Small Density Changes Research Articles

LONG-TERM EVOLUTION OF MAGNETIC AND DYNAMICAL PROPERTIES IN A SUNSPOT LIGHT BRIDGE

Sunspot light bridges (LBs)—long bright lanes appearing in umbra—sometimes show dynamical behaviors such as plasma ejections, brightenings, and fast gas flows in the photosphere and lower chromosphere, but we have not understood what causes these dynamics. The Hinode Solar Optical Telescope successfully captured the entire period of the evolution of an LB formed at the southeast of the well-developed sunspot in NOAA Active Region 10953, allowing us to track how magnetic and dynamical properties change with time for 3.5 days. The LB produced chromospheric upward ejections intermittently and recurrently on 2007 April 30, and fewer upward ejections were observed on May 1. We found that G-band intensity features morphologically changed from cellar or patchy on April 30 to filamentary on May 1, although there were small changes in the magnetic flux density and inclination. This suggests that the chromospheric activity is related to the change of morphology in the photosphere. Fast gas flows and a pair of strong enhanced vertical electrical currents were also observed in the photosphere after the filamentary structures were dominant. The end of a large Hα filament (or prominence) was extended very close to the LB on May 1, suggesting that the filamentary structures formed along the LB may be magnetically connected to the large Hα filament and the gas flows may originate far from the LB region, although other mechanisms cannot be ruled out.

PULSED ALFVÉN WAVES IN THE SOLAR WIND

Using 3 s plasma and magnetic field data from the Wind spacecraft located in the solar wind well upstream from Earth, we report observations of isolated, pulse-like Alfvenic disturbances in the solar wind. These isolated events are characterized by roughly plane-polarized rotations in the solar wind magnetic field and velocity vectors away from the directions of the underlying field and velocity and then back again. They pass over Wind on timescales ranging from seconds to several minutes. These isolated, pulsed Alfven waves are pervasive; we have identified 175 such events over the full range of solar wind speeds (320-550 km s{sup -1}) observed in a randomly chosen 10 day interval. The large majority of these events are propagating away from the Sun in the solar wind rest frame. Maximum field rotations in the interval studied ranged from 6 Degree-Sign to 109 Degree-Sign . Similar to most Alfvenic fluctuations in the solar wind at 1 AU, the observed changes in velocity are typically less than that predicted for pure Alfven waves (Alfvenicity ranged from 0.28 to 0.93). Most of the events are associated with small enhancements or depressions in magnetic field strength and small changes in proton number density and/or temperature.more » The pulse-like and roughly symmetric nature of the magnetic field and velocity rotations in these events suggests that these Alfvenic disturbances are not evolving when observed. They thus appear to be, and probably are, solitary waves. It is presently uncertain how these waves originate, although they may evolve out of Alfvenic turbulence.« less

Investigating the structure of non-graphitising carbons using electron energy loss spectroscopy in the transmission electron microscope

We have investigated the structure and bonding in phenolic resin-based carbons as a function of heat treatment using a combination of high resolution transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, gas adsorption and density measurements. On heat treatment, the initially amorphous material transforms to a micro-porous material containing small graphitic packets enclosing elongated pores, with a relatively small change in density but an appreciable change in planar carbon sp 2-content as well as the development of significant curvature in the graphitic layers. The results from the different characterisation techniques are discussed and wherever possible, cross-correlated. They are also compared with proposed models for the microstructural development in non-graphitising carbons and also with the corresponding data obtained from graphitisable carbons. Overall the data provides strong evidence for a fullerene-based model for the microstructural development in non-graphitising carbons and more generally, the interpretation of the current EELS data has important implications for the spatially localised analysis of poorly crystalline carbon materials.

TU‐E‐220‐07: Using Breast Density as an Indicator of Side Effects and Change Induced by Tamoxifen and Radiation Treatment for Ductal Carcinoma in Situ

Purpose: Breast cancer kills more women in the United States than any other cancer except for lung cancer. Treatment is generally surgery followed by radiation therapy, chemotherapy and/or hormonal therapy. Many of these patients will have side effects to the treatment, including 80% of patients receiving radiation therapy, where 48% will have long term effects. The purpose of this paper is to identify if tracking breast density through treatment is possible, and if that breast density is indicative of side effects.Methods: Patient data were acquired from patients recruited into ongoing studies in accord with a Karmanos Cancer Institute and Wayne State University approved research protocol. Patients were selected if they exhibited a suspicious mass after mammography and/or follow‐up ultrasound. We tracked the patient volume‐averaged breast density throughout the course of treatment, starting on the first day of treatment. We recorded the volume‐averaged breast density of each breast generally once every week. To analyze this data, we plot the left and right volume‐averaged breast density to determine if and how the breast density is changing. We used excel to determine the slope (the change of volume‐averaged breast density in km/s vs. time in s) and the coefficient of determination (r2) for our data. Results: Our results show that the change in breast density over the course of radiation treatment, Tamoxifen treatment, and a combination of the two, is measureable. Conclusions: We can detect a small change in breast density, in‐vivo, on a weekly basis, throughout the course of treatment. The limitation to this study is the small number of patients, in this study only 5. Future studies are needed to determine the significance of our results. Currently, we believe that edema, and possibly fibrosis would be observable, which will be shown in future studies.

Long-term in-vitro precision of direct digital X-ray radiogrammetry.

ObjectiveDigital X-ray radiogrammetry (DXR) calculates peripheral bone mineral density (BMD) from hand radiographs. The short-term precision for direct DXR has been reported to be highly satisfactory. However, long-term precision for this method has not been examined. Thus, the aim of this study was to examine the long-term in-vitro precision for the new direct digital version of DXR.Materials and methodsThe in-vitro precision for direct DXR was tested with cadaver phantoms on four different X-ray systems at baseline, 3 months, 6 months, and in one machine also at 12 months. At each time point, 31 measurements were performed.ResultsThe in-vitro longitudinal precision for the four radiographic systems ranged from 0.22 to 0.43% expressed as coefficient of variation (CV%). The smallest detectable difference (SDD) ranged from 0.0034 to 0.0054 g/cm2.ConclusionsThe in vitro long-term precision for direct DXR was comparable to the previous reported short-term in-vitro precision for all tested X-ray systems. These data show that DXR is a stable method for detecting small changes in bone density during 6–12 months of follow-up.

The unconstrained local hardness: an intriguing quantity, beset by problems

Developing a mathematical approach to the local hard/soft acid/base principle requires an unambiguous definition for the local hardness. One such quantity, which has aroused significant interest in recent years, is the unconstrained local hardness. Key identities are derived for the unconstrained local hardness, δμ/δρ(r). Several identities are presented which allow one to determine the unconstrained local hardness either explicitly using the hardness kernel and the inverse-linear response function, or implicitly by solving a system of linear equations. One result of this analysis is that the problem of determining the unconstrained local hardness is infinitely ill-conditioned because arbitrarily small changes in electron density can cause enormous changes in the chemical potential. This is manifest in the exponential divergence of the unconstrained local hardness as one moves away from the system. This suggests that one should be very careful when using the unconstrained local hardness for chemical interpretation.

Flow rate measurement by an orifice in a slowly reciprocating gas flow

It is shown that small density changes can give rise to misinterpretation of flow rate signals in unsteady (reciprocating) flows. Basically a flow rate measured at some point A cannot simply be assigned to a remote point B . Depending on the way of plotting a hysteresis appears which, in fact, does not exist. Unsteady conservation of mass is applied to a volume and orifice flow system to obtain an equation which explains and predicts the apparent hysteresis. The equation in dimensionless form contains a key parameter β which holds the flow determining quantities. Experiments are conducted with respect to a wide spread of β . It is shown that the equation predicts reality quite well.

Interplay of electron–phonon interaction and strong correlations: [formula omitted] approach

We discuss interaction of strongly correlated electrons (described within the Hubbard model solved by dynamical mean-field theory (DMFT)) with Debye and Einstein phonons using recently developed DMFT+Σ computational scheme. Electron–phonon interaction (EPI) is analyzed in adiabatic approximation (assuming the validity of Migdal theorem), allowing the neglect of EPI vertex corrections. This approach is valid for EPI coupling constant λ<ɛF/ωph∼10, where ɛF is Fermi energy and ωph is Debye or Einstein frequency. For moderate values of λ only small changes in the electronic density of states are observed in DMFT+Σ approximation for both weakly and strongly correlated metallic regimes. Metal–insulator (Mott) transition due to the increase of Hubbard interaction U is slightly inhibited by EPI. Our main aim is to discuss the interplay of “kinks” in electronic dispersion due to EPI and recently discovered kinks of electronic origin. For the certain region of model parameters coexistence of phonon “kinks” in electronic dispersion with purely electronic “kinks” is readily observed and we formulate some simple criteria of such coexistence. However, for most general combinations of model parameters phonon “kinks” make electronic “kinks” hardly observable. In the general case an increase of Hubbard interaction U rapidly suppresses the slope of electronic dispersion within the phonon “kink.” These results are important for deeper understanding of the shape and evolution of electronic dispersions in strongly correlated systems such as copper oxides, where different kinds of “kinks” were recently observed in ARPES experiments.

Piezoelectric cantilever sensors with asymmetric anchor exhibit picogram sensitivity in liquids

We show for the first time that self-exciting and self-sensing piezoelectric cantilevers consisting only of lead zirconate titanate (PZT) measure resonance only if they are asymmetrically anchored. Symmetric-anchoring did not give rise to electrically measurable bending resonant modes in the 0–100 kHz range. Sensitivity of first and second bending mode resonances was characterized in a flow apparatus using small density changes in liquid (0.003–0.01 g/cm 3) and by dodecanethiol chemisorption at 30 pM. Density change results were consistent with existing models of submerged cantilevers, and yielded mass-change sensitivity of ∼33 ng/Hz and 217 pg/Hz for the first two modes. In chemisorption experiments, where binding was localized to 1 mm 2 distal tip of the PZT cantilever, sensitivity improved by an order of magnitude to 2 pg/Hz and 414 fg/Hz for the same two resonant modes.

Enhanced density estimation from prestack inversion of multicomponent seismic data

Using 3C-2D seismic data in the Albacora block, Campos Basin, Brazil, we analyzed the potential of multicomponent data for density esti-mation by simultaneously inverting prestack compressional and mode-converted seismic data. Initial forward modeling using the available well logs shows that small changes in density at the reservoir level affect the PS reflectivity more than PP. The inversion engine uses a global optimization algorithm with a nonlinear cost function to simultaneously invert a number of in-put stacks to an Earth model. Inverting solely PP data has shown a lower cor-relation between the estimated density and the measured log in comparison to jointly inverting both PP and PS data. The results also show that adding PS information in the inversion pro-cess improves the density inversion bandwidth and, consequently, inversion resolution.

Ab initio studies of ultrafast x-ray scattering of the photodissociation of iodine

We computationally examine various aspects of the reaction dynamics of the photodissociation and recombination of molecular iodine. We use our recently proposed formalism to calculate time-dependent x-ray scattering signal changes from first principles. Different aspects of the dynamics of this prototypical reaction are studied, such as coherent and noncoherent processes, features of structural relaxation that are periodic in time versus nonperiodic dissociative processes, as well as small electron density changes caused by electronic excitation, all with respect to x-ray scattering. We can demonstrate that wide-angle x-ray scattering offers a possibility to study the changes in electron densities in nonperiodic systems, which render it a suitable technique for the investigation of chemical reactions from a structural dynamics point of view.

Variation in quantitative sensory testing and epidermal nerve fiber density in repeated measurements

Quantitative sensory testing (QST) is commonly used to evaluate peripheral sensory function in neuropathic conditions. QST measures vary in repeated measurements of normal subjects but it is not known whether QST can reflect small changes in epidermal nerve fiber density (ENFd). This study evaluated QST measures (touch, mechanical pain, heat pain and innocuous cold sensations) for differences between genders and over time using ENFd as an objective-independent measure. QST was performed on the thighs of 36 healthy volunteers on four occasions between December and May. ENFd in skin biopsies was determined on three of those visits. Compared to men, women had a higher ENFd, a difference of 12.2 ENFs/mm. They also had lower tactile and innocuous cold thresholds, and detected mechanical pain (pinprick) at a higher frequency. Heat pain thresholds did not differ between genders. By the end of the 24-week study, men and women showed a small reduction (p<0.05) in the frequency of sharp mechanical pain evoked by pinprick whereas tactile and thermal thresholds showed no change. This coincided with a small decrease in ENFd, 4.18 ENFs/mm. Variation in measurements over time was large in a fraction of normal subjects. We conclude that most QST measures detect relatively large differences in epidermal innervation (12.2 ENFs/mm), but response to mechanical pain was the only sensory modality tested with the sensitivity to detect small changes in innervation (4.18 ENFs/mm). Since some individuals had large unsystematic variations, unexpected test results should therefore alert clinicians to test additional locations.

Morphological characterization of soot aerosol particles during LACIS Experiment in November (LExNo)

Combined mobility and aerodynamic measurements were used to characterize the morphology of soot particles in an experimental campaign on the hygroscopic growth and activation of an artificial biomass burning aerosol. A custom‐made, single‐stage low‐pressure impactor and two aerosol mass spectrometers (AMS) operating in the free molecular regime were used to measure the vacuum aerodynamic diameter of mobility‐selected artificial soot particles that were produced in a spark discharge generator and then modified by condensation of ammonium hydrogen sulfate or levoglucosan as a coating to change their hydroscopic activity. Transmission electron microscope images revealed a relationship between the electrical mobility diameter and the diameter of the enveloping sphere, thus enabling evaluation of the effective density of soot agglomerates. A fractal description of the morphology of the soot aggregates allowed for evaluation of the average mass of the hygroscopic material per particle. The average mass of the hygroscopic material per particle was also measured directly with the two AMS instruments, and the agreement between the two methods was found satisfactory. This tandem approach allows detection of small changes in the particle effective density and morphology caused by condensation of organic material.

Changes in Sahelian bird biodiversity and tree density over a five‐year period in northern Nigeria

Capsule Two widespread censuses of already degraded woodland in the Sahel in Northern Nigeria separated by five years (2002 and 2007) showed relatively small further changes in tree and bird density. Aims To determine how change in tree density affects African and Palearctic migrant bird density in already degraded Sahelian woodland. Methods We compared differences in the number of bird species and their abundance with differences in the size and number of woody plants between two seasons separated by five years at 16 degraded woodland sites across 250 km east–west in northern Nigeria. Results Densities of large trees (>5 m) decreased, but densities of smaller trees and shrubs increased, partly as a consequence of growth and because larger trees have been preferentially removed or partly cut down; tree densities were, however, initially low. Of 37 common bird species, 16% had higher densities and 22% had lower densities, in the second study period. The density of Common Whitethroats, Northern Wheatears and Yellow Wagtails was correlated with the number and size of trees, but not that of Lesser Whitethroat and Subalpine Warbler. Overall there was relatively little turnover in species between the two surveys and if (the initially low) tree density was halved, only approximately 2.1% of the average total for number of bird species per 0.2 ha point would be lost. Conclusion Few large changes in bird species' density were found, possibly because: (1) all habitats sampled were already at relatively low tree density – initial reductions from high tree density or near removal of all trees may cause larger changes in local bird densities; (2) reduction in the number of large trees was partially compensated by a more lush development of the vegetation as a whole in the second study period; and (3) the bird species remaining in degraded Sahelian woodland in northern Nigeria are already well adapted to habitat change and low tree density.

Vortex-induced instabilities and accelerated collapse due to inertial effects of density stratification

A vortex placed at a density interface winds it into an ever-tighter spiral. We show that this results in a combination of a centrifugal Rayleigh–Taylor (CRT) instability and a spiral Kelvin–Helmholtz (SKH) type of instability. The SKH instability arises because the density interface is not exactly circular, and dominates at large times. Our analytical study of an inviscid idealized problem illustrates the origin and nature of the instabilities. In particular, the SKH is shown to grow slightly faster than exponentially. The predicted form lends itself for checking by a large computation. From a viscous stability analysis using a finite-cored vortex, it is found that the dominant azimuthal wavenumber is smaller for lower Reynolds number. At higher Reynolds numbers, disturbances subject to the combined CRT and SKH instabilities grow rapidly, on the inertial time scale, while the flow stabilizes at low Reynolds numbers. Our direct numerical simulations are in good agreement with these studies in the initial stages, after which nonlinearities take over. At Atwood numbers of 0.1 or more, and a Reynolds number of 6000 or greater, both stability analysis and simulations show a rapid destabilization. The result is an erosion of the core, and breakdown into a turbulence-like state. In studies at low Atwood numbers, the effect of density on the inertial terms is often ignored, and the density field behaves like a passive scalar in the absence of gravity. The present study shows that such treatment is unjustified in the vicinity of a vortex, even for small changes in density when the density stratification is across a thin layer. The study would have relevance to any high-Péclet-number flow where a vortex is in the vicinity of a density-stratified interface.

Ion irradiation stability of multilayered AlN/TiN nanocomposites

Structural changes in multilayered AlN/TiN nanocomposites upon Ar+ ion irradiation were investigated. Reactive sputtering was used to deposit (AlN/TiN) × 5 multilayers on Si(1 0 0), to a total thickness of ∼270 nm. Argon was implanted at 200 keV, to 5 × 1015–4 × 1016 ions cm−2. The as-deposited multilayers had a very fine columnar nanocrystalline structure, the width of individual grains was up to ∼10 nm. It was found that this immiscible system exhibits a high ion radiation stability, the AlN and TiN layers remaining well separated, with sharp interfaces. Ion irradiation induced small local density changes and only a slight increase in individual grains, in the region where most damage was deposited by the impact ions. For the highest irradiation fluence there was also some migration of Ti into AlN in this region, which was assigned to excess nitrogen within the AlN layers. Due to these small structural changes, ion irradiation enhanced the mechanical strength of the multilayered nanocomposites.

A SAXS Study of Hydrogenated Nanocrystalline Silicon Thin Films

AbstractWe have used small-angle x-ray scattering (SAXS) in conjunction with X-ray diffraction (XRD) to study the nanostructure of hydrogenated nanocrystalline silicon (nc-Si:H). The crystallite size in the growth direction, as deduced from XRD data, is 24 nm with a preferred [220] orientation in the growth direction of the film. Fitting the SAXS intensity shows that the scattering derives from electron density fluctuations of both voids in the amorphous phase and H-rich clusters in the film, probably at the crystallite interfaces. The SAXS results indicate ellipsoidal shaped crystallites about 6 nm in size perpendicular to the growth direction. We annealed the samples, stepwise, and then measured the SAXS and ESR. At temperatures below 350◦C, we observe an overall increase in the size of the scattering centers on annealing but only a small change in the spin density, which suggests that bond reconstruction on the crystallite surfaces takes place with high efficacy.

Reduction of Breast Density Following Tamoxifen Treatment Evaluated by 3-D MRI.

Abstract Background: It has been reported that MRI-based density measurement is more sensitive than mammographic density to evaluate the small changes of breast density. This study analyzed the change of breast density in women receiving tamoxifen treatment using 3-D MRI.Material and Methods: Twenty-two breasts in 20 women were studied. Two MRI studies were performed at 1.5T, the baseline scan acquired after surgery and prior to receiving tamoxifen, and the follow-up scan at 10 months to 30 months after tamoxifen treatment. Non-fat-suppression T1-weighted images were used for the density measurement. The breast and the fibroglandular tissue were segmented using a computer-assisted algorithm recently published by our group. For each breast, the total fibroglandular tissue volume and the total breast volume were calculated, and then the ratio was calculated as the percent breast density (%BD). The changes in breast volume, fibroglandular tissue volume, and the percent density in the F/U scan compared to the B/L scan were evaluated. The reduction in the fibroglandular volume (ΔFV=FV2-FV1, ml), and in the percent breast density (Δ%BD= %BD2-%BD1) were analyzed.Results: The total breast volume did not show significant changes between F/U and B/L. For analysis of fibroglandular volume, 20 breasts showed volume reduction and 2 showed slight increase of volume. Overall, the mean ΔFV was 20.7ml, with 33% reduction. The ΔFV was correlated with the baseline FV (r=0.82) (Figure 1), indicating that when the fibroglandular tissue volume was higher, more reduction was found.For analysis of %BD, 19 breasts showed reduction, and 3 showed increased density, with a mean Δ%BD of 4.7%. The 22 breasts were further divided into three categories based on their B/L density as: fatty breast (%BD&amp;lt; 8%, N=4), moderately dense breast (%BD 8-20%, N=9), and dense breast (%BD &amp;gt;20%, N=9). The amount of density reduction was associated with the B/L density, showing 10.9, 17.2, and 28.6 ml for ΔFV; and 1.2%, 3.9%, and 7.2% for Δ%BD respectively in these 3 groups. Statistically, only Δ%BD between the fatty and the dense groups showed a significant difference (P=0.02).Discussion: MRI provides strong soft tissue contrast, thus it may have advantages for revealing detailed density distribution compared to mammography. The %BD can be measured by normalizing the FV to the total breast volume, analogous to the mammographic density. However, this will be subjective to the variations in the measurement of breast volume. The FV within the breast was a more robust parameter, which showed reduction in 20 of 22 breasts with a mean reduction of 33%, also a significant correlation with B/L FV. The reduction of density is expected to be through decreased hormonal level in the breast, and the reduction of fibroglandular tissue density should be correlated with the baseline density. Our results are consistent with this expectation, and demonstrate that MRI can be used to evaluate the density change induced by tamoxifen. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4021.

Breast density analysis for whole breast ultrasound images

Breast density has been established as an independent risk factor associated with the development of breast cancer. The terms mammographic density and breast density are often used interchangeably, since most breast density studies are performed with projection mammography. It is known that increase in mammographic density is associated with an increased cancer risk. A sensitive method that allows for the measurement of small changes in breast density may provide useful information for risk management. Despite the efforts to develop quantitative breast density measurements from projection mammograms, the measurements show large variability as a result of projection imaging, differing body position, differing levels of compression, and variation of the x-ray beam characteristics. This study used two separate computer-aided methods, threshold-based and proportion-based evaluations, to analyze breast density on whole breast ultrasound (US) imaging and to compare with the grading results of three radiologists using projection mammography. Thirty-two female subjects with 252 images per case were included in this study. Whole breast US images were obtained from an Aloka SSD-5500 ultrasound machine with an ASU-1004 transducer (Aloka, Japan). Before analyzing breast density, an adaptive speckle reduction filter was used for removing speckle noise, and a robust thresholding algorithm was used to divide breast tissue into fatty or fibroglandular classifications. Then, the proposed approaches were applied for analysis. In the threshold-based method, a statistical model was employed to determine whether each pixel in the breast region belonged to fibroglandular or fatty tissue. The proportion-based method was based on three-dimensional information to calculate the volumetric proportion of fibroglandular tissue to the total breast tissue. The experimental cases were graded by the proposed analysis methods and compared with the ground standard density classification assigned by a majority voting of three experienced breast radiologists. For the threshold-based method, 28 of 32 US test cases and for the proportion-based density classifier, 27 of 32 US test cases were found to be in agreement with the radiologist "ground standard" mammographic interpretations, resulting in overall accuracies of 87.5% and 84.4%, respectively. Moreover, the concordance values of the proposed methods were between 0.0938 and 0.1563, which were less than the average interobserver concordance of 0.3958. The experiment result showed that the proposed methods could be a reference opinion and offer concordant and reliable quantification of breast density for the radiologist.

Stem cell antigen‐1+ cell‐based bone morphogenetic protein‐4 gene transfer strategy in mice failed to promote endosteal bone formation

This study assessed whether a Sca-1+ cell-based ex vivo gene transfer strategy, which has been shown to promote robust endosteal bone formation with a modified fibroblast growth factor-2 (FGF2) gene, can be extended to use with bone morphogenetic protein (BMP)2/4 hybrid gene. Sublethally irradiated recipient mice were transplanted with lentiviral (LV)-BMP2/4-transduced Sca-1+ cells. Bone parameters were monitored by pQCT and microCT. Gene expression was assessed by the real-time reverse transcriptase-polymerase chain reaction. Recipient mice of LV-BMP2/4-transduced Sca-1+ cells yielded high engraftment and increased BMP4 mRNA levels in marrow cells; but exhibited only insignificant increases in serum and bone alkaline phosphatase activity compared to control mice. pQCT and microCT analyses of femurs showed that, with the exception of small changes in trabecular bone mineral density and cortical bone mineral content in LV-BMP2/4 mice, there were no differences in measured bone parameters between mice of the LV-BMP2/4 group and controls. The lack of large endosteal bone formation effects with the BMP4 strategy could not be attributed to ineffective engraftment or expansion of BMP4-expressing Sca-1+ cells, an inability of the transduced cells to secrete active BMP4 proteins, or to use of the LV-based vector. Sca-1+ cell-based BMP4 ex vivo strategy did not promote robust endosteal bone formation, raising the possibility of intrinsic differences between FGF2- and BMP4-based strategies in their ability to promote endosteal bone formation. It emphasizes the importance of choosing an appropriate bone growth factor gene for delivery by this Sca-1+ cell-based ex vivo systemic gene transfer strategy to promote bone formation.