A Bose-atom model for heavy deuterium halides

A Bose-atom model is introduced for the molecule DH where H represents a heavy halogen atom. A potential is constructed for this system and corresponding wavefunctions and energies are obtained. In the ground state, the large mass of the deuteron causes large penetration into the ion core. An expression for the probability of deuteron-nuclear overlap is obtained of the form $\text{P = (1.4r}{}_{\mathrm{<mtext>N</mtext>}}\text{/a}{}_0\text{)}{}^{\mathrm{2f}}\text{/4√πf}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ where r_N is nuclear radius, a₀ is Bohr radius, Z is atomic number and $\text{f = √}\text{2Zm}{}_{\mathrm{<mtext>d</mtext>}}\text{m}{}_{\mathrm{<mtext>e</mtext>}}\text{? 1}$. Thus P is infinitesimally small. Relevance to the exothermic reaction ¹²⁷I(d,n) ¹²⁸Xe is discussed.     

Prevalence of microbial biofilms on selected fresh produce and household surfaces

Investigations of biofilms in domestic environments are sparsely represented in the literature. In this study, samples of various household surfaces, including food, laundry and kitchen items, were analyzed for evidence of biofilm presence. Visualization of the surfaces was carried out using cryostage scanning electron microscopy (CSEM) and light microscopy. Qualitative evidence of the presence of biofilm formation was obtained from all of the sample groups analyzed, suggesting the widespread existence of microorganisms in biofilms on domestic surfaces. This suggests that biofilms may be important in household hygiene, and highlights the need for standardized, approved biofilm methods suitable for consumer products testing.     

The role of adverse weather conditions in acute releases of hazardous substances, Texas, 2000-2001

High winds, flooding, lightning, and other phenomena associated with adverse weather can cause power failures, equipment damage, and process upsets resulting in chemical releases. Of the 5000 events in Texas that were reported to the Hazardous Substances Emergency Events Surveillance (HSEES) system during 2000-2001, adverse weather conditions contributed to 110 (2%) events. Rain was the most frequent adverse weather condition. Most events to which adverse weather conditions contributed occurred during June or September; these months correspond with the high temperature and hurricane season in Texas. Most events occurred in coastal counties with large numbers of industrial facilities. Three industries reported the majority of events: industrial and miscellaneous chemicals manufacturing; petroleum refining; and plastics, synthetics, and resin manufacturing. Power failures were associated more often with adverse weather-related events than with nonweather-related events. Releases occurred most commonly from ancillary process equipment and process vessels. Events associated with adverse weather-related conditions involved nine victims. System and process design improvements, such as improved backup power generation and redesigned secondary containment systems, could be explored to reduce the potential negative effects of severe weather.     

Preparation and characterization of two new dielectric ceramics Ba4NdTiNb3O15 and Ba3Nd2Ti2Nb2O15

Two new cation-deficient hexagonal perovskites Ba₄NdTiNb₃O₁₅ and Ba₃Nd₂Ti₂Nb₂O₁₅ were prepared in the BaO–Nd₂O₃–TiO₂–Nb₂O₅ system by high temperature solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction and scanning electron microscope (SEM). The microwave dielectric properties of the ceramics were studied using a network analyzer. Ba₄NdTiNb₃O₁₅ has a dielectric constant of 38.15, a high-quality factors (Q _u ×f >18 700 at 5.4422 GHz), and a small temperature coefficient of resonant frequency ( _f )+12 ppm °C^–1 at room temperature; Ba₃Nd₂Ti₂Nb₂O₁₅ has a higher dielectric constant of 46.83 with high-quality factors Q _u ×f >19 500 at 5.0980 GHz, and _f +28 ppm °C^–1.     

Characterization and dielectric properties of Sr4La2Ti4M6O30 (M=Nb, Ta) ceramics

Sr₄La₂Ti₄M₆O₃₀ (M=Nb or Ta) compounds were synthesized by the conventional powder compaction and high temperature solid state reaction technique. The dielectric properties of the sintered samples were measured and they were further characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. Sr₄La₂Ti₄M₆O₃₀ compounds are paraelectric phases adopting filled tetragonal tungsten–bronze (TB) structure at room temperature. Sr₄La₂Ti₄Nb₆O₃₀ and Sr₄La₂Ti₄Ta₆O₃₀ show high dielectric constants of 387 and 166 together with low dielectric loss of 0.0084 and 0.0042 at 1 MHz, respectively.     

A new method for defining and managing process alarms and for correcting process operation when an alarm occurs

A new mathematical treatment of alarms that considers them as multi-variable interactions between process variables has provided the first-ever method to calculate values for alarm limits. This has resulted in substantial reductions in false alarms and hence in alarm annunciation rates in field trials. It has also unified alarm management, process control and product quality control into a single mathematical framework so that operations improvement and hence economic benefits are obtained at the same time as increased process safety. Additionally, an algorithm has been developed that advises what changes should be made to Manipulable process variables to clear an alarm. The multi-variable Best Operating Zone at the heart of the method is derived from existing historical data using equation-free methods. It does not require a first-principles process model or an expensive series of process identification experiments. Integral with the method is a new format Process Operator Display that uses only existing variables to fully describe the multi-variable operating space. This combination of features makes it an affordable and maintainable solution for small plants and single items of equipment as well as for the largest plants. In many cases, it also provides the justification for the investments about to be made or already made in process historian systems. Field Trials have been and are being conducted at IneosChlor and Mallinckrodt Chemicals, both in the UK, of the new geometric process control (GPC) method for improving the quality of both process operations and product by providing Process Alarms and Alerts of much high quality than ever before. The paper describes the methods used, including a simple visual method for Alarm Rationalisation that quickly delivers large sets of Consistent Alarm Limits, and the extension to full Alert Management with highlights from the Field Trials to indicate the overall effectiveness of the method in practice.     

In vivo characterisation of a novel bioresorbable poly(lactide-co-glycolide) tubular foam scaffold for tissue engineering applications

Polylactide-co-glycolide (PLGA) foams of tubular shape were assessed for their use as soft-tissue engineering scaffolds in vitro and in vivo. Porous membranes were fabricated by a thermally induced phase separation process of PLGA solutions in dimethylcarbonate. The parameters investigated were the PLGA concentration and the casting volume of solution. Membranes produced from 5 wt/v % polymer solutions and a 6 ml casting volume of polymer solution were selected for fabricating tubes of 3 mm diameter, 20 mm length and a nominal wall thickness of 1.5 mm. Scanning electron microscopy revealed that the structure of the tubular foams consisted of radially oriented and highly interconnected pores with a large size distribution (50-300 microm). Selected tubes were implanted subcutaneously into adult male Lewis rats. Although the lumen of the tubes collapsed within one week of implantation, histological examination of the implanted scaffolds revealed that the foam tubes were well tolerated. Cellular infiltration into the foams, consisting mainly of fibrovascular tissue, was evident after two weeks and complete within eight weeks of implantation. The polymer was still evident in the scaffolds after eight weeks of implantation. The results from this study demonstrate that the PLGA tubular foams may be useful as soft-tissue engineering scaffolds with modification holding promise for the regeneration of tissues requiring a tubular shape scaffold such as intestine.     

Radiation characteristics of a high-emissivity cylindrical-spherical cavity with obscuration

We have calculated, to first order, the apparent emissivity of the bounding diffuse surfaces of a high-emissivity cylindrical-spherical cavity enclosure. Our calculations indicate that to achieve emissivities close to a perfectly absorbing blackbody cavity along the bounding surfaces of the spherical enclosure, the radius of the sphere must be equal to or greater than a factor of 4 times the cylinder radius R(S) > or = 4R(C). Furthermore, to achieve emissivities approaching a blackbody cavity along the lower bounding surfaces of the cylindrical enclosure, the length of the cylinder must be a factor of 4 times greater than the radius of the cylinder L > or = 4R(C). In addition, we present the mathematical framework necessary to calculate radiant transfer within a cavity enclosure that contains obscuration. These results can be applied to the design of high-emissivity blackbody calibration cavities and to the reduction of stray light in terrestrial and spaceborne optical systems.     

Evolvable social agents for bacterial systems modeling

We present two approaches to the individual-based modeling (IbM) of bacterial ecologies and evolution using computational tools. The IbM approach is introduced, and its important complementary role to biosystems modeling is discussed. A fine-grained model of bacterial evolution is then presented that is based on networks of interactivity between computational objects representing genes and proteins. This is followed by a coarser grained agent-based model, which is designed to explore the evolvability of adaptive behavioral strategies in artificial bacteria represented by learning classifier systems. The structure and implementation of the two proposed individual-based bacterial models are discussed, and some results from simulation experiments are presented, illustrating their adaptive properties.