When models collide: lessons from software systems analysis

Sooner or later, the assumptions people make about what a system should do will conflict. Here's how to recognize it before it's too late. Systems analysis is rapidly coming of age. Many projects have successfully used a new approach called MBASE (Model-Based System Architecting and Software Engineering). The MBASE approach integrates the four common development models (success, product, process, and property) around the creation and use of a software architecture package. As analysts explicitly integrate models using MBASE, they can recognize and reconcile model clashes as a matter of course, instead of after the fact     

Inkjet Printing of Amphotericin B onto Biodegradable Microneedles Using Piezoelectric Inkjet Printing

The delivery of amphotericin B, a pharmacologic agent with activity against a broad spectrum of fungi as well as against parasitic protozoa, has been complicated by the fact that amphotericin B exhibits poor solubility in aqueous solutions at physiologic pH levels. In this study, piezoelectric inkjet printing was used to modify the surfaces of Gantrez 169 BF microneedles (Ashland, Covington, KY). These amphotericin B-loaded microneedles demonstrated activity against Candida parapsilosis in a radial diffusion assay. The results of this study suggest that a combination of visible light dynamic mask microstereolithography, micromolding, and piezoelectric inkjet printing may be used to prepare amphotericin B-loaded microneedles with antifungal properties. It is envisioned that microneedles containing amphotericin B may be used for transdermal delivery of pharmacologic agents for the treatment of cutaneous fungal infections as well as cutaneous leishmaniasis.     

Field‐Switchable Broadband Polarizer Based on Reconfigurable Nanowire Assemblies

Reconfigurability is one of the most critical properties of nanophotonic systems and, consequently, methods for enabling a significant degree of functionality are highly sought after. However, dynamically responsive control in top‐down fabricated photonic structures often requires extreme conditions and yields moderate modulation capability. In sharp contrast to top‐down methods, directed self‐assembly of micro‐ and nanoparticles offers a distinct avenue for reconfigurable photonics. In the present work, gold nanowire lattices are formed via electric field directed assembly in order to take advantage of their collective optical properties. The lattices are reconfigured on‐demand between two different functional states, in the form of broadband polarizers. By selectively switching the electric field between two orthogonal electrode pairs, a maximum transmission contrast of ≈50% is observed in the near‐infrared regime. Moreover, the reconfigurable transmission spectra, which are highly dependent on the nanowire size and electric field conditions, are reversible. The demonstrated proof‐of‐concept nanowire lattice polarizer provides potential for electrically reconfigurable photonic devices such as ultra‐compact polarization components, electro‐optic switches, and on‐chip modulators.     

Continuously tunable long-wavelength MEMS-VCSEL with over 40-nm tuning range

This letter presents for the first time an electrically pumped tunable vertical-cavity surface-emitting laser (VCSEL) with a record-breaking tuning range of 40 nm at long wavelengths. The VCSEL is based on a two-chip concept. The laser peak can be tuned continuously and without mode-hopping in a wavelength range above 1.55 /spl mu/m due to a microelectromechanical movable mirror membrane. The VCSEL is single mode all over the tuning range with a 32-dB sidemode suppression ratio. The laser emits a maximum output power of 100 /spl mu/W in continuous-wave operation at room temperature. Dynamic measurements of the tuning characteristics show that the 3-dB cutoff frequency for an electrothermal wavelength modulation is about 500 Hz and the 1/e-time constant of the step response is about 1 ms.     

The utilisation of creatine and its analogues by cytosolic and mitochondrial creatine kinase

We have investigated the utilisation of four analogues of creatine by cytosolic Creatine Kinase (CK), using 31P-NMR in the porcine carotid artery, and by mitochondrial CK (Mt-CK), using oxygen consumption studies in isolated heart mitochondria and skinned fibers. Porcine carotid arteries were superfused for 12 h with Krebs-Henseleit buffer at 22 degrees C, containing 11 mM glucose as substrate, and supplemented with either 20 mM beta-guanidinopropionic acid (beta-GPA), methyl-guanidinopropionic acid (m-GPA), guanidinoacetic acid (GA) or cyclocreatine (cCr). All four analogues entered the tissue and became phosphorylated by CK as seen by 31 P-NMR, Inhibition of oxidative metabolism by 1 mM cyanide after accumulation of the phosphorylated analogue resulted in the utilisation of PCr, beta-GPA-P, GA-P and GA-P over a similar time course (approximately 2 h), despite very different kinetic properties of these analogues in vitro. cCr-P was utilised at a significantly slower rate, but was rapidly dephosphorylated in the presence of both 1 mM iodoacetate and cyanide (to inhibit both glycolysis and oxidative metabolism respectively). The technique of creatine stimulated respiration was used to investigate the phosphorylation of the analogues by Mt-CK, Isolated mitochondria were subjected to increasing [ATP], whereas skinned fibres received a similar protocol with increasing [ADP]. There was a significant stimulation of respiration by creatine and cCr in isolated mitochondria (decreased K(m) and increased Vmax vs control), but none by GA, mGPA or beta-GPA (also in skinned fibres), indicating that these latter analogues were not utilised by Mt-CK. These results demonstrate differences in the phosphorylation and dephosphorylation of creatine and its analogues by cytosolic CK and Mt-CK in vivo and in vitro.     

Mobilization and transport of naturally occurring enterococci in beach sands subject to transient infiltration of seawater

This study explores the transport of enterococci (ENT) from naturally contaminated beach sands to the groundwater table via infiltrating seawater using field, laboratory, and modeling experiments. ENT were readily mobilized and transported through the unsaturated zone during infiltration events in both the field and laboratory column experiments. Detachment mechanisms were investigated using a modified version of HYDRUS-1D. Three models for detachment kinetics were tested. Detachment kinetics that are first order with respect to the rate of change in the water content and attached surface bacterial concentrations were found to provide a best fit between predicted and observed data. From these experimental and model results we conclude that detachment mechanisms associated with the rapid increases in pore water content such as air-water interface scouring and thin film expansion are likely drivers of ENT mobilization in the investigated system. These findings suggest that through-beach transport of ENT may be an important pathway through which ENT from beach sands are transported to beach groundwater where they may be discharged to coastal waters via submarine groundwater discharge.     

Becoming happier takes both a will and a proper way: An experimental longitudinal intervention to boost well-being.

An 8-month-long experimental study examined the immediate and longer term effects of regularly practicing two assigned positive activities (expressing optimism and gratitude) on well-being. More important, this intervention allowed us to explore the impact of two metafactors that are likely to influence the success of any positive activity: whether one self-selects into the study knowing that it is about increasing happiness and whether one invests effort into the activity over time. Our results indicate that initial self-selection makes a difference, but only in the two positive activity conditions, not the control, and that continued effort also makes a difference, but, again, only in the treatment conditions. We conclude that happiness interventions are more than just placebos, but that they are most successful when participants know about, endorse, and commit to the intervention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Performance of viruses and bacteriophages for fecal source determination in a multi-laboratory,comparative study

An inter-laboratory study of the accuracy of microbial source tracking (MST) methods was conducted using challenge fecal and sewage samples that were spiked into artificial freshwater and provided as unknowns (blind test samples) to the laboratories. The results of the Source Identification Protocol Project (SIPP) are presented in a series of papers that cover 41 MST methods. This contribution details the results of the virus and bacteriophage methods targeting human fecal or sewage contamination. Human viruses used as source identifiers included adenoviruses (HAdV), enteroviruses (EV), norovirus Groups I and II (NoVI and NoVII), and polyomaviruses (HPyVs). Bacteriophages were also employed, including somatic coliphages and F-specific RNA bacteriophages (FRNAPH) as general indicators of fecal contamination. Bacteriophage methods targeting human fecal sources included genotyping of FRNAPH isolates and plaque formation on bacterial hosts Enterococcus faecium MB-55, Bacteroides HB-73 and Bacteroides GB-124. The use of small sample volumes (≤50 ml) resulted in relatively insensitive theoretical limits of detection (10–50 gene copies or plaques × 50 ml⁻¹) which, coupled with low virus concentrations in samples, resulted in high false-negative rates, low sensitivity, and low negative predictive values. On the other hand, the specificity of the human virus methods was generally close to 100% and positive predictive values were ∼40–70% with the exception of NoVs, which were not detected. The bacteriophage methods were generally much less specific toward human sewage than virus methods, although FRNAPH II genotyping was relatively successful, with 18% sensitivity and 85% specificity. While the specificity of the human virus methods engenders great confidence in a positive result, better concentration methods and larger sample volumes must be utilized for greater accuracy of negative results, i.e. the prediction that a human contamination source is absent.     

Differential prediction: A methodological artifact?

Examined 31 studies involving the validity of employment and training selection procedures for Blacks and Whites. Each pair of validity coefficients from these studies was determined to be based or not be based on each of the following desirable methodological practices: use of a total number of 50 or more for both Black and White subsamples, use of a criterion for research purposes only, and use of a predictor chosen for its potential relationship to the criterion being predicted. From these data, each study was scored for adherence to the 3 desirable practices. There was a significant relationship between the validity outcome of the studies and the methodological practices score. In addition, in studies in which some validity was obtained, those whose authors reported the study as supporting the differential validity concept received significantly lower methodological practices scores. It is concluded that reported findings of differential prediction can largely be regarded as methodological artifacts. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)