Electron and stochastic cooling are proven methods for cooling low-energy hadron beams, but at present there is no way of cooling hadrons as they near the TeV scale. In the 1980s, Derbenev suggested ...that electron instabilities, such as free-electron lasers, could create collective space charge fields strong enough to correct the hadron energies. This Letter presents a variation on Derbenev's electron cooling scheme using the microbunching instability as the amplifier. The large bandwidth of the instability allows for faster cooling of high-density beams. A simple analytical model illustrates the cooling mechanism, and simulations show cooling rates for realistic parameters of the Large Hadron Collider.
Abstract The biomaterials community has been unable to accurately assign the term “blood compatible” to a biomaterial in spite of 50 years of intensive research on the subject. There is no clear ...consensus as to which materials are “blood compatible.” There are no standardized methods to assess blood compatibility. Since we use millions of devices in contact with blood each year, it is imperative we give serious thought to this intellectual catastrophe. In this perspective, I consider five hypotheses as to why progress has been slow in evolving a clear understanding of blood compatibility: Hypothesis 1—It is impossible to make a blood compatible material. Hypothesis 2—We do not understand the biology behind blood compatibility. Hypothesis 3—We do not understand how to test for or evaluate blood compatibility. Hypothesis 4—Certain materials of natural origin seem to show better blood compatibility but we do not know how to exploit this concept. Hypothesis 5—We now have better blood compatible materials but the regulatory and economic climate prevent adoption in clinical practice.
Abstract The host response to biomaterials has been studied for decades. Largely, the interaction of host immune cells, macrophages in particular, with implanted materials has been considered to be a ...precursor to granulation tissue formation, the classic foreign body reaction, and eventual encapsulation with associated negative impacts upon device functionality. However, more recently, it has been shown that macrophages, depending upon context dependent polarization profiles, are capable of affecting both detrimental and beneficial outcomes in a number of disease processes and in tissue remodeling following injury. Herein, the diverse roles played by macrophages in these processes are discussed in addition to the potential manipulation of macrophage effector mechanisms as a strategy for promoting site-appropriate and constructive tissue remodeling as opposed to deleterious persistent inflammation and scar tissue formation.
The foreign body reaction (FBR) to implanted materials is of critical importance when medical devices require biological integration and vascularization to support their proper function (e.g., ...transcutaneous devices, implanted drug delivery systems, tissue replacements, and sensors). One class of materials that improves FBR outcomes is made by sphere-templating, resulting in porous structures with uniform, interconnected 34
μ
m pores. With these materials we observe reduced fibrosis and increased vascularization. We hypothesized that improved healing is a result of a shift in macrophage polarization, often measured as the ratio of M1 pro-inflammatory cells to M2 pro-healing cells. In this study, macrophage polarity of 34
μ
m porous implants was compared to non-porous and 160
μ
m porous implants in subcutaneous mouse tissue. Immunohistochemistry revealed that macrophages in implant pores displayed a shift towards an M1 phenotype compared to externalized cells. Macrophages in 34
μ
m porous implants had up to 63% greater expression of M1 markers and up to 85% reduction in M2 marker expression (
p
< 0.05). Macrophages immediately outside the porous structure, in contrast, showed a significant enrichment in M2 phenotypic cells. This study supports a role for macrophage polarization in driving the FBR to implanted materials.
The performance of implantable biomedical devices is impeded by the foreign-body reaction, which results in formation of a dense collagenous capsule that blocks mass transport and/or electric ...communication between the implant and the body. No known materials or coatings can completely prevent capsule formation. Here we demonstrate that ultra-low-fouling zwitterionic hydrogels can resist the formation of a capsule for at least 3 months after subcutaneous implantation in mice. Zwitterionic hydrogels also promote angiogenesis in surrounding tissue, perhaps owing to the presence of macrophages exhibiting phenotypes associated with anti-inflammatory, pro-healing functions. Thus, zwitterionic hydrogels may be useful in a broad range of applications, including generation of biocompatible implantable medical devices and tissue scaffolds.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Since its inception just over a half century ago, the field of biomaterials has seen a consistent growth with a steady introduction of new ideas and productive branches. This review describes where ...we have been, the state of the art today, and where we might be in 10 or 20 years. Herein, we highlight some of the latest advancements in biomaterials that aim to control biological responses and ultimately heal. This new generation of biomaterials includes surface modification of materials to overcome nonspecific protein adsorption in vivo, precision immobilization of signaling groups on surfaces, development of synthetic materials with controlled properties for drug and cell carriers, biologically inspired materials that mimic natural processes, and design of sophisticated three-dimensional (3-D) architectures to produce well-defined patterns for diagnostics, e.g., biological microelectromechanical systems (bioMEMs), and tissue engineering.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Structural rearrangements within single molecules occur on ultrafast time scales. Many aspects of molecular dynamics, such as the energy flow through excited states, have been studied using ...spectroscopic techniques, yet the goal to watch molecules evolve their geometrical structure in real time remains challenging. By mapping nuclear motions using femtosecond x-ray pulses, we have created real-space representations of the evolving dynamics during a well-known chemical reaction and show a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-ray scattering. A computational analysis optimally matches the series of scattering patterns produced by the x rays to a multitude of potential reaction paths. In so doing, we have made a critical step toward the goal of viewing chemical reactions on femtosecond time scales, opening a new direction in studies of ultrafast chemical reactions in the gas phase.
The recently commissioned Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness ...nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs (10-15 s). With these beam characteristics this light source is capable of imaging the structure and dynamics of matter at atomic size and timescales. The facility is now operating at X-ray wavelengths from 22 to 1.2 A and is presently delivering this high-brilliance beam to a growing array of scientific researchers. We describe the operation and performance of this new 'fourth-generation light source'.
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