Low Temperature Nitife Shape Memory Alloys: Actuator Engineering And Investigation Of Deformation Mechanisms Using In Situ Neutr

Shape memory alloys are incorporated as actuator elements due to their inherent ability to sense a change in temperature and actuate against external loads by undergoing a shape change as a result of a temperature-induced phase transformation. The cubic so-called austenite to the trigonal so-called R-phase transformation in NiTiFe shape memory alloys offers a practical temperature range for actuator operation at low temperatures, as it exhibits a narrow temperature-hysteresis with a desirable fatigue response. Overall, this work is an investigation of selected science and engineering aspects of low temperature NiTiFe shape memory alloys. The scientific study was performed using in situ neutron diffraction measurements at the newly developed low temperature loading capability on the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory and encompasses three aspects of the behavior of Ni46.8Ti50Fe3.2 at 92 K (the lowest steady state temperature attainable with the capability). First, in order to study deformation mechanisms in the R-phase in NiTiFe, measurements were performed at a constant temperature of 92 K under external loading. Second, with the objective of examining NiTiFe in one-time, high-stroke, actuator applications (such as in safety valves), a NiTiFe sample was strained to approximately 5% (the R-phase was transformed to B19\u27 phase in the process) at 92 K and subsequently heated to full strain recovery under a load. Third, with the objective of examining NiTiFe in cyclic, low-stroke, actuator applications (such as in cryogenic thermal switches), a NiTiFe sample was strained to 1% at 92 K and subsequently heated to full strain recovery under load. Neutron diffraction spectra were recorded at selected time and stress intervals during these experiments. The spectra were subsequently used to obtain quantitative information related to the phase-specific strain, texture and phase fraction evolution using the Rietveld technique. The mechanical characterization of NiTiFe alloys using the cryogenic capability at SMARTS provided considerable insight into the mechanisms of phase transformation and twinning at cryogenic temperatures. Both mechanisms contribute to shape memory and pseudoelasticity phenomena. Three phases (R, B19\u27 and B33 phases) were found to coexist at 92 K in the unloaded condition (nominal holding stress of 8 MPa). For the first time the elastic modulus of R-phase was reported from neutron diffraction experiments. Furthermore, for the first time a base-centered orthorhombic (B33) martensitic phase was identified experimentally in a NiTi-based shape memory alloy. The orthorhombic B33 phase has been theoretically predicted in NiTi from density function theory (DFT) calculations but hitherto has never been observed experimentally. The orthorhombic B33 phase was observed while observing shifting of a peak (identified to be B33) between the R and B19\u27 peaks in the diffraction spectra collected during loading. Given the existing ambiguity in the published literature as to whether the trigonal R-phase belongs to the P3 or P space groups, Rietveld analyses were separately carried out incorporating the symmetries associated with both space groups and the impact of this choice evaluated. The constrained recovery of the B19\u27 phase to the R-phase recorded approximately 4% strain recovery between 150 K and 170 K, with half of that recovery occurring between 160 K and 162 K. Additionally, the aforementioned research methodology developed for Ni46.8Ti50Fe3.2 shape memory alloys was applied to experiments performed on a new high temperature Ni29.5Ti50.5Pd20 shape memory alloys. The engineering aspect focused on the development of (i) a NiTiFe based thermal conduction switch that minimized the heat gradient across the shape memory actuator element, (ii) a NiTiFe based thermal conduction switch that incorporated the actuator element in the form of helical springs, and (iii) a NiTi based release mechanism. Patents are being filed for all the three shape memory actuators developed as a part of this work. This work was supported by grants from SRI, NASA (NAG3-2751) and NSF (CAREER DMR-0239512) to UCF. Additionally, this work benefited from the use of the Lujan Center at the Los Alamos Neutron Science Center, funded by the United States Department of Energy, Office of Basic Energy Sciences, under Contract No. W-7405-ENG-36

Shape memory thermal conduction switch

A thermal conduction switch includes a thermally-conductive first member having a first thermal contacting structure for securing the first member as a stationary member to a thermally regulated body or a body requiring thermal regulation. A movable thermally-conductive second member has a second thermal contacting surface. A thermally conductive coupler is interposed between the first member and the second member for thermally coupling the first member to the second member. At least one control spring is coupled between the first member and the second member. The control spring includes a NiTiFe comprising shape memory (SM) material that provides a phase change temperature <273 K, a transformation range <40 K, and a hysteresis of <10 K. A bias spring is between the first member and the second member. At the phase change the switch provides a distance change (displacement) between first and second member by at least 1 mm, such as 2 to 4 mm

Shape memory-based actuators and release mechanisms therefrom

SM-based actuators (110) and release mechanisms (100) therefrom and systems (500) including one or more release mechanisms (100). The actuators (110) comprise a SM member (118) and a deformable member (140) mechanically coupled to the SM member (118) which deforms upon a shape change of the SM member triggered by a phase transition of the SM member. A retaining element (160) is mechanically coupled to the deformable member (140), wherein the retaining element (160) moves upon the shape change. Release mechanism (100) include an actuator, a rotatable mechanism (120) including at least one restraining feature (178) for restraining rotational movement of the retaining element (160) before the shape change, and at least one spring (315) that provides at least one locked spring-loaded position when the retaining element is in the restraining feature and at least one released position that is reached when the retaining element is in a position beyond the restraining feature (178). The rotatable mechanism (120) includes at least one load-bearing protrusion (310). A hitch (400) is for mechanically coupling to the load, wherein the hitch is supported on the load bearing protrusion (310) when the rotatable mechanism is in the locked spring-loaded position

Role of synergy and immunostimulation in design of chemotherapy combinations: An analysis of doxorubicin and camptothecin

Combination chemotherapy is often employed to improve therapeutic efficacies of drugs. However, traditional combination regimens often utilize drugs at or near-their maximum tolerated doses (MTDs), elevating the risk of dose-related toxicity and impeding their clinical success. Further, high doses of adjuvant or neoadjuvant chemotherapies can cause myeloablation, which compromises the immune response and hinders the efficacy of chemotherapy as well as accompanying treatments such as immunotherapy. Clinical outcomes can be improved if chemotherapy combinations are designed to reduce the overall doses without compromising their therapeutic efficacy. To this end, we investigated a combination of camptothecin (CPT) with doxorubicin (DOX) as a low-dose treatment option for breast cancer. DOX-CPT combinations were synergistic in several breast cancer cell lines in vitro and one particular ratio displayed extremely high synergy on human triple negative breast cancer cells (MDA-MB-231). This combination led to excellent long-term survival of mice bearing MDA-MB-231 tumors at doses roughly five-fold lower than the reported MTD values of its constituent drugs. Impact of low dose DOX-CPT treatment on local tumor immune environment was assessed in immunocompetent mice bearing breast cancer (4T1) tumors. The combination was not only superior in inhibiting the disease progression compared to individual drugs, but it also generated a more favorable antitumor immunogenic response. Engineering DOX and CPT ratios to manifest synergy enables treatment at doses much lower than their MTDs, which could ultimately facilitate their translation into the clinic as a promising combination for breast cancer treatment. </div

Shape effect in active targeting of nanoparticles to inflamed cerebral endothelium under static and flow conditions

Endothelial cells represent the first biological barrier for compounds, including nanoparticles, administered via the intravascular route. In the case of ischemic stroke and other vascular diseases, the endothelium overexpresses specific markers, which can be used as molecular targets to facilitate drug delivery and imaging. However, targeting these markers can be quite challenging due to the presence of blood flow and the associated hydrodynamic forces, reducing the likelihood of adhesion to the vessel wall. To overcome these challenges, various parameters including size, shape, charge or ligand coating have been explored to increase the targeting efficiency. Geometric shape can modulate nanoparticle binding to the cell, especially by counteracting part of the hydrodynamic forces of the bloodstream encountered by the classical spherical shape. In this study, the binding affinity of polystyrene nanoparticles with two different shapes, spherical and rod-shaped, were compared. First, vascular adhesion molecule-1 (VCAM-1) was evaluated as a vascular target of inflammation, induced by lipopolysaccharide (LPS) stimulation. To evaluate the effect of nanoparticle shape on particle adhesion, nanoparticles were coated with anti-VCAM-1 and tested under static conditions in cell culture dishes coated with cerebral microvasculature cells (bEnd.3) and under dynamic flow conditions in microfluidic channels lined with hCMEC/D3 cells. Effect of particle shape on accumulation was also assessed in two in vivo models including systemic inflammation and local brain inflammation. The elongated rod-shaped particles demonstrated greater binding ability in vitro, reaching a 2.5-fold increase in the accumulation for static cultures and 1.5-fold for flow conditions. Anti-VCAM-1 coated rods exhibited a 3.5-fold increase in the brain accumulation compared to control rods. These results suggest shape offers a useful parameter in future design of drug delivery nanosystems or contrast agents for neurovascular pathologies.This study has been partially supported by grants from Instituto de Salud Carlos III (PI13/00292 and PI17/0054), Spanish ResearchNetwork on Cerebrovascular Diseases RETICS-INVICTUS (RD12/0014),Fundación Mutua Madrileña. The Ministry of Economy and Competitiveness of Spain (SAF2017-84267-R). The European Union program FEDER and the European Regional Development Fund–ERDF, MADIA project No. 732678 to FC. Furthermore, F. Campos (CP14/00154) recipients a research contract from Miguel Servet Program of Instituto de Salud Carlos III. National Science Foundation Graduate Research Fellowship under Grant DGE-1745303S

Propulsion From The Pulse Detonation Of Solid Propellant Pellet-Projectiles

Conventional solid propulsion is one of the oldest methods of propulsion that make use of deflagration phenomena rather than detonation to generate combustion gases. Proposed is a technology that makes use of detonation phenomena of solid propellents. This technology substantially departs from the conventional concepts and designs, and in doing so provides a system primarily developed for the purpose of providing a propulsion method that would have the advantages of both solid and liquid propulsion systems. The primary concept is that solid propellent pellets having a specific shape-profile is ejected in the form of projectiles having a certain velocity, interacts with a medium for initiation and the detonation of the solid propellent pellets takes place in flight. The velocity, the shape profile of the propellant pellets and the detonation process determines forward direction of the combustion gases evolved. The proposed technology has a specific application in space vehicle / space craft propulsion, and in military such as cruise missiles. Furthermore, variants of the proposed concept can be employed as in the case of detonation driven ramjets (dramjets) and detonation initiators for pulse detonation engines (PDEs)

Design, Fabrication And Testing Of A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

Shape memory alloys (SMAs) can recover large strains (e.g., up to 8%) by undergoing a temperature-induced phase transformation. This strain recovery can occur against large forces, resulting in their use as actuators. The SMA elements in such actuators integrate both sensory and actuation functions. This is possible because SMAs can inherently sense a change in temperature and actuate by undergoing a shape change, associated with the temperature-induced phase transformation. The objective of this work is to develop an SMA based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulk head arrangement for NASA. The design of the thermal conduction switch is based on a biased, two-way SMA actuator and utilizes a commercially available NiTi alloy as the SMA element to demonstrate the feasibility of this concept. This work describes the design from concept to implementation, addressing methodologies and issues encountered, including: a finite element based thermal analysis, various thermo-mechanical processes carried out on the NiTi SMA elements, and fabrication and testing of a prototype switch. Furthermore, recommendations for improvements and extension to NASA\u27s requirements are presented. Such a switch has potential application in variable thermal sinks to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. The SMA thermal conduction switch offers the following advantages over the currently used gas gap and liquid gap thermal switches in the cryogenic range: (i) integrates both sensor and actuator elements thereby reducing the overall complexity, (ii) exhibits superior thermal isolation in the open state, and (iii) possesses high heat transfer ratios between the open and closed states. This work was supported by a grant from NASA Kennedy Space Center (NAG10-323) with William U. Notardonato as Technical Officer

Mild and efficient bromination of poly(hydroxyethyl acrylate) and its use towards ionic-liquid containing polymers

International audienceAn original and mild bromination protocol allows a poly(hydroxyethyl acrylate) polymer synthesized by ATRP to be converted readily and quantitatively into its corresponding poly(bromoethyl acrylate) analogue. We show that the latter can be used as a common precursor towards ionic-liquid containing polymer