Enhanced mixture analysis of poly(ethylene glycol) using high-field asymmetric waveform ion mobility spectrometry combined with fourier transform ion cyclotron resonance mass spectrometry

The combination of high-field asymmetric waveform ion mobility spectrometry (FAIMS) with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) makes possible lower detection limits, increased sensitivity, and increased dynamic range in the analysis of poly(ethylene glycol) (PEG) samples of low molecular weight. The signal gain obtained using FAIMS depends on ion identity, with a range between 1.8x and 14x obtained for various molecular ions of PEG 600. A 1.7-fold reduction in noise is obtained using FAIMS due to the elimination of chemical noise. The improved detection performance is predominantly due to a reduction in adverse Coulomb effects as a result of ions being selectively introduced into the mass spectrometer. The high ion transmission obtained using FAIMS combined with the high sensitivity of FTICR-MS detection make possible separation of multiple gas-phase conformers of PEG molecular cations that have low abundance (less than 0.2% relative abundance) and that have not been detected previously. Mixed dications of PEG that have the same nominal mass but differ by the number polymer subunits (m/Delta m up to 25,000) can be separately introduced into the mass spectrometer using FAIMS. Interactions of the carrier gas with the metal ions that are attached to the PEG molecules appear to be the most significant factor in these FAIMS separations.     

3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies

A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institu?t fu?r Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10(-7) torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10(-10) torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.     

Accurate determination of fiber strength distributions

Tensile strengths of small‐diameter ceramic fibers are commonly obtained from measured fracture loads on individual fibers and the average cross‐sectional area of the entire fiber population. The goal of the present article is to provide a critical assessment of the consequences of using the average fiber area in the inferred strength distribution. The issues are addressed through established theorems in convolution and uncertainty propagation as well as Monte Carlo simulations. Systematic errors introduced by using the average area are well‐represented by simple analytical formulae. The formulae are couched in terms of the coefficient of variation in fiber area and the dispersion in fiber strengths, characterized by the Weibull modulus. In turn, the formulae are used to determine the true values of Weibull modulus and reference strength from their nominal values. Random uncertainties associated with a finite number of tests decay slowly with number, in accordance with an inverse root scaling. When systematic errors are conflated with random uncertainties, accurate determination of the true Weibull modulus becomes increasingly challenging, even for seemingly large numbers of strength measurements. The results are used to assess the fidelity of previously‐reported experimental results based on nominal strength data.     

Building commissioning: a golden opportunity for reducing energy costs and greenhouse gas emissions in the United States

Commissioning is arguably the single most cost-effective strategy for reducing energy, costs, and greenhouse gas emissions in buildings today. Although commissioning has earned increased recognition in recent years, it remains an enigmatic practice whose visibility severely lags its potential. The application of commissioning to new buildings ensures that they deliver or exceed the performance and energy savings promised by their design and intended operation. When applied to existing buildings, commissioning identifies deficiencies and the almost inevitable “drift” from intended performance over time, and carries out interventions to put the building back on course. More formally, commissioning is a systematic, forensic approach to quality assurance and performance risk management, rather than a technology per se. This article presents the world’s largest compilation and meta-analysis of commissioning experience and the associated literature, comprising 643 non-residential buildings, 99 million ft² of floorspace, 43 million in commissioning expenditures, and the work of 37 commissioning providers. The median normalized cost to deliver commissioning is43 million in commissioning expenditures, and the work of 37 commissioning providers. The median normalized cost to deliver commissioning is 0.30/ft² (2009 currencies) for existing buildings and2009 currencies) for existing buildings and 1.16/ft² for new construction (or 0.4% of the overall construction cost). The one third of projects for which data are available reveal over 10,000 energy-related deficiencies, the correction of which resulted in 16% median whole-building energy savings in existing buildings and 13% in new construction, with payback times of 1.1 and 4.2 years, respectively. Because energy savings exceed commissioning costs, the associated reductions in greenhouse gas emissions come at a “negative” cost of −$110/tonne CO₂ for new buildings and −$110/tonne CO₂ for new buildings and −25/tonne for new construction. Cases with comprehensive commissioning attained nearly twice the overall median level of savings and five times the savings of the least-thorough projects. Significant non-energy benefits such as improved indoor air quality are also achieved. Applying the median whole-building energy-saving values to the US non-residential buildings stock corresponds to an annual energy-saving potential of $30 billion (and 340 Mt of CO₂) by the year 2030.     

Model-based control of titer and glycosylation in fed-batch mAb production: Modeling and control system development

Therapeutic monoclonal antibodies (mAbs) are typically manufactured using mammalian cell cultures in fed-batch bioreactors, with increasing emphasis on meeting productivity and product quality attribute targets that depend strongly on such process variables as nutrient feed rates and bioreactor operating conditions. In this article, we identify, categorize, and address the challenges of achieving both productivity and product quality goals simultaneously, by developing a multivariable, model-based control system that can satisfy multiple production objectives in a fed-batch cell culture process. Here, we discuss model development and present theoretical concepts of observability and controllability that are essential to understanding and handling effectively these intrinsic challenges. Subsequently, we evaluate via simulation the performance of the outer-loop model predictive control and demonstrate the overall capability to satisfy complex production objectives in a laboratory scale bioreactor, as a first step toward the ultimate goal of creating an advanced control system for fed-batch mAb manufacturing processes.     

Temperature Distribution in Fluidized Beds of Porous Particles with Liquid Injection

Liquid injection in fluidized beds is used to add reactants or to improve the heat management in the reactor. This injection will increase the complexity of reactor due to the formation of agglomerates. In this work the effect of the injection on the particle temperature distribution in a fluidized bed of porous particles is determined experimentally using particle image velocimetry and infra-red thermography. The main property of the porous particles influencing the distribution is the specific surface area. In addition, the porosity has a large effect on the defluidization of the fluidized bed.     

Regulating Zinc Nucleation Sites and Electric Field Distribution to Achieve High-Performance Zinc Metal Anode via Surface Texturing

Understanding zinc (Zn) deposition behavior and improving Zn stripping and plating reversibility are significant in developing practical aqueous Zn ion batteries (AZIBs). Zn metal is abundant, cost-effective, and intrinsically safe compared with Li. However, their similar inhomogeneous growth regime harms their practicality. This work reports a facile, easily scalable, but effective method to develop a textured Zn with unidirectional scratches on the surface that electrochemically achieves a high accumulated areal capacity of 5530 mAh cm⁻² with homogenized Zn deposition. In symmetric cells, textured Zn presents a stable cycling performance of 1100 hours (vs 250 h of bare Zn) at 0.5 mA cm⁻² for 0.5 mAh cm⁻² and lower nucleation and plating overpotentials of 120.5 and 41.8 mV. In situ optical microscopy and COMSOL simulation disclose that the textured surface topography can 1) homogenize the electron field distribution on the Zn surface and regulate Zn nucleation and growth, and 2) provides physical space to accommodate Zn deposits, prevent the detachment of “dead” Zn, and improve the structural sufficiency of Zn anode. Moreover, differential electrochemical mass spectrometry analysis find that the textured Zn with regulated interfacial electron activity also presents a higher resistance toward hydrogen evolution and other parasitic reactions.     

An improved correlation for dry pressure losses across static mixers at high Reynolds numbers

Corrugated (SMV-style) static mixers are industrially important for process intensification and can promote gas–liquid mass transfer in processes such as sour gas sweetening. Current correlations for pressure loss are limited to Reynolds numbers (Re) below 40 000, far below the ranges encountered in natural gas systems (10⁵ < Re < 10⁷). An experimental and numerical study of pressure drop across multiple corrugated mixers in the range of 10⁴ < Re <2 × 10⁵ encompassing different configurations (aligned, rotated), pipe diameters (1–4 in.), and sand grain surface roughness values (10–5000 μm) is reported here. Our previous correlation for pressure loss across a single corrugated element is shown to be extendable to multiple corrugated mixing elements. Through the inclusion of mixer tortuosity (τ), porosity (ε), and macro-scale (geometric) wall roughness (e), the correlation also matches historical pressure drop data (at different τ, ε) reported in literature, thereby demonstrating the utility of these variables as parameters that can help optimize mixer performance. Experiments and computational fluid dynamics (CFD) modelling revealed that the rotated configuration increased the residence time by up to 13% in comparison to the aligned configuration. This may have implications on the selective absorption of sour gas components that are based on fast kinetics. In addition, the role of wall roughness (both pipe housing and mixer) was demonstrated to be significant in this study (accounting for 55% of the pressure losses) and must be accurately accounted for when scaling laboratory measurements.     

Structure-Property Relationships Governing Membrane-Penetrating Behaviour of Complex Coacervates

Complex coacervates are phase-separated liquid droplets composed of oppositely charged multivalent molecules. The unique material properties of the complex coacervate interior favours the sequestration of biomolecules and facilitates reactions. Recently, it is shown that coacervates can be used for direct cytosolic delivery of sequestered biomolecules in living cells. Here, it is studied that the physical properties required for complex coacervates composed of oligo-arginine and RNA to cross phospholipid bilayers and enter liposomes penetration depends on two main parameters: the difference in ζ-potential between the complex coacervates and the liposomes, and the partitioning coefficient (K_p) of lipids into the complex coacervates. Following these guidelines, a range of complex coacervates is found that is able to penetrate the membrane of living cells, thus paving the way for further development of coacervates as delivery vehicles of therapeutic agents.