A failure criterion for brittle elastic materials under mixed-mode loading

The failure criterion of Leguillon at reentrant corners in brittle elastic materials (Leguillon 2002, Eur J Mech A/Solids 21: 61–72; Leguillon et al. (2003), Eur J Mech A—Solids 22(4): 509–524) validated in (Yosibash et al. 2004, Int J Fract 125(3–4): 307–333) for mode I loading is being extended to mixed mode loading and is being validated by experimental observations. We present an explicit derivation of all quantities involved in the computation of the failure criterion. The failure criterion is validated by predicting the critical load and crack initiation angle of specimens under mixed mode loading and comparison to experimental observations on PMMA (polymer) and Macor (ceramic) V-notched specimens.     

The design of optimal reduced order stochastic observers fordiscrete-time linear systems

The minimum variance state estimation of linear discrete-time systems with random white noise input and partially noisy measurements is investigated. An observer of minimal-order that attains the minimum-variance estimation error is found. The structure of this observer is shown to depend strongly on the geometry of the system. This geometry dictates the length of the delays that are applied on the measurements in order to obtain the optimal estimate. The transmission properties of the observer are investigated for systems that are left invertible and free of measurement noise. An explicit expression is found for the transfer function matrix of the observer, from which a simple solution to the linear discrete-time singular optimal filtering problem is obtained     

The design of optimal reduced-order stochastic observers fordiscrete-time linear systems

The minimum-variance-state estimation of linear discrete-time systems with random white-noise input and partially noisy measurements is investigated. An observer of minimal order is found which attains the minimum-variance estimation error. The structure of this observer is shown to depend strongly on the geometry of the system. This geometry dictates the length of the delays that are applied on the measurements in order to obtain the optimal estimate. The transmission properties of the observer are investigated for systems that are left invertible, and free of measurement noise. An explicit expression is found for the transfer-function matrix of this observer, from which a simple solution to the linear discrete-time singular optimal filtering problem is obtained     

Characterization of DNA topoisomerase activity in two strains of Mycoplasma fermentans and in Mycoplasma pirum

DNA topoisomerases (topos) are essential enzymes that participate in many cellular processes involving DNA. The presence of the DNA-gyrase genes in various mycoplasmas has been reported elsewhere. However, the characterization of DNA topo activity in mycoplasmas has not been previously undertaken. In this study, we characterized the topo activity in extracts of Mycoplasma fermentans K7 and incognitus and in Mycoplasma pirum, as well as in partially purified extract of M. fermentans K7. The topo activity in these microorganisms had the following properties. (i) The relaxation of supercoiled DNA was ATP dependent. (ii) ATP independent relaxation activity was not detected. (iii) Supercoiling of relaxed topoisomers was not observed. (iv) The relaxation activity was inhibited by DNA gyrase and topo IV antagonists (novobiocin and oxolinic acid) and by eukaryotic topo II (m-AMSA [4'-(9-acridylamino)methanesulfon-m-anisidide]) and topo I antagonists (camptothecin). Other eukaryotic topo II antagonists (teniposide and etoposide) did not affect the topo relaxation activity. (v) Two polypeptides of 66 and 180 kDa were found to be associated with the mycoplasma topo activity. These results suggest that the properties of the topo enzyme in these mycoplasma species resemble those of the bacterial topo IV and the eukaryotic and the bacteriophage T4 topo II. The findings that mycoplasma topo is inhibited by both eukaryotic topo II and topo I antagonists and that m-AMSA and camptothecin inhibited the growth of M. fermentans K7 in culture support our conclusion that these mycoplasma species have topo with unique properties.     

Effects of cognitive load on semantic priming in patients with schizophrenia.

Schizophrenic and control participants received 2 blocks of trials in each experiment. In 1 block they were exposed to regular priming trials (doctor–nurse), and in another block a nonlexical probe was presented at prime onset for 40 ms. Regardless of stimulus onset asynchrony (SOA), the schizophrenic patients showed hyperpriming when no distractor was present. Paying attention to the distracting stimulus reduced priming in the patient group irrespective of SOA. Under certain situations, the reduction in priming appeared even when participants were asked to ignore the distracting stimulus. Thus, even a nonsemantic distractor may be detrimental to schizophrenic patients' language processing. That SOA did not modulate the reduction in priming effect is consistent with the suggestion that attentional resources are required even with short prime–target intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two maternal representations: A study of Israeli adopted children.

Using an object relations perspective, the representations of birth and adopted mothers in a sample of 52 nonreferred adoptees were studied. To better understand the specific effects of adoption or, the construction of 2 maternal representations, birth and adoptive maternal representation of adopted children was compared with that of nonadopted children. In addition, the effect of incongruous representations of birth and adoptive mothers on adoptees' exteralizing and internalizing behaviors was explored. Compared with nonadopted children, adoptees' representations of the mothers appear as more concrete and less benign. Among adopted children, representations of the birth mothers were found to contain split negative aspects of the adoptive mothers. Moreover, the differences between birth and adoptive mother representations were found to associate with adoptees'externalizing behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Thermostat with Short- and Long-Term Stability of ± 1.5×10−4°C

The design of a thermostat which gives a temperature stability of ± 1.5 × 10^?4°C over a period of weeks is described. The temperature sensors are thermistors stabilized by heat treatment. Heat input derives mainly from stirring and heat output mainly from losses to the surroundings. Residual heat input is removed by stabilized circulating thermostats. Temperature balance is due to spread out bare wire heaters which carry a current proportional to the state of the control DC Wheatstone bridge. The controlling thermistors are maintained in two oil baths and the state of the current in the control heaters is transmitted to the thermistors by a thermal feedback system involving small heating coils which are placed in the oil baths around the thermistors and which carry a current proportional to the heating current.     

Regions of pole location of the discrete stationary Kalman filter

Two regions are found inside the complex unit circle that exclude all the poles of the discrete stationary Kalman filter. The sizes of these regions depend on the ratio between the intensities of the signal and the measurement noise, and in the limit where this ratio tends to infinity, one of the regions shrinks to the origin.     

Fluorescence-based zinc ion sensor for zinc ion release from pancreatic cells

In this paper, we describe the synthesis and characterization of analytical properties of fluorescence-based zinc ion-sensing glass slides and their application in monitoring zinc ion release from beta pancreatic cells in cell cultures. To fabricate the sensors, the zinc ion indicator ZnAF-2 {6-[N-[N',N'-bis(2-pyridinylmethyl)-2-aminoethyl]amino-3',6'-dihydroxyspiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one} was modified to include a sufficiently long linking aliphatic chain with a terminal carboxyl functional group. The recently synthesized ZnAF-2 zinc ion indicator provided high zinc ion selectivity in physiological solutions containing millimolar levels of calcium and other possible interfering cations. The carboxyl-modified ZnAF-2 was conjugated to the activated surface of glass slides, which then served as zinc ion sensors. It was possible to grow pancreatic cells directly on the zinc-sensing glass slide or on a membrane placed on these glass slides. The sensors were used to monitor zinc ion release events from glucose-stimulated pancreatic cells. The study showed that the zinc ion sensors responded effectively to the release of zinc ions from pancreatic cells at the nanomolar level with high selectivity and rapid subsecond response time.