Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R² = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R² = 0.95), rather than the strongly attached biofilm (R² = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry     

Natural convection of liquid metal in a vertical annulus with lateral and volumetric heating in the presence of a horizontal magnetic field

MHD free convection of a liquid metal is studied in a closed vertical annulus in which the upper and bottom walls are adiabatic while the cylindrical walls are kept at different temperatures. The flow is driven by two mechanisms; the temperature difference between the two cylindrical walls and the volumetric heating. A constant horizontal magnetic field is also imposed resisting the fluid motion. The laminar and turbulent regimes of the flow are assessed by performing three-dimensional direct numerical simulations. The results show that in the absence of the magnetic field, turbulent flow is developed in most of the cases, while as the magnetic field increases the flow becomes laminar. The highest temperature is found in the upper-central part of the annular cavity when the fluid is heated volumetrically, resulting in the creation of two convection currents as the hot fluid ascends in the central part and descends close to both colder walls. The Hartmann and Roberts layers developing near the walls normal and parallel to the magnetic field, respectively, are found to be responsible for the loss of axisymmetry of the present flow.     

Paclitaxel plus high-dose cyclophosphamide with G-CSF support in patients with relapsed and refractory aggressive non-Hodgkin's lymphoma

Based on the single-agent activity of both paclitaxel and cyclophosphamide in the treatment of non-Hodgkin's lymphoma (NHL), we conducted a phase II study to evaluate the efficacy of the combination of the two drugs in patients with refractory and relapsed aggressive NHL. All patients received 900 mg/m2 bolus of cyclophosphamide intravenously daily for 3 consecutive days with a concurrent infusion of 150 mg/m2 of paclitaxel over 72 h (50 mg/m2/d). 24 h after the completion of chemotherapy, patients received subcutaneous injections of 5 microg/kg of granulocyte-colony stimulating factor (G-CSF) daily until white cell count recovery. Treatment was repeated every 3 weeks. Patients who had at least a partial response (PR) after two courses continued to receive a maximum of four courses. Patients with responding disease were allowed to undergo high-dose chemotherapy followed by stem-cell/bone marrow transplantation if they were eligible. Of the 77 patients who were eligible for the study, 74 (96%) were evaluable for toxicity and treatment response. The overall response rate was 45% (95% CI 33-57%). Patients who received treatment after their disease relapsed from a complete response (CR) had an 81% response rate (38% CRs), whereas those with primary refractory disease had a 22% response rate. Toxicities of > grade 2 included alopecia (100%) and stomatitis (25%). Neutropenic fever of grade > 2 occurred after 18% of the courses, and platelet count of < or = 20 x 10(9)/l developed after 20% of the courses. Thus, the combination of paclitaxel plus high-dose cyclophosphamide is an effective new regimen in the treatment of refractory and relapsed NHL.     

Modeling the Terminal Response of a Bundle of Twisted-Wire Pairs Excited by a Plane Wave

The proposal to use multiple-input multiple-output vectored transmission in digital subscriber line (DSL) systems has prompted a revision of the channel noise models used to characterize twisted-wire pairs (TWPs). In this context, a transmission-line model for predicting the terminal response of a bundle of TWPs to an illuminating plane-wave electromagnetic field is introduced. The corresponding nonuniform transmission-line equations for the multiconductor system are solved numerically. The goal of the model is to provide a tool for solving a wide variety of radio-frequency interference problems in DSL systems. Computed results for a variety of TWP structures are presented, and the issue of small random twisting nonuniformities is explored.     

MCP-1, not MIP-1alpha, is the endogenous chemokine that cooperates with TGF-beta to inhibit the cycling of primitive normal but not leukemic (CML) progenitors in long-term human marrow cultures

The long-term culture (LTC) system has been useful for analyzing mechanisms by which stromal cells regulate the proliferative activity of primitive normal, but not chronic myeloid leukemia (CML), hematopoietic progenitor cells. In previous studies, we identified two endogenous inhibitors in this system. One is transforming growth factor-beta (TGF-beta), which is equally active on primitive normal and CML progenitors. The other we now show to be monocyte chemoattractant protein-1 (MCP-1). Thus, MCP-1, when added to LTC, blocked the activation of primitive normal progenitors but did not arrest the cycling of primitive CML progenitors. Moreover, the endogenous inhibitory activity of LTC stromal layers could be overcome by the addition of neutralizing antibodies to MCP-1, but not to macrophage inflammatory protein-1alpha (MIP-1alpha). However, neither of these antibodies antagonized the inhibitory activity of NAc-Ser-Asp-Lys-Pro (AcSDKP) on primitive normal but not CML progenitor cycling in this system. Moreover, none of six other -C-C- or -C-X-C- chemokines, previously shown to inhibit primitive normal human CFC proliferation in semisolid assays, were found to act as negative regulators when added to normal LTC. These results provide further support for the concept that primitive CML progenitor cell proliferation is deregulated when these cells are exposed to limiting concentrations of multiple inhibitors, only some of which have differential actions on normal and Ph+/BCR-ABL+ cells.     

A 10-Bit,Low Power,Successive Approximation,Digitally Auto-Zeroed CMOS ADC Core for the NASA TRIO Smart Sensor System on a Chip

In spacecraft applications there is a great need for robust analogue to digital converters (ADC) that can withstand the harsh space environment. Commercially available ADCs cannot operate in the space environment due to radiation effects. In this paper we present an ADC that has been developed for the NASA TRIO smart sensor system on a chip (SoC), a versatile low power device specifically designed for spacecraft data acquisition and telemetry of several types of sensors such as temperature, voltage/current transducers, radFETs, etc. It is required for the ADC to operate in excess of 300 Krad total ionizing dose and to be robust to single event upsets. The successive approximation topology was chosen and it was enhanced with a special auto-zeroing technique to compensate for possible lifetime offset errors. Due to the comparator design, a rail-to-rail input capability is achieved, a feature very useful in some type of Vdd ratio metric sensors. It has 10-bit resolution for a reference in the range 0.1 to Vdd + 1 V, and for power supply in the range 2.5 to 5.5 V; the positive reference terminal V_ref+ is settable up to Vdd + 0.5 V and the negative voltage terminal is settable down to GND-0.5 V. The power dissipation is less than 2 mW at 50 Ksamlles/sec. The TRIO chip is used in several NASA spacecraft including CONTOUR, STEREO, MESSENGER, EUROPA, PLUTO, etc.George Kottaras was born in Athens, Greece in 1974. He received the Diploma degree (five years with thesis) in Electrical Engineering from Democritos University of Thrace, Greece in 1996. He is currently pursuing the Ph.D. degree on Scientific Space Instruments and spacecraft avionics at Space Research Laboratory, DUTh. He has specialized in VLSI technologies at JHU/APL for about five years.His research interests include mixed signal analog/digital design, ADCs, design for testability, testing, smart sensors and data acquisition.Nikolaos P. Paschalidis was born is Serres, Greece in 1963. He received the Diploma and Ph.D. degrees in Electrical Engineering from the Democritus University of Thrace (DUTh), Greece, in 1985 and 1992 respectively. He has been in appointment with the Johns Hopkins University, since 1989, where his research specialized in advanced microelectronics, space instrumentation, and space physics.He later joined the Space Department of JHU Applied Physics Laboratory (JHU/APL) Laurel, MD, as a postdoctoral fellow and presently he is Principal Staff. His research interests are in analog and mixed signal microelectronics, microsensors, microsystems and their applications in in-situ and remote sensing spacecraft instruments and avionics. He pioneered in the Advanced Technology Development program of NASA for smaller better faster missions by leading efforts in the circuit level of: amplifiers, comparators, voltage references, ADC and DAC, PLLs, TDCs, SEU and radiation tolerant design, physical design, design for testability, testing and space qualification; in the system on a chip level flight ready chips including: the Time of Flight chip for precise time pickoff and time digitization, Energy chip for radiation energy measurement, the TRIO smart sensor chip for spacecraft data acquisition and control etc; in the instrument and spacecraft level: application of these technologies in particle and plasma spectrometers, laser altimeters, photon/particle imagers, TOF mass spectrometers, X-ray and gamma-ray instruments, spacecraft avionics. Space missions using these technologies include: Cassini, Image, Contour, Messenger, Pluto, Mars missions, etc. Dr. Paschalidis published extensively in microelectronics, space instrumentation, and space physics. He supervises research of graduate students in ECE and Applied Physics. He supervised DUTh graduate students at JHU/APL for many years. He participates as principal investigator and co-investigator in several space programs; he participates in communities with space related activities including: the IEEE Aerospace, Nuclear Sciences, NASA VLSI, IAA, and American Geophysical Union.Emmanuel T. Sarris was bom in Athens, Greece, in 1945. He received the physics degree from the University of Athens in 1967 and the Ph.D. degree in space physics from the University of Iowa, Iowa City, in 1973.He was a Postdoctoral Fellow in the Applied Physics Laboratory, The Johns Hopkins University, Baltimore, MD, from 1974 to 1976. From 1976 to 1977, he was a Research Scientist at the Max-Planck-Institut. He has been a Professor of Electrodynamics, Department of Electrical Engineering, University of Thrace, Greece, and Director of the Laboratory of Electrodynamics and Space Research since 1977. He was the Director of the Institute of Ionospheric and Space Physics, National Observatory of Athens from 1990 to 1996. His research interests include space plasma electrodynamics, design, construction, and testing of space instrumentation, satellite communications, satellite remote sensing. He is coinvestigator in the international space missions: Ulysses, Geotail, Interball, Cluster. He is the author of 270 refereed publications and 300 presentations at international meetings. Dr. Sarris is a member of the COSPAR Council. He was elected Johns Hopkins Scholar Award in 1992 and received the Award for Academic Excellence in 1994.Nikos Stamatopoulos was born in Peloponnisos, Greece in 1969. He received the diploma degree (five years with thesis) of Electrical Engineering from Democritos University of Thrace, Greece in 1994. He is currently pursuing the Ph.D. degree on Scientific Space Instruments at Space Research Laboratory, DUTh. He has specialized in VLSI technologies with emphasis in low noise analog design at JHU/APL for about five years.His main research interests are on Analogue CMOS VLSI design for fast time acquisition.Kostas Karadamoglou was born in Macedonia, Greece, in 1970. He received the diploma degree (five years with thesis) of Electrical Engineering from Democritos University of Thrace, Greece in 1994. He is currently pursuing the Ph.D. degree on Scientific Space Instruments at Space Research Laboratory, DUTh. He has specialized in VLSI technologies with emphasis in high-speed digital design at JHU/APL for about five years.His main research interests are on the design of application specific Time to Digital Converters.Vassilis Paschalidis was born in Serres, Greece in 1964. He received the B.S. degree in Electrical Engineering from the Technological Institute of Kabala, Greece in 1988. He worked n the industry for electronic automation. He has specialized in VLSI technologies at JHU/APL for about five years with emphasis in physical design. His research interests include mixed signal analog/digital VLSI design.     

Antibacterial Activity of Copper Nanoparticles against Xanthomonas campestris pv. vesicatoria in Tomato Plants

Copper-based bactericides have appeared as a new tool in crop protection and offer an effective solution to combat bacterial resistance. In this work, two copper nanoparticle products that were previously synthesized and evaluated against major bacterial and fungal pathogens were tested on their ability to control the bacterial spot disease of tomato. Growth of Xanthomonas campestris pv. vesicatoria, the causal agent of the disease, was significantly suppressed by both nanoparticles, which had superior function compared to conventional commercial formulations of copper. X-ray fluorescence spectrometry measurements in tomato leaves revealed that bioavailability of copper is superior in the case of nanoparticles compared to conventional formulations and is dependent on synthesis rather than size. This is the first report correlating bioavailability of copper to nanoparticle efficacy.     

Laminar Free Convection in a Square Enclosure Driven by the Lorentz Force

A numerical study is presented of laminar free convection flow driven by magnetic forces. An external magnetic field with one spatially varying component is applied to an electrically conducting fluid in a square enclosure. This magnetically-driven flow is controlled by the intensity and the wave number of the applied magnetic forcing. In addition, when the enclosure is heated laterally in a non-zero gravity environment, the resulting buoyant forces may contribute or resist the magnetically-driven fluid motion. The present results show that a strong magnetic field can even reverse the buoyant flow. The circulation intensity of the flow and the heat transfer from the sidewalls is increased with increasing magnetic field or with decreasing magnetic Reynolds number. The wave number of the magnetic forcing is also an important parameter that determines the vortex patterns and, consequently, the convection heat transfer.     

The influence of the cohesive process zone in hydraulic fracturing modelling

This paper studies the importance of the cohesive zone in the modelling of a fluid driven fracture under plain strain conditions. The fracture is driven by pumping of an incompressible viscous fluid at the fracture inlet. Rock deformation is modeled for linear elastic and poroelastic solids. Fluid flow in the fracture is modeled by lubrication theory. The cohesive zone approach is used as the fracture propagation criterion. Finite element analysis was used to compute the solution for the crack length, the fracture opening and propagation pressure as a function of the time and distance from the wellbore. It is demonstrated that the crack profiles and the propagation pressures are larger in the case of elastic-softening cohesive model compared to the results of the rigid-softening cohesive model for both elastic and poroelastic cohesive solids. It is found that the results are affected by the slope of the loading branch of the cohesive model and they are nearly unaffected from the exact form of the softening branch. Furthermore, the size of the process zone, the fracture geometry and the propagation pressure increase with increasing confining stresses. These results may explain partially the discrepancies in net-pressures between field measurements and conventional model predictions.