Kenneth A. Strom

Retention and clearance of inhaled submicron carbon black particles

Carbon black aerosols were used as a probe of the pulmonary retention and clearance of submicron particles. Male Fischer rats (COBS CD) were exposed for 20 h/d, 7 d/wk for 1, 3, or 6 wk to either 7 +/- 2 mg/m3 carbon black or filtered air. The submicron aerosol (mass median aerodynamic diameter, MMAD, 0.24 microns) was generated with a Wright dust feed-cyclone system. Lung and hilar lymph node particle burdens were determined immediately following the exposure and at preselected intervals up to 1 yr postexposure. After 1-, 3-, and 6-wk exposures, the lung burdens were 1.1 +/- 0.1, 3.5 +/- 0.2, and 5.9 +/- 0.1 mg, respectively. One year after a 1-, 3-, or 6-wk exposure, 8%, 46%, and 61% of the initial lung burden remained in the lungs. Initially, the hilar lymph nodes contained 0.2%, 0.9%, and 2.0% of the lung burdens in the 3 exposure groups, respectively. At 1 yr postexposure, particle translocation from the lungs led to a rise in lymph node burdens to 1%, 21%, and 27% of the initial lung burden. The retention of carbon black in both the lungs and lymph nodes combined was 9%, 67%, and 89% for the 1-, 3-, and 6-wk exposed animals. Lung clearance was modeled as a compartmental system consisting of four lung compartments and a regional lymph node compartment. The results from the model are similar for carbon black and diesel engine exhaust particles. However, the compartmental kinetics of carbon black differed in two ways: the deposition efficiency in the alveolar region was lower than that for diesel exhaust particles, and there was earlier transport of particles to the regional lymph nodes. These results showed that when lung burdens reached 0.8 mg, lung clearance was decreased by 50% and lymphatic transport of insoluble particles was increased.

Response of pulmonary cellular defenses to the inhalation of high concentrations of diesel exhaust

Rats were exposed to three concentrations of diluted diesel exhaust for 6 mo and 1 yr. Bronchopulmonary lavage was used to obtain the pulmonary phagocytes from the animals in order to study the response of the phagocytic defenses to the inhaled particulate. The cell numbers and volumes were measured using an electronic particle counter. The cell counts of alveolar macrophages (AM) were proportional to the concentration of diesel exhaust particulate (DP) in the chronic exposures. AM increased in the lungs in response to the rate of DP mass entering the lungs, rather than to the total DP burden in the lung. The geometric mean volumes of AM from the exposed and control animals were approximately 1100 micron3 at both 6 and 12 mo of exposure, although exposed cell-volume distributions skewed towards larger sizes. The AM volume distributions extended to 2000 micron3 in both control and 250 micrograms DP/m3 exposed animals and up to 5000 micron3 in cells from animals exposed to 750 and 1500 micrograms DP/m3. The volume distributions were found to be reproducible in equivalent control and exposed cell populations. Polymorphonuclear leukocytes were present in the lavaged cell populations from the animals exposed to 750 and 1500 micrograms/m3. In addition, at 1 yr of exposure, lymphocytes were also lavaged from animals exposed to 750 and 1500 micrograms DP/m3. Protein, beta-glucuronidase activity, and acid phosphatase activity were measured in the lavaged cells, and were elevated in the cells from animals exposed to 750 and 1500 micrograms/m3. The buoyant density of diesel-laden AM was found to be greater than that of control AM, and overlapped with the buoyant density of the polymorphonuclear leukocytes.

Pulmonary phospholipidosis in rats respiring air containing diesel particulates

Rats chronically exposed to diesel particulates (dp) or given intratracheally a single dose of dp show increased levels of phospholipids in the lungs and in pulmonary lavage fluid. Pulmonary phospholipidosis is accompanied by increased lecithin levels and by increased palmitate content in lecithin of both lungs and pulmonary lavage fluid. A de novo increase of pulmonary and hepatic phospholipid (PL) formation was detected 5 days after rats were treated with dp. We hypothesize that a dp-stressed lung releases a pulmonary lipogenic factor (PLF), which stimulates hepatic lipogenesis. This was further tested by an in vitro study in which primary cultures of free hepatocytes were incubated with [2-14C]acetate and various molecular weight fractions of a pulmonary homogenate from rats. The results from these studies indicated that in rat lung homogenates a PLF exists of greater than 100,000 Da molecular mass. The results also indicate that respired air containing a dp concentration of greater than 750 micrograms dp/m3 of air would result in a mild phospholipidosis in the lung, whereas a dp dose in respired air of 250 micrograms dp/m3 of air for 2 years did not alter pulmonary PL content in rats.

Inhaled particle retention in rats receiving low exposures of diesel exhaust

To study the effects of a low concentration exposure on the retention and clearance of submicron particles from the lungs, we exposed male Fisher 344 rats to diesel exhaust diluted to 50 micrograms diesel exhaust particles (DP)/m3, 20 h/d, 7 d/wk for 52 wk. Lung burdens (amount of DP in lungs) and the alveolar macrophage burdens were measured up to 52 wk postexposure. By 1 yr postexposure at least 80% of the DP was eliminated from the lungs and similarly cleared from the lavaged pool of macrophages. The DP remaining in the lungs was observed in alveolar, parabronchial and paravascular maculae. In contrast to previous high concentration exposure studies, only trace amounts of particles were observed in the mediastinal lymph nodes. To study the concentration dependence of particle retention, rats were exposed to equivalent exposures of 18 d x mg DP/m3 delivered at 5700 micrograms/m3 for 3 d, 1600 micrograms/m3 for 12 d, 250 micrograms/m3 for 72 d, or 50 micrograms/m3 for 365 d. Higher lung and macrophage burdens were initially achieved with the brief, high concentration exposures. During the postexposure period, animals exposed to the higher concentrations cleared more of the lung burden. Exposure to lower concentrations resulted in higher long-term lung burdens. These results are consistent with a model of lung clearance in which the macrophage burden and the duration of exposure are both important to the formation of the maculae. In a brief high concentration exposure, the macrophage burden rises rapidly, but then declines rapidly. However, in longer low concentration exposures, the macrophage burden will not reach the same peak, but stays at intermediate levels during the exposure and stimulates a steady development of the lung maculae from particle-laden macrophages leaving the active pool of pulmonary phagocytes.

Lymphatic transport of inhaled diesel particles in the lungs of rats and guinea pigs exposed to diluted diesel exhaust

Factors influencing the disposition of the inhaled diesel particles were studied by analyzing the deposition of radioactively labelled diesel particles in the respiratory system, by determining the specific function of alveolar cellular mechanisms in the primary defense against inhaled particles and by identifying the important role of the lymphatic system in the lung clearance of experimental animals exposed to diluted emissions from a diesel engine. Radioactive 131Barium was used as a tracer of diesel particles and the deposition efficiency was determined to be 15%±6% of the inhaled dose in the Fischer 344 rat strain. The number of cells obtained by bronchial lavage increased significantly after a prolonged exposure to a concentration of 1500 μg/m3 of diesel particles. The increased cell number was more than twofold, contained two distinct cell populations (alveolar macrophages and neutrophils) and represented a reactive mobilization of the defense mechanisms in the organism. Light microscopy studies investigated the role of lymphatic transport of the particulate matter and revealed that the peribrochial and perivascular aggregates of lymphoid tissue contained diesel particles even after short exposure periods at low dose levels. With the increasing burden of particles in the respiratory system, the coloration of hilar and mediastinal lymph nodes continuously changed to gray and finally to dark black, depending upon the dose level and exposure. However, at all exposure levels, most of the diesel particles in the alveoli were phagocytized by an increased alveolar cellular defence and particle-containing macrophages were actively moving towards the mucociliary escalator or towards lymphatic channels leading to peribronchial lymphoid aggregates and bronchial or mediastinal lymph nodes. In the lymph nodes, alveolar macrophages containing diesel particles were found mostly in the afferent subcapsular lymphatic vessels and marginal sinuses. In the later stages, cellular structure disintegrated and large aggregates of particulate matter were dispersed throughout the medullary cords with increasing accumulation towards the hilus. It is concluded that the lymphoid aggregates and lymphatic nodes play an important role in sequestering diesel particles or particle-containing phagocytizing cells and provide a pathway, in addition to the mocociliary clearance for particulate removal from the deep pulmonary region.

The design and experimental validation of an ultrafast shape memory alloy resettable (SMART) latch

Latches are essential machine elements utilized by all sectors (military, automotive, consumer, manufacturing, etc.) with a growing need for active capabilities such as automatic release and reset, which require actuation. Shape memory alloy (SMA) actuation is an attractive alternative technology to conventional actuation (electrical, hydraulic, etc.) because SMA, particularly in the wire form, is simple, inexpensive, lightweight, and compact. This paper introduces a fundamental latch technology, referred to as the T-latch, which is driven by an ultrafast SMA wire actuator that employs a novel spool-packaged architecture to produce the necessary rotary release motion within a compact footprint. The T-latch technology can engage passively, maintain a strong structural connection in multiple degrees of freedom with zero power consumption, actively release within a very short timeframe (<20 ms, utilizing the SMA spooled actuator), and then repeat operation with automatic reset. The generic architecture of the T-latch and governing operational behavioral models discussed within this paper provide the background for synthesizing basic active latches across a broad range of applications. To illustrate the utility and general operation of the T-latch, a proof of concept prototype was designed, built, and experimentally characterized regarding the basic functions of engagement, retention, release, and reset for a common case study of automotive panel lockdown. Based on the successful demonstration and model validation presented in this study, the T-latch demonstrates its promise as an attractive alternative technology to conventional technologies with the potential to enable simple, low-cost, lightweight, and compact active latches across a broad range of industrial applications.

Experimental investigation of active adaptability of the SMArt (SMA reseTtable) dual-chamber pneumatic lift device for pedestrian protection

The rapid urbanization of the world has led to an increase in pedestrian involvement in automotive crashes, prompting some countries to establish pedestrian regulations. A promising approach to address pedestrian safety is the use of active lift devices to raise the hood upon detection of a pedestrian impact, thereby increasing the crush distance between the hood and vehicle hard points (i.e. engine). Current systems are generally not reusable or resettable and lack extrinsic effect compensation. The dual chamber SMArt (SMA ReseTtable) lift system presented in this paper is a fully automatically resettable system utilizing a stored energy approach with a pneumatic cylinder and a two stage ultrafast shape memory alloy (SMA) actuated valve. This active lift possesses the unique functionality to tailor lift performance and compensate for extrinsic effects such as changes in temperature, mass, and platform using cylinder pressure and exhaust valve opening timing profile as operating parameters. As a proof of concept, a dual chamber SMArt lift system was designed, fabricated, and installed in a vehicle hood bay testbed. Full cycle tests demonstrated the functions of lift, lower and reset within the proper timing. The effect of additional mass, was experimentally characterized and two insitu device parameters, pressure and valve profile, were investigated as means to mitigate these extrinsic effects. This experimental study indicates that the dual chamber SMArt lift device may be a feasible alternative for pedestrian protection with automatic reset/reusability along with capability to adapt in-situ to maintain performance within a narrow timing window by compensating for extrinsic effects.

Feasibility study of the dual-chamber SMART (SMA ReseTtable) lift device

Pedestrian protection is a major focus of automotive crashworthiness with new regulations taking effect worldwide. While there are many approaches to reducing the head-injury-criteria (HIC), a leading approach is to actively lift the hood to increase the crush distance to rigid underhood components. Most current lift devices are single-use, requiring the hood to be manually returned to a drivable position, and may damage the hood during lift due to inappropriate lift rates. This paper addresses these issues with an alternative approach using stored energy marrying conventional (pneumatic) and smart materials (Shape Memory Alloy) actuation. The SMART (SMA ReseTtable) hood lift device comprises a dual chamber cylinder which releases stored pneumatic energy via an ultra-fast SMA exhaust valve, raising a piston attached to the hood. The device can be automatically reset and rearmed through pressurization of the chambers and the energy dissipated for service by evacuating both chambers. This approach is unique in that several design parameters such as pressure and valve opening/timing profile can be altered in the field to compensate for temperature, added mass (such as snow) or platform changes. This paper presents the concept of this device and the parametric design of the pneumatic cylinder and valve orifice based on an analytical performance model. Two valve concepts are presented: direct and indirect, where the direct valve is simpler and more controllable, but the indirect valve can provide larger orifices (and therefore faster lift times) with reduced actuation requirements. Using a combination of analytical model-based and experimental methods, the SMART lift device with each valve approach was designed, and a full-scale prototype built and experimentally characterized validating the model and successfully demonstrating feasibility of each system to meet and exceed the pedestrian protection specifications. This new set of technologies enables the hood lift application with added functionality such as tailorability and resettability.

Modeling and sensitivity study of the dual-chamber SMART (SMA ReseTtable) lift device

Morphing structures for applications such as impact mitigation is a challenging problem due to the speed and repeatability requirements that limit the viable actuation approaches. This paper examines a promising stored-energy, active-release approach that can be deployed quickly (~40 ms), is reusable/resetable and can be tuned in the field for changing conditions such as additional mass, temperature compensation or platform changes. The Dual-Chamber SMART (SMA ReseTtable) Lift is a pneumatic air spring controlled via an ultra-fast SMA actuated valve. This paper presents the modeling, sensitivity analysis and experimental validation of this new technology. A control-volume based analytical model was derived that employs compressible, sonic flow and thermodynamic relations to provide a set of differential equations that relate the design parameters (cylinder and valve geometry), application parameters (deployed mass), and operational parameters (pressure, temperature and SMA valve actuation profile), to the deployment performance (deploy time, profile, position, etc.). The model was exercised to explore the sensitivity of the performance with regards to these parameters and explore the off-line and on-line adjustability of the devices performance to compensate for cross platform applications and uncontrolled environmental effects such as temperature and added mass. As proof-of-concept, a full-scale prototype was designed via the model, built and experimentally characterized across several of the parameters for the real case-study of automotive pedestrian protection. The prototype performance agreed closely with model predictions and met the rigorous specifications of the case study with in-situ tailoring which is applicable to a wide range of morphing applications beyond this case study.

The Design and Experimental Validation of an Ultrafast SMART (SMA Resettable) Latch

Latches are an essential machine element utilized by all sectors (medical, military, industrial, etc.) and there is a growing need for active latches with automatic release and reset capabilities. Shape memory alloy (SMA), due to its high energy/power densities, is an attractive alternative actuation approach to conventional methods (electrical, hydraulic) because it is inexpensive, lightweight, compact and has a fast heating response times. This paper introduces the T-latch which is based upon a compact spooled SMA rotary actuator. The T-latch can engage passively, maintain a structural connection in multiple degrees of freedom with zero power consumption, actively release very quickly (< 20 ms) and then repeat operation with automatic reset. To provide the basis to apply this latch across sectors, operational behavioral models are summarized for the key states of engagement, retention, release and reset. To demonstrate the technology, a proof-of-concept prototype for automotive panel lockdown was designed, built and experimentally characterized for the basic operational states along with studies of the effects of power, seal and reset force. The results from this study indicate promising suitability of the T-latch technology for a broad range of industrial applications.Copyright