Asphalt modified by SBS triblock copolymer: Structures and properties

Microstructural transformation of a poly(styrene-b-butadiene-b-styrene), SBS, triblock copolymer blended with asphalt was studied as the asphalt composition was varied from 0 wt% to 96 wt%. Transmission electron microscopy (TEM), dynamic mechanical spectrometry (DMS), and differential scanning calorimetry (DSC) were used. The blends were made in batch mixers at 200°C, or by solution casting from a nonselective solvent (trichloroethane) at ∼28°C. Asphalt partially solubilizes the polybutadene (PB) midblock of the SBS producing saturated PB microdomains along with macrodomains of asphalt. When the asphalt concentration was varied from 10 to 90 wt%, the asphalt phase separated into a variable number of large domains, while the SBS-rich regions formed a continuous matrix. Networks of SBS-rich regions were observed at low magnification; these are referred to as macro-networks. At higher magnification, networks that are stabilized by polystyrene (PS) microdomains (denoted micro-networks) are also formed. The presence of a macro-network is also confirmed by stress relaxation tests. The macro-network broke down into microgel-like structures when the asphalt composition exceeded 90 wt%. Examination of the interior of the SBS-rich regions showed that the shape of the PS microdomains transformed from short cylinders to lamellae, hexagonally perforated lamellae (HPL), back to lamellae, short cylinders, and finally to spheres. DMS and DSC indicate a systematic increase in the PB glass transition temperature (T_g) and negligible change in the T_g of PS as the asphalt content increases. Triblock copolymers that can form a macro-network at low concentration will be more desirable for highway pavement modification.     

Potassium availability with application of sewage sludge,and sludge and manure composts in field experiments

An experiment was conducted to determine the plant availability of K in organic wastes. Four materials: digested sewage sludge (DSS), digested irradiated sludge (DISS), digested, irradiated and composed sludge (DICSS), and composted livestock manure (CLM) were applied to farmland for two years at rates of 10, 20, 30, and 40 mg-solids ha^–1 yr^–1. Potassium fertilizer (KCl) was added to the control treatment (CT), to which no waste was applied, and to the low-rate waste applications, to meet crop K requirement. Equal yields within different treatments were obtained for the test crops lettuce and snap beans through application of available N at the levels balanced for crop economical production. Potassium from the wastes was evaluated based on the assumption that Crop K uptake/Available K applied was equal between the CT and waste treatments. The results indicated that, in general, K applied with wastes (waste K + fertilizer K) was equally available (101±7%) to fertilizer K (KCl), except for low rate application of DISS (10 Mg ha^–1), where the availability of K was low (89±1%).     

Comparison of multiplex PCR with conventional biochemical methods for the identification of Listeria spp. isolates from food and clinical samples in Queensland, Australia

Listeria monocytogenes is an important foodborne pathogen with high mortality. L. monocytogenes and five other Listeria species can frequently be found in the same sample. To identify Listeria isolates found in foods to the species level, two multiplex PCRs were designed. The PCR and conventional biochemical methods were compared for the identification of 456 Listeria isolates collected from routine food quality monitoring schemes between June 2004 and February 2006 and for 62 L. monocytogenes isolates from patients between 1999 and 2005. The results showed that the PCR and biochemical methods had 100% agreement in Listeria identification. The distribution of Listeria species from foods was as follows: L. monocytogenes, 50.4%; L. innocua, 33.8%; L. welshimeri, 14.9%; L. seeligeri, 0.7%; L. grayi, 0.2%; and L. ivanovii, 0.0%. Additional analyses were performed to identify the major serotypes (1/2a, 1/2b, 1/2c, and 4b) and the three lineages of L. monocytogenes isolates from foods and patients, with 1/2a (69.6%) and 1/2b (21.7%) dominating the food isolates and 1/2b (54.8%) and 4b (30.7%) dominating the patient isolates. The lineage results showed that isolates of 1/2a and 1/2c belonged to lineage II and that isolates of 1/2b and 4b belonged to lineage I. The multiplex PCRs for Listeria identification that have been established provide an accurate and rapid method for food quality control. This study has provided the basic knowledge of distribution of Listeria species and L. monocytogenes serotypes in Queensland, Australia, which is useful for epidemiological investigations of listeriosis.     

Upper bound risk estimates for mixtures of carcinogens

The excess cancer risk that might result from exposure to a mixture of chemical carcinogens usually is estimated with data from experiments conducted on individual chemicals. An upper bound on the total excess risk is estimated commonly by summing individual upper bound risk estimates. The degree to which this approach might overstate the true risk associated with the mixture has not been evaluated previously. This paper reports the results of a Monte Carlo simulation study on the degree of reduction in conservation that might be achieved using alternative methods for calculating mixture upper bounds. An unexpected finding is that for chemicals that exhibit strongly linear dose-response relationships, the summing of multistage-model-based upper bounds on excess risk can be anti-conservative, that is, it can provide less than the nominal 100(1-alpha)% coverage.     

Potential role of luminal potassium in tubuloglomerular feedback

Transport through the Na+-2Cl(-)-K+ cotransporter in the luminal membrane of macula densa cells is considered critical for tubuloglomerular feedback (TGF). Although various studies could support the importance of luminal Na+ and Cl-, the role of luminal K+ in TGF has not been thoroughly addressed. The study presented here examines this issue in nephrons with superficial glomeruli of anesthetized male Munich-Wistar-Fr?mter rats. Ambient Na+ concentration in early distal tubular fluid was approximately 22 mM, suggesting collection sites relatively close to the macula densa segment. First, it was found that ambient early distal tubular K+ concentration is approximately 1.3 mM, i.e., close to the K+ affinity of the Na+-2Cl(-)-K+ cotransporter in the thick ascending limb. Second, it was observed that a change in late proximal tubular flow rate, i.e., a maneuver that is known to induce a TGF response, significantly alters early distal tubular K+ concentration. Third, previous experiments failed to show an inhibition in TGF response during retrograde perfusion of the macula densa with K+-free solutions. Because of a potential K+ influx into the lumen between the perfusion site and the macula densa, however, the K+ channel blocker U37883A was added to the K+-free perfusate. TGF response was assessed as the fall in nephron filtration rate in response to retrograde perfusion of the macula densa segment from early distal tubular site. It was observed that luminal U37883A (100 microM) significantly attenuated TGF. Because adding 5 mM KCl to the perfusate restored TGF in the presence of U37883A and because the inhibitory action of U37883A on tubular K+ secretion was confirmed, the effect of U37883A on TGF was most likely caused by inhibition of K+ influx into the perfused segment, which decreased luminal K+ concentration at the macula densa. The present findings support a potential role for luminal K+ in TGF, which is in accordance with a transmission of the TGF signal across the macula densa via Na+-2Cl(-)-K+ cotransporter.     

Cerebral palsy: a comprehensive review

Cerebral palsy is a broad range of static, nonprogressive motor disabilities that present from birth or early childhood as a result of injury to neuromotor components of the central nervous system. Motor performance is normally coordinated via communication between the cerebral cortex, thalamus, basal ganglia, brain stem, cerebellum, spinal cord, and communicating sensori-motor pathways. This complex network lends itself to injury at many different levels. Etiologies are numerous and can occur during the prenatal, perinatal, and postnatal periods. The severity of the neurologic deficit and the clinical manifestations are varied depending on the time, location and nature of the original injury. In order to approach cerebral palsy systematically, the primary health care practitioner must be prepared to recognize neuromotor deficits, diagnose and classify the type of disorder, and implement a methodical treatment plan. The purpose of this article is to review the etiology, pathophysiology, diagnostic classification (Swedish system), clinical manifestations, and therapeutic management of cerebral palsy and prepare the advanced practice nurse to care for the individual and family.     

Alzheimer's disease and its Lewy body variant: a clinical analysis of postmortem verified cases

OBJECTIVE: The authors compared clinical findings of Alzheimer's disease and the so-called Lewy body variant of Alzheimer's disease. METHOD: Available data were analyzed on the clinical features of 58 patients with Alzheimer's disease and 24 patients with the Lewy body variant of Alzheimer's disease who underwent postmortem examination. RESULTS: The proportion of men was significantly larger in the Lewy body variant group than in the Alzheimer's disease group (66.7% versus 34.5%), and, concordantly, the Lewy body variant group was slightly taller. The prevalence of hallucinations and delusions was significantly higher in Lewy body variant subjects than the Alzheimer's disease subjects, but there were no significant differences between the two groups in educational attainment, family history of dementia, age at onset, duration of illness, cognitive impairment, overall severity of illness, or neuropsychological findings. Patients with the Lewy body variant of Alzheimer's disease tended to experience more frequent extrapyramidal side effects of neuroleptics than did the patients with Alzheimer's disease, but for patients in the two groups who were not exposed to neuroleptics, there was little difference in frequency of extrapyramidal side effects. CSF concentration of homovanillic acid (HVA) was significantly lower in the Lewy body variant patients, even when correction was made for height. CONCLUSIONS: The Lewy body variant of Alzheimer's disease may be suspected in elderly male dementia patients who otherwise meet criteria for Alzheimer's disease but who manifest significant psychiatric symptoms and neuroleptic-induced extrapy-ramidal side effects and have low levels of CSF HVA.