The T_c-suppression and residual resistivities o are measured as a function of the concentration z. We found that for low concentrations z < 4% the substituents occupy preferrably the in-plane Cu sites whereas for higher concentrations the chain sites are also occupied. Although the residual resistivities of Ni and Zn differ only slightly, the T_c-suppression of Zn is 2.3 times larger than that of Ni. To reconcile the measured resistivities with predictions of a two dimensional scattering model, it is necessary to assume a scattering potential of finite range and to take scattering phase shifts] _l of higher angular momentum (l > 0) into account. The different T_c-suppression rates for Zn and Ni are also discussed within this picture.