Interaction of cell culture with composition effects on the mechanical properties of polycaprolactone-hydroxyapatite scaffolds fabricated via selective laser sintering (SLS)

In the current study PCL/HA composites were fabricated using SLS as two- and three-dimensional lattice structures and exposed to a cellular component (MC 3T3 osteoblast-like cells). The main aims were to determine the mechanical differences due to powder composition and to observe the physical and mechanical changes pertaining to cell presence. These structures were characterized by compressive mechanical testing, and the effects of cell culturing and degradation on mechanical properties of the scaffolds with different PCL/HA compositions were determined. Moreover, changes in the scaffold morphology due to the cell culture conditions were determined by μ-CT analysis.Cells steadily grew on the scaffolds for 21 days with preferential distribution around the macropores and initially PCL/HA(15%) composites had higher cell numbers. Removal of loosely sintered parts was observable during the culturing period. Cell culture conditions did not change the compressive moduli significantly but had a distinct effect on compressive strength. For PCL/HA(15%) composites, an initial loss in strength caused by cell culture was reversed by longer cell exposure, with compressive strength of the structures restored to the initial properties (p ≤ 0.05). μ-CT measurements showed widespread morphological changes in the scaffolds, such as a decrease in the roughness of the struts. In general, in the initial period composites with lower HA content (15 wt.%) showed better metabolic activity compared to the higher HA content, however by day 14 the performance of the two compositions was equal. These results suggest that changes in sintering due to the differences in powder composition can have profound effects on the short and long term mechanical properties of the scaffold particularly under cell culture conditions, and this should be closely considered for SLS processing of scaffolds.     

DC Kiln Drive Motors

The most important considerations in applying dc drive motors and thyristor power supplies to a cement kiln are their procurement, maintenance, and operating costs; and equipment reliability in the cement plant environment. Drive requirements and their effect on motor size are discussed. Efficiency comparisons at several speeds for three different designs of dc drive motors are made. Two motor kiln drives with motors connected in series and also in parallel are discussed. Recommendations for applying each connection with regard to drive horsepower and voltage are made. Included is a brief discussion on applying dc motors by taking a part of the total speed range as constant horsepower rather than taking the entire speed range as constant torque.     

Emotional imagery in simple and social phobia: Fear versus anxiety.

In a 1st study, 60 phobic volunteer Ss reacted psychophysiologically with greater vigor to imagery of their own phobic content than to other fearful or nonaffective images. Imagery heart rate responses were largest in Ss with multiple phobias. For simple (dental) phobics, cardiac reactivity was positively correlated with reports of imagery vividness and concordant with reports of affective distress; these relationships were not observed for social (speech) phobics. In a 2nd study, these phobic volunteers were shown to be similar on most measures to an outpatient clinically phobic sample. In an analysis of the combined samples, fearful and socially anxious subtypes were defined by questionnaires. Only the fearful subtype showed a significant covariation among physiological responses, imagery vividness, and severity of phobic disorder. This fearful–anxious distinction seems to cut across diagnostic categories, providing a heuristic perspective from which to view anxiety disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Letters from the heart: Affective categorization of letter combinations in typists and nontypists.

In 2 experiments, typists and nontypists affectively evaluated pairs of letter combinations in a forced-choice paradigm. Within each pair, one combination would be typed with the same finger and the other with different fingers. Compared with nontypists, typists more frequently preferred letter combinations typed with different fingers to combinations typed with the same finger. However, when requested to differentiate cognitively between the members of a pair, typists were not able to detect the categorical difference. These findings point to the involvement of automatically activated motor information in memory even in the absence of an intentional set for actually executing the movement. Affective evaluation of letter combinations appears to be a conscious construction making use of this automatically activated motor information. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Neurotoxic effect of cisplatin and the cisplatin-procaine complex DPR studied in organotypic cultures of chick embryonic dorsal root ganglia

Neurotoxic effects of cisplatin and the cisplatin-procaine complex cis-diaminechloro-[2-(diethylamino)ethyl 4-aminobenzoate, N4]-chlorideplatinum(II) monohydrochloride monohydrate (DPR) were compared in organotypic cultures of chick embryonic dorsal root ganglia maintained in a semi-solid (soft agar) culture medium. The changes of two characteristics of the neurite outgrowth, the mean radial length of neuritic processes growing out from the ganglia and the area of neurite outgrowth around the ganglion, were used as parameters to evaluate the toxic effect of both compounds. The drugs were administered to the cultures at concentrations ranging from 13 to 120 microM. The half-maximum inhibition concentration (IC50) was determined from the concentration-response curves for both the mean radial length of neurites and the area of neurite outgrowth. An analysis of these parameters revealed that DPR was significantly less neurotoxic than cisplatin. In fact, considering the mean radial length of neurite processes, the IC50s of cisplatin were 56, 65 and 66 microM after 24, 48 and 72 h of exposure, respectively. By contrast, for DPR the IC50s were 116 microM after 24 h, and greater than 120 microM after 48 and 72 h of exposure. When we considered the area index (i.e. the area of neurite outgrowth normalized for the area of the ganglia), the IC50s for cisplatin were 41, 52 and 55 microM after 24, 48 and 72 h of exposure, respectively, whereas for DPR the IC50s were 59 microM after 24 h, and greater than 120 microM after 48 and 72 h of exposure. Our results support previous findings of lower toxicity of DPR to non-neoplastic tissues, as compared to cisplatin.     

A computer architecture laboratory course using programmable logic

This paper describes the software and hardware developed for the laboratory component of a junior/senior level computer architecture course. The principal feature of this course is that students are required to design and build their own computers using programmable logic devices (PLDs). The students use a simple register transfer language (CURTL) with a simulator and commercial PLD tools for their design activity. A graphical PC based debugging tool provides the I/O and main memory for the student built computers     

Magnitude and duration of cardiovascular response to anger in Vietnam veterans with and without posttraumatic stress disorder.

This study investigated the cardiovascular responses to a relived anger task in 118 male Vietnam combat veterans (62 with posttraumatic stress disorder [PTSD] and 56 without PTSD). Participants completed standardized diagnostic measures, hostility measures, and a laboratory session in which they relived a self-chosen anger memory while heart rate (HR), systolic blood pressure, and diastolic blood pressure (DBP) were measured continuously using an Ohmeda Finapres monitor. Compared with veterans without PTSD, PTSD veterans took less time to feel anger, had greater mean HR and DBP response during relived anger, and reported greater anger and anxiety during the task. There was a significant relationship between covert hostility and anger response during and after the anger task only in participants with PTSD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biochemical studies of the thermal effects on DNA modifications by the antitumor cisplatin and their repair

Using biochemical methods, we have examined the effect of two factors that might play a role in the mechanism of the biological activity of cisplatin at elevated temperatures (>37 degrees C). We show that increased temperatures result in distinct alterations in the modification of the target DNA by cisplatin, and in the repair of these modifications. Our in vitro results support the view that the enhanced DNA-cross-linking efficiency of cisplatin and the lower efficiency of native DNA repair mechanisms at higher temperature play at least a partial role in the potentiation of the antitumor effects of cisplatin under conditions of mild hyperthermia.     

Through-the-thickness residual stress analysis by neutron diffraction in inoxidizable martensitic steel samples with and without tungsten carbide coating

The residual stress (RS) induced in the substrate by thermal spray-coating plays a significant role in the behaviour of coated materials. The characterisation of High-Velocity Oxy-Fuel (HVOF) coatings through RS determination justifies various cases of failure or bad performance due to the delamination of coating which is not easily interpretable through more traditional microstructural analyses and mechanical tests.Two 13Cr4Ni inoxidizable martensitic steel samples, one having a thermal spray (WC–12% Co) HVOF coated surface, the other a shoot peened surface, were analyzed by neutron diffraction (ND) in order to determine the real RS depth-profile and investigate the effects of the thermal process on the considered materials.The stresses resulted in the range from − 80 to 50 MPa for the uncoated sample, while for the coated sample they increased gradually from a slight compressive status in correspondence of the uncoated surface, to greatest values of ~ 250 MPa in correspondence of the coating. A traditional X-ray investigation on the coated surface measured compressive RS values σ = − 550 ± 40 MPa, showing that ND investigation is very suitable for critical applications, where a much greater stress situation could be present at a diverse depth.The results achieved yielded trends that can be used in monitoring of the coating characteristics, in particular adhesion, thereby confirming the relevance of thermal stresses induced by HVOF coating processes.