Temperature Modulation Measurements of the Thermal Properties of Nanosystems at Low Temperatures

We report on the dynamic measurements of thermal properties of nanosystems at very low temperatures. These techniques are based on the modulation of the temperature and hence leads to highly sensitive measurements. We will discuss the intrinsic limitations of these methods when the thermal properties of nano-objects are studied at very low temperatures, much below 1 K. Firstly, we will present thermal conductance measurements using the 3ω method. This technique is limited at low temperatures due to the significant increase of the mean free path. Secondly, heat capacity measurements using ac calorimetry are outlined, and again restrictions occur due to the continuous temperature gradient inherent to that technique. Propositions are made in order to overcome these limitations.     

Jacobian calculation using the multidimensional fast Fouriertransform in the harmonic balance analysis of nonlinear circuits

A technique which allows the gradient of frequency-domain simulation variables to be analytically determined using time-domain derivative information and the multidimensional fast Fourier transform is discussed. It is shown that this technique can be efficiently implemented when a circuit is driven by any number of incommensurate input frequencies. A harmonic balance simulator that uses this technique to determine the entries of the Jacobian matrix needed in a quasi-Newton iteration scheme is constructed. A significant reduction of simulation time is observed when compared with a harmonic balance simulator that uses transforms based on matrix multiplication     

USER PRODUCTIVITY AND WINDOWS

Many of today's and tomorrow's applications require the increased performance of a multiple windows terminal. There are four choices for IS managers who want to advise their operations or administrative staff on a multiple windows capability. This article compares and contrasts the options to help IS managers choose among them and meet the goal of increasing the productivity of business users.     

Culturally competent interventions for abused and suicidal African American women.

This article focuses on interventions with low-income, African American women who are survivors of domestic abuse and who have made one or more suicide attempts. The authors review the literature on domestic abuse and suicidal behavior in African American women, and discuss the association between abuse and suicide in this population. Next, they propose an integrated theoretical model for understanding suicidal behavior as one possible coping response to the stress of a domestic abuse situation. The model utilizes concepts from the literature on stress and coping as well as stages of change. A culturally sensitive group treatment intervention that is based on the theoretical model is presented. The intervention focuses on ensuring women's safety, increasing coping skills and resource mobilization, and promoting supportive relationships in a manner that is consistent with each woman's sociocultural context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Surface acoustic wave nebulization facilitating lipid mass spectrometric analysis

Surface acoustic wave nebulization (SAWN) is a novel method to transfer nonvolatile analytes directly from the aqueous phase to the gas phase for mass spectrometric analysis. The lower ion energetics of SAWN and its planar nature make it appealing for analytically challenging lipid samples. This challenge is a result of their amphipathic nature, labile nature, and tendency to form aggregates, which readily precipitate clogging capillaries used for electrospray ionization (ESI). Here, we report the use of SAWN to characterize the complex glycolipid, lipid A, which serves as the membrane anchor component of lipopolysaccharide (LPS) and has a pronounced tendency to clog nano-ESI capillaries. We also show that unlike ESI SAWN is capable of ionizing labile phospholipids without fragmentation. Lastly, we compare the ease of use of SAWN to the more conventional infusion-based ESI methods and demonstrate the ability to generate higher order tandem mass spectral data of lipid A for automated structure assignment using our previously reported hierarchical tandem mass spectrometry (HiTMS) algorithm. The ease of generating SAWN-MS(n) data combined with HiTMS interpretation offers the potential for high throughput lipid A structure analysis.     

Novel “Vibrating Wire Like” NEMS and MEMS Structures for Low Temperature Physics

Using microfabrication techniques, it has become possible to make mechanical devices with dimensions in the micro and even in the nano scale domain. Allied to low temperature techniques, these systems have opened a new path in physics with the ultimate goal of reaching the quantum nature of a macroscopic mechanical degree of freedom (LaHaye et al. in Science 304:74, 2004). Within this field, materials research plays a significant role. It ranges from the fundamental nature of the dissipation mechanisms at the lowest temperatures, to the non-linear behavior of mechanical oscillators. We present experimental results on cantilever structures mimicking the well known “vibrating wire” technique, which present many advantages as far as the mechanical studies are concerned: the measurement is phase-resolved, they can be magnetomotive and electrostatically driven, and support extremely large displacements. Moreover, these devices can be advantageously used to study quantum fluids, making the link with conventional low temperature physics.     

Formation of droplet networks that function in aqueous environments

Aqueous droplets in oil that are coated with lipid monolayers and joined through interface bilayers are useful for biophysical measurements on membrane proteins. Functional networks of droplets that can act as light sensors, batteries and electrical components can also be made by incorporating pumps, channels and pores into the bilayers. These networks of droplets mimic simple tissues, but so far have not been used in physiological environments because they have been constrained to a bulk oil phase. Here, we form structures called multisomes in which networks of aqueous droplets with defined compositions are encapsulated within small drops of oil in water. The encapsulated droplets adhere to one another and to the surface of the oil drop to form interface bilayers that allow them to communicate with each other and with the surrounding aqueous environment through membrane pores. The contents in the droplets can be released by changing the pH or temperature of the surrounding solution. The multicompartment framework of multisomes mimics a tissue and has potential applications in synthetic biology and medicine.     

Redox processes and release of organic matter after thermal treatment of a TCE-contaminated aquifer

Redox conditions in heated and unheated microcosm experiments were studied to evaluate the effect of thermal remediation treatment on biogeochemical processes in subsurface environments. The results were compared to field-scale observations from thermal treatments of contaminated sites. Trichloroethene-contaminated aquifer material and groundwater from Ft. Lewis, WA were incubated for 200 days at ambient temperature (i.e., 10 degrees C) or heated to 100 degrees C for 10 days and cooled slowly over a period of 150 days to mimic a thermal treatment. Increases of up to 14 mM dissolved organic carbon were observed in the aqueous phase after heating. Redox conditions did generally not change during heating in the laboratory experiment, and only minor changes occurred as an effect of heat treatment in the field. The conditions were slightly manganese/iron-reducing in two sediments and possibly sulfate-reducing in the third sediment based on production of up to 0.20 mM dissolved iron and 0.15 mM dissolved manganese and consumption of 0.08 mM sulfate. The calculated energy gain of less than -20 kJ/mol H2 for iron and sulfate reduction as well as methane production indicated that these processes were thermodynamically favorable. Sulfate reduction and methane production occurred in the unheated microcosms upon lactate amendment. Little or no reduction of the redox level was identified in heated lactate-amended microcosms, possibly because of limited microbial activity. Because the redox conditions, pH, and alkalinity remained within normal aquifer levels upon heating, bioaugmentation may be feasible for stimulating anaerobic dechlorination in heated samples or in future field applications.