Technology requirements for advanced earth-orbital transportation systems, dual-mode propulsion

The application of dual-mode propulsion concepts to fully reusable single-stage-to-orbit (SSTO) vehicles is discussed. Dual-mode propulsion uses main rocket engines that consume hydrocarbon fuels as well as liquid hydrogen fuel. Liquid oxygen is used as the oxidizer. These engine concepts were integrated into transportation vehicle designs capable of vertical takeoff, delivering a payload to earth orbit, and return to earth with a horizontal landing. Benefits of these vehicles were assessed and compared with vehicles using single-mode propulsion (liquid hydrogen and oxygen engines). Technology requirements for such advanced transportation systems were identified. Figures of merit, including life-cycle cost savings and research costs, were derived for dual-mode technology programs, and were used for assessments of potential benefits of proposed technology activities. Dual-mode propulsion concepts display potential for significant cost and performance benefits when applied to SSTO vehicles

Technology requirements for advanced earth-orbital transportation systems: Summary report

Areas of advanced technology that are either critical or offer significant benefits to the development of future Earth-orbit transportation systems were identified. Technology assessment was based on the application of these technologies to fully reusable, single-state-to-orbit (SSTO) vehicle concepts with horizontal landing capability. Study guidelines included mission requirements similar to space shuttle, an operational capability beginning in 1995, and main propulsion to be advanced hydrogen-fueled rocket engines. The technical and economic feasibility of this class of SSTO concepts were evaluated as well as the comparative features of three operational take-off modes, which were vertical boost, horizontal sled launch, and horizontal take-off with subsequent inflight fueling. Projections of both normal and accelerated technology growth were made. Figures of merit were derived to provide relative rankings of technology areas. The influence of selected accelerated areas on vehicle design and program costs was analyzed by developing near-optimum point designs

Chiral Perturbation Theory with tensor sources

We construct the most general chirally-invariant Lagrangian for mesons in the presence of external sources coupled to the tensor current \bar{\psi}\sigma_{\mu\nu}\psi. In order to have only even terms in the chiral expansion, we consider the new source of O(p^2). With this choice, we build the even-parity effective Lagrangian up to the p^6-order (NLO). While there are only 4 new terms at the p^4-order, at p^6-order we find 78 terms for n_f=2 and 113 terms for n_f=3. We provide a detailed discussion on the different mechanisms that ensure that our final set of operators is complete and non-redundant. We also examine the odd-parity sector, to conclude that the first operators appear at the p^8-order (NNLO).Comment: 23 pages, one figure; typos corrected, one paragraph added, new section added, references added, published versio

On the two-loop contributions to the pion mass

We derive a simplified representation for the pion mass to two loops in three-flavour chiral perturbation theory. For this purpose, we first determine the reduced expressions for the tensorial two-loop 2-point sunset integrals arising in chiral perturbation theory calculations. Making use of those relations, we obtain the expression for the pion mass in terms of the minimal set of master integrals. On the basis of known results for these, we arrive at an explicit analytic representation, up to the contribution from K-K-eta intermediate states where a closed-form expression for the corresponding sunset integral is missing. However, the expansion of this function for a small pion mass leads to a simple representation which yields a very accurate approximation of this contribution. Finally, we also give a discussion of the numerical implications of our results.Comment: Typos corrected and minor changes in Table 2. Published version. 19 pages, 1 figure, 2 table

Temporal and spatial patterns of cortical activation during assisted lower limb movement

Human gait is a complex process in the central nervous system that results from the integrity of various mechanisms, including different cortical and subcortical structures. In the present study, we investigated cortical activity during lower limb movement using EEG. Assisted by a dynamic tilt table, all subjects performed standardized stepping movements in an upright position. Source localization of the movement-related potential in relation to spontaneous EEG showed activity in brain regions classically associated with human gait such as the primary motor cortex, the premotor cortex, the supplementary motor cortex, the cingulate cortex, the primary somatosensory cortex and the somatosensory association cortex. Further, we observed a task-related power decrease in the alpha and beta frequency band at electrodes overlying the leg motor area. A temporal activation and deactivation of the involved brain regions as well as the chronological sequence of the movement-related potential could be mapped to specific phases of the gait-like leg movement. We showed that most cortical capacity is needed for changing the direction between the flexion and extension phase. An enhanced understanding of the human gait will provide a basis to improve applications in the field of neurorehabilitation and brain-computer interface

Integrating out the heaviest quark in N--flavour ChPT

We extend a known method to integrate out the strange quark in three flavour chiral perturbation theory to the context of an arbitrary number of flavours. As an application, we present the explicit formulae to one--loop accuracy for the heavy quark mass dependency of the low energy constants after decreasing the number of flavours by one while integrating out the heaviest quark in N--flavour chiral perturbation theory.Comment: 18 pages, 1 figure. Text and references added. To appear in EPJ

2D vs. 3D pain visualization: User preferences in a spinal cord injury cohort

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 Springer VerlagResearch on pain experienced after Spinal Cord Injury (SCI) has revealed that not only are there several types of pain present in the same individual with this kind of trauma, but also that people who suffer such an injury can describe the characteristics of the same type of pain in different ways. Making it possible, therefore, to more precisely describe pain experience could prove to be vital for an increased quality of life. Accordingly, fifteen individuals with pain after SCI were asked to describe their pain experience using a 3 Dimensional (3D) model of the human body that could be used as an aid in communicating their pain. The results of this study suggest that the consensus of the participants approved the ability of the 3D model to more accurately describe their pain, an encouraging outcome towards the use of 3D technology in support of post SCI pain rehabilitation

Integrating out strange quarks in ChPT

We study three flavour chiral perturbation theory in a limit where the strange quark mass is much larger than the external momenta and the up and down quark masses, and where the external fields are those of two-flavour chiral perturbation theory. In this case, the theory reduces to the one of SU(2)_L x SU(2)_R. Through this reduction, one can work out the strange quark mass dependence of the LECs in the two-flavour case. We present the pertinent relations at two-loop order for F,B and l_i.Comment: 14 pages, 3 figures, References added. Due to a typo in a form program, we missed a finite, scale independent part in l_7. Is now included. Version to appear in Phys.Lett.

What comprises a good outcome in spinal surgery? A preliminary survey among spine surgeons of the SSE and European spine patients

Standardized and validated self-administered outcome-instruments are broadly used in spinal surgery. Despite a plethora of articles on outcome research, no systematic evaluation is available on what actually comprises a good outcome in spinal surgery from the patients' and surgeons' perspective, respectively. However, this is a prerequisite for improving outcome instruments. In performing a cross-sectional survey among spine patients from different European regions and spine surgeons of the SSE, the study attempted (1) to identify the most important domains determining a good outcome from a patients' as well as a surgeon's perspective, and (2) to explore regional differences in the identified domains. For this purpose, a structured interview was performed among 30 spine surgeons of the SSE and 353 spine surgery patients (representing Northern, Central and Southern Europe) to investigate their criteria for a good outcome. A qualitative and descriptive approach was used to evaluate the data. Results revealed a high agreement on what comprises a good outcome among surgeons and patients, respectively. The main parameters determining good outcome were achieving the patients' expectations/satisfaction, pain relief, improvement of disability and social reintegration. Younger patients more often expected a complete pain relief, an improved work capacity, and better social life participation. Patients in southern Europe more often wanted to improve work capacity compared to those from central and northern European countries. No substantial differences were found when patients' and surgeons' perspective were compared. However, age and differences in national social security and health care system ("black flags”) have an impact on what is considered a good outcome in spinal surger