Value Of Form Factor Research Articles

Couplings of light I=0 scalar mesons to simple operators in the complex plane

The flavour and glue structure of the light scalar mesons in QCD are probed by studying the couplings of the I=0 mesons $\sigma(600)$ and $f_0(980)$ to the operators $\bar{q}q$, $\alpha_s G^2$ and to two photons. The Roy dispersive representation for the $\pi\pi$ amplitude $t_0^0(s)$ is used to determine the pole positions as well as the residues in the complex plane. On the real axis, $t_0^0$ is constrained to solve the Roy equation together with elastic unitarity up to the $K\Kbar$ threshold leading to an improved description of the $f_0(980)$. The problem of using a two-particle threshold as a matching point is discussed. A simple relation is established between the coupling of a scalar meson to an operator $j_S$ and the value of the related pion form-factor computed at the resonance pole. Pion scalar form-factors as well as two-photon partial-wave amplitudes are expressed as coupled-channel Omn\`es dispersive representations. Subtraction constants are constrained by chiral symmetry and experimental data. Comparison of our results for the $\bar{q}q$ couplings with earlier determinations of the analogous couplings of the lightest I=1 and $I=1/2$ scalar mesons are compatible with an assignment of the $\sigma$, $\kappa$, $a_0(980)$, $f_0(980)$ into a nonet. Concerning the gluonic operator $\alpha_s G^2$ we find a significant coupling to both the $\sigma$ and the $f_0(980)$.

High Glucose Induces Mitochondrial Morphology and Metabolic Changes in Retinal Pericytes

Mitochondrial dysfunction is known to play a role in retinal vascular cell loss, a prominent lesion of diabetic retinopathy. High glucose (HG) has been reported to induce mitochondrial fragmentation and dysfunction in retinal endothelial cells, contributing to apoptosis. In this study, the effects of HG on mitochondrial morphology, membrane potential, and metabolic changes and whether they could contribute to HG-induced apoptosis in retinal pericytes were investigated. Bovine retinal pericytes (BRPs) were grown in normal or HG medium for 7 days. Both sets of cells were double stained with mitochondrial membrane potential-independent dye and tetramethylrhodamine-ethyl-ester-perchlorate (TMRE) and imaged by confocal microscopy. The images were analyzed for average mitochondria shape, by using form factor and aspect ratio values, and membrane potential changes, by using the ratio between the red and green dye. BRPs grown in normal or HG medium were analyzed for transient changes in oxygen consumption and extracellular acidification with a flux analyzer and apoptosis by TUNEL assay. BRPs grown in HG media exhibited significant fragmentation of mitochondria and increased membrane potential heterogeneity compared with the BRPs grown in normal medium. Concomitantly, BRPs grown in HG showed reduced steady state and maximum oxygen consumption and reduced extracellular acidification. Number of TUNEL-positive pericytes was increased in HG condition as well. In HG condition, mitochondria of retinal pericytes display significant fragmentation, metabolic dysfunction, and reduced extracellular acidification. The detrimental effects of HG on mitochondrial function and cellular metabolism could play a role in the accelerated apoptosis associated with the retinal pericytes in diabetic retinopathy.

Use of a modified form factor to compare condition among North American lake sturgeon stocks

Summary In fisheries management it is often useful to compare length and weight relationships or condition among populations across a species’ range. Currently, the most commonly used metric for this is relative weight (Wr), although some problems have arisen with the use of Wr including the impact of seasonal changes in body condition due to reproduction, and length-related biases in standard weight equations. We propose the use of a modified form factor (mFF) based on the regression of log10α vs β (weight–length model parameters) within a species, to provide a quick and meaningful comparison of mean condition among North American lake sturgeon populations. We used the α and β parameters from 63 lake sturgeon weight–length models from 43 lake sturgeon populations from throughout their range in the equation to calculate the mFF for the 63 samples. Modified form factor values of juvenile, adult male, and female lake sturgeon from the Winnebago System, Wisconsin, in various stages of reproductive development had a 98.0% correlation with their respective relative condition values over a wide range of mFF values. Simple t-tests on sets of mFF values can be used to test the condition differences between populations or sub-samples within populations. Lake sturgeon from the Winnebago System, Wisconsin, USA were found to show W–L relationships best described in two stanzas: all juveniles 71 cm) W–L models; juvenile (≤71 cm) and male (>71 cm) models; and juvenile (≤71 cm) and female (>71 cm) models.

Derivation of two-way volume equation for bamboo, Phyllostachys pubescens

We derive a two-way volume equation for estimating the apparent culm volume of one of the largest bamboo species, Phyllostachys pubescens Mazel ex Houz. The volume equation was derived from the assumptions that (1) the relative culm form can be expressed by Kunze's equation and (2) normal form-factors at two different relative heights are steady at constants independent of culm sizes. A total number of 200 sample culms were collected from a stand of P. pubescens in Mt. Toshima, Kumamoto Prefecture, western Japan, and were randomly bisected into two sets of data, i.e. modeling and test data. For the modeling data, normal form-factors at 0.6 and 0.9 in relative height were steady at 0.908 and 0.448, respectively. The coefficients of the volume equation were determined based on these steady values of the normal form-factors. For the test data, the apparent culm volume was estimated from diameter at breast height and culm height with the determined volume equation. The mean error and root mean square error of the estimated culm volume were, respectively, 8.120 × 10−5 and 3.291 × 10−3 m3, and there was no significant difference between estimated and actual volume. In conclusion, the two-way volume equation presented here appears to be convenient for predicting the apparent culm volume for P. pubescens.

Analysis of theD+→K−π+e+νedecay channel

Using 347.5 fb-1 of data recorded by the BABAR detector at the PEP-II electron-positron collider, 244*10^3 signal events for the D+ --> K- pi+ e+ nu_e decay channel are analyzed. This decay mode is dominated by the \bar{K}^*(892)^0 contribution. We determine the \bar{K}^*(892)^0 parameters: m_{K^*(892)^0}=(895.4 +- 0.2 +- 0.2) MeV/c^{2}, \Gamma^0_{K^*(892)^0}=(46.5 +- 0.3 +- 0.2) MeV/c^{2} and the Blatt-Weisskopf parameter $r_{BW}=2.1 +- 0.5 +- 0.5 (GeV/c)^{-1} where the first uncertainty comes from statistics and the second from systematic uncertainties. We also measure the parameters defining the corresponding hadronic form factors at q^{2}=0 (r_{V} = V(0) / A_{1}(0)=1.463 +- 0.017 +- 0.031, r_{2} = A_{2}(0) / A_{1}(0) = 0.801 +- 0.020 +- 0.020) and the value of the axial-vector pole mass parameterizing the q^2 variation of A_{1} and A_{2}: m_{A}=(2.63 +- 0.10 +- 0.13) GeV/c^{2}. The S-wave fraction is equal to (5.79 +- 0.16 +- 0.15)%. Other signal components correspond to fractions below 1%. Using the D+ --> K- pi+ pi+ channel as a normalization, we measure the D+ semileptonic branching fraction: BR(D+ --> K- pi+ e+ nu_e) = (4.04 +- 0.03 +- 0.04 +- 0.09) \times 10^{-2} where the third uncertainty comes from external inputs. We then obtain the value of the hadronic form factor A_1 at q^{2}=0: A_{1}(0) = 0.6226 +- 0.0056 +- 0.0065 +- 0.0074. Fixing the P-wave parameters we measure the phase of the S-wave for several values of the Kpi mass. These results confirm those obtained with Kpi production at small momentum transfer in fixed target experiments.

Fractionation and Characterization of Particles Simulating Wear of Total Joint Replacement (TJR) Following ASTM Standards

Reactions of bone cells to orthopedic wear debris produced by the articulating motion of total joint replacements (TJRs) are largely responsible for the long-term failure of such replacements. Metal and polyethylene (PE) wear particles isolated from fluids from total joint simulators, as well as particles that are fabricated by other methods, are widely used to study such in vitro cellular response. Prior investigations have revealed that cellular response to wear debris depends on the size, shape, and dose of the particles. Hence, to have a better understanding of the wear-mediated osteolytic process it is important that these particles are well characterized and clinically relevant, both qualitatively, and quantitatively. In this study we have fractionated both ultra-high molecular weight polyethylene (UHMWPE) and Ti particles, into micron (1.0-10.0 μm), submicron (0.2-1.0 μm), and nanoparticle (0.01-0.2 μm) fractions, and characterized them based on the following size-shape descriptors as put forth in ASTM F1877: i) equivalent circle diameter (ECD), ii) aspect ratio (AR), iii) elongation (E), iv) roundness (R), and v) form factor (FF). The mean (± SD) ECDs (in μm) for micron, submicron, and nanoparticles of UHMWPE were 1.652 ± 0.553, 0.270 ± 0.180, and 0.061 ± 0.035, respectively, and for Ti were 1.894 ± 0.667, 0.278 ± 0.180, and 0.055 ± 0.029, respectively. The values for other descriptors were similar (no statistically significant difference). The nanofraction particles were found to be more sphere-like (higher R and FF values, and lower E and AR values) as compared to larger particles. Future experiments will involve use of these well characterized particles for in vitro studies.

High Glucose Disrupts Mitochondrial Morphology in Retinal Endothelial Cells: Implications for Diabetic Retinopathy

Mitochondrial dysfunction has been implicated in diabetic complications; however, it is unknown whether hyperglycemia affects mitochondrial morphology and metabolic capacity during development of diabetic retinopathy. We investigated high glucose (HG) effects on mitochondrial morphology, membrane potential heterogeneity, cellular oxygen consumption, extracellular acidification, cytochrome c release, and apoptosis in retinal endothelial cells. Rat retinal endothelial cells grown in normal (5 mmol/L) or HG (30 mmol/L) medium and double-stained with MitoTracker Green and tetramethylrhodamine-ethyl-ester-perchlorate were examined live with confocal microscopy. Images were analyzed for mitochondrial shape change using Form Factor and Aspect Ratio values, and membrane potential heterogeneity, using deviation of fluorescence intensity values. Rat retinal endothelial cells grown in normal or HG medium were analyzed for transient changes in oxygen consumption and extracellular acidification using an XF-24 flux analyzer, cytochrome c release by Western blot, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Rat retinal endothelial cells grown in HG medium exhibited increased mitochondrial fragmentation concurrent with membrane potential heterogeneity. Metabolic analysis showed increased extracellular acidification in HG with reduced steady state/maximal oxygen consumption. Cytochrome c and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells were also increased in HG. Thus, HG-induced mitochondrial fragmentation with concomitant increase in membrane potential heterogeneity, reduced oxygen consumption, and cytochrome c release may underlie apoptosis of retinal endothelial cells as seen in diabetic retinopathy.

Chiral extrapolation of the strangeness changing scalar Kπ form factor

We perform a chiral extrapolation of lattice data on the scalar Kπ form factor and the ratio of the kaon and pion decay constants within Chiral Perturbation Theory to two loops. We determine the value of the scalar form factor at zero momentum transfer, at the Callan-Treiman point and at its soft kaon analog as well as its slope. Results are in good agreement with their determination from experiment using the standard couplings of quarks to the W boson. The slope is however rather large. A study of the convergence of the chiral expansion is also performed.

Two-boson exchange corrections to parity-violating elastic electron-proton scattering

Details of the calculation of two-boson exchange effects in parity-violating elastic $\mathit{ep}$ scattering within a simple hadronic model, including both the nucleon and the $\ensuremath{\Delta}(1232)$-resonance intermediate states, are presented. We examine the sensitivity of our results with respect to choice of form factors. We emphasize the importance of using correct relations relating $N\ensuremath{\rightarrow}\ensuremath{\Delta}$ and $\ensuremath{\Delta}\ensuremath{\rightarrow}N$ transition vertex functions. The $N\ensuremath{\Delta}$ Coulomb quadrupole transition is found to play an important role at higher ${Q}^{2}\ensuremath{\geqslant}3.0$ GeV${}^{2}$. We also elucidate the relation between our results and the well-known result on the $\ensuremath{\gamma}Z$-boson exchange effect given by Marciano and Sirlin. The effect of the nucleon contribution ${\ensuremath{\delta}}_{N}$ to parity asymmetry ${A}_{\mathrm{PV}}$ is found to be, in general, larger than the corresponding $\ensuremath{\Delta}$ contribution ${\ensuremath{\delta}}_{\ensuremath{\Delta}}$ except at extreme forward angles. Corrections to the extracted values of the strange form factors ${G}_{E}^{s}+\ensuremath{\beta}{G}_{M}^{s}$ from the HAPPEX, A4, and G0 data are also presented. The total TBE corrections to the extracted values of ${G}_{E}^{s}+\ensuremath{\beta}{G}_{M}^{s}$ in recent HAPPEX, G0, and A4 experiments are, depending on kinematics, found to be small except in a few cases where they range from $\ensuremath{-}20.6%$ to $48.3%$.

Dispersive analysis ofKLμ3andKLe3scalar and vector form factors using KTeV data

Using the published KTeV samples of K_L --> pi^{\pm} e^{\mp} nu and K_L --> pi^{\pm} mu^{\mp} nu decays [1], we perform a reanalysis of the scalar and vector form factors based on the dispersive parameterization [2,3]. We obtain phase space integrals I^e_K = 0.15446 \pm 0.00025 and I^{mu}_K = 0.10219 \pm 0.00025. For the scalar form factor parameterization, the only free parameter is the normalized form factor value at the Callan-Treiman point (C); our best fit results in ln C = 0.1915 \pm 0.0122. We also study the sensitivity of C to different parametrizations of the vector form factor. The results for the phase space integrals and C are then used to make tests of the Standard Model. Finally, we compare our results with lattice QCD calculations of F_K/F_pi and f_+(0).

Dendrometric and dasometric analysis of the bushy biomass in Mediterranean forests

Abstract The aim of this study was to define the dendrometric and dasometric parameters of five Mediterranean bushy plant species, to make their environmental assessment and to determine correlations with LIDAR data. The species studied were: Quercus coccifera, Rosmarinus officinalis, Ulex parviflorus, Cistus albidus, and Erica multiflora. We calculated the global form factor for each species so as to be able to determine the volume of the plants by measuring their base diameter and length. The model volume closest to the real volume was the cylinder, which had form factor values of between 0.8 and 2.33. We also studied the evolution of the moisture content of the vegetation after cutting. The initial values were from 20 to 30%, with a dry density of 1 t/m3. We defined an occupation factor to determine the relationship between the real volume occupied by the plants in an area and a model volume (hemisphere, paraboloid, cone, and cylinder). The occupation factor was similar for the five species studied in dm3 of material per m3 of (model) apparent volume: 3.5 dm3/m3 for the cylinder; 12.5 dm3/m3 for the cone; 8.5 dm3/m3 for the paraboloid; and 14.5 dm3/m3 for the hemisphere. These factors enabled us to calculate the biomass contained in an apparent volume of bushes (including materials and hollows) by density. The prediction models tested in this study will thus serve to determine the biomass of a bushy forest area when the Canopy Height Model (CHM) is calculated from LIDAR data.

Covariant nonlocal chiral quark model and pion-photon transition distribution amplitudes

Using a nonlocal chiral quark model with simple pole ansatz for the momentum dependence of the constituent quark mass and nonlocal currents satisfying Ward-Takahashi identities, we calculate pion-to-photon transition distribution amplitudes and relevant form factors. For vector amplitude we recover correct normalization fixed by the axial anomaly. We find that due to the nonlocality in the vector current, the value of the axial form factor at zero momentum transfer is lowered with respect to the vector form factor. Such behavior---consistent with experiment---is not seen in the local models. Where possible we compare our results to the experimental data.

New Precise Measurement of the Pion Weak Form Factors inπ+→e+νγDecay

We have measured the π+→e+νγ branching ratio over a wide region of phase space, based on a total of 65 460 events acquired using the PIBETA detector. Minimum-χ2 fits to the measured (Ee+, Eγ) energy distributions result in the weak form factor value of FA=0.0119(1) with a fixed value of FV=0.0259. An unconstrained fit yields FV=0.0258(17) and FA=0.0117(17). In addition, we have measured a=0.10(6) for the dependence of FV on q2, the e+ν pair invariant mass squared, parametrized as FV(q2)=FV(0)(1+aq2). The branching ratio for the kinematic region Eγ>10 MeV and θe+γ>40° is measured to be Bexpt=73.86(54)×10−8. Earlier deviations we reported in the high-Eγ–low-Ee+ kinematic region are resolved without a tensor term. We also derive new values for the pion polarizability αE=2.78(10)×10−4 fm3 and neutral pion lifetime τπ0=(8.5±1.1)×10−17 s.Received 15 April 2008DOI:https://doi.org/10.1103/PhysRevLett.103.051802©2009 American Physical Society

Effects of electronic state modulation on the high-frequency response characteristics of GaAs quantum wells

Abstract The effect of electronic-state modulation on the high frequency response of GaAs quantum well with thin inserted barrier layer is studied. The carrier scattering by polar optic phonons, acoustic deformation potential and background ionized impurities are incorporated in the present calculations considering the carrier distribution to be heated drifted Fermi–Dirac distribution. Modified phonon spectra and modulated electron wave function give different values of form factor compared to bulk mode phonon. Mobility is found to be enhanced on insertion of thin layer inside the quantum well. The ac mobility and the phase lag increases with the increase in both the channel width and the 2D carrier concentration. Cutoff frequency, where ac mobility drops down to 0.707 of its low frequency value, is observed to be enhanced reflecting better high frequency response.

SemileptonicBcto P-wave charmonia transitions within QCD sum rules

The form factors of the semileptonic ${B}_{c}\ensuremath{\rightarrow}S(AV)\ensuremath{\ell}\ensuremath{\nu}$ ($\ensuremath{\ell}=\ensuremath{\tau}$, $\ensuremath{\mu}$, $e$) transitions, where $S$ and $AV$ denote the scalar ${X}_{c0}$ and axial-vector $({X}_{c1},{h}_{c})$ mesons, are calculated within the framework of the three-point QCD sum rules. The heavy quark effective theory limit of the form factors is also obtained and compared with the values of the original transition form factors. The results of form factors are used to estimate the total decay widths and branching ratios of these transitions. A comparison of our results on branching ratios with the predictions of other approaches is also presented.

Construction of Lorentz-Invariant Amplitudes from Rest-Frame Wave Functions in HQET: Application to the Isgur-Wise Function

Succeeding in predicting 0^+ and 1^+ states of D and D_s heavy mesons by our semi-relativistic quark potential model, we examine a method how to construct Lorentz-invariant scattering amplitudes and/or decay widths and develop a formulation to calculate Lorentz-boosted ones given the rest frame wave functions in our model. To show how effective this is, we apply the formulation to calculate the semileptonic weak form factors out of the rest frame wave functions of heavy mesons and numerically calculate the dynamical 1/m_Q corrections to those for the process B-bar -> D^{(*)}\ell\nu based on our model for heavy mesons. It is shown that nonvanishing expressions for \rho_1(\omega)=\rho_2(\omega) and \rho_3(\omega)=\rho_4(\omega)=0 are obtained in a special Lorentz frame, where \rho_i(\omega) are the parameters used in the Neubert-Rieckert decomposition of form factors. Various values of form factors are estimated, which are compatible with recent experimental data as well as other theoretical calculations.

Electromagnetic form factor of the pion from twisted-mass lattice QCD atNf=2

We present a lattice calculation of the electromagnetic form factor of the pion obtained using the tree-level Symanzik improved gauge action with two flavors of dynamical twisted Wilson quarks. The simulated pion masses range approximately from 260 to 580 MeV, and the lattice box sizes are chosen in order to guarantee that ${M}_{\ensuremath{\pi}}L\ensuremath{\gtrsim}4$. Accurate results for the form factor are obtained using all-to-all quark propagators evaluated by a stochastic procedure. The momentum dependence of the pion form factor is investigated up to values of the squared four-momentum transfer ${Q}^{2}\ensuremath{\simeq}0.8\text{ }\text{ }{\mathrm{GeV}}^{2}$ and, thanks to the use of twisted boundary conditions, down to ${Q}^{2}\ensuremath{\simeq}0.05\text{ }\text{ }{\mathrm{GeV}}^{2}$. Volume and discretization effects on the form factor appear to be within the statistical errors. Our results for the pion mass, decay constant and form factor are analyzed using (continuum) chiral perturbation theory at next-to-next-to-leading order. The extrapolated value of the pion charge radius is $⟨{r}^{2}{⟩}^{\mathrm{phys}}=0.456\ifmmode\pm\else\textpm\fi{}{0.030}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.024}_{\mathrm{syst}}$ in nice agreement with the experimental result. The extrapolated values of the pion form factor agree very well with the experimental data up to ${Q}^{2}\ensuremath{\simeq}0.8\text{ }\text{ }{\mathrm{GeV}}^{2}$ within uncertainties which become competitive with the experimental errors for ${Q}^{2}\ensuremath{\gtrsim}0.3\text{ }\text{ }{\mathrm{GeV}}^{2}$. The relevant low-energy constants appearing in the chiral expansion of the pion form factor are extracted from our lattice data, which come essentially from a single lattice spacing, adding the experimental value of the pion scalar radius in the fitting procedure. Our findings are in nice agreement with the available results of chiral perturbation theory analyses of $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ scattering data as well as with other analyses of our collaboration.

FUZZY C-MEANS CLUSTERING FOR MYOCARDIAL ISCHEMIA ESTIMATION WITH PULSE WAVEFORM ANALYSIS

The purpose of this study is to build an automatic disease classification algorithm by pulse waveform analysis, based on a Fuzzy C-means clustering algorithm. A self designed three-axis mechanism was used to detect the optimal position to accurately measure the pressure pulse waveform (PPW). Considering the artery as a cylinder, the sensor should detect the PPW with the lowest possible distortion, and hence an analysis of the vascular geometry and an arterial model were used to design a standard positioning procedure based on the arterial diameter changed waveform for the X-axes (perpendicular to the forearm) and Z-axes (perpendicular to the radial artery). A fuzzy C-means algorithm was used to estimate the myocardial ischemia symptoms in 35 elderly subjects with the PPW of the radial artery. Two type parameters were used to make the features, one was a harmonic value of Fourier transfer, and the other was a form factor value. A receiver operating characteristics curve was used to determine the optimal decision function. The harmonic feature vector contain second, third and fourth harmonics ( H 2, H 3, H 4) performed at the level of 69% for sensitivity and 100% for specificity while the form factor feature vector derived from left hand (LFF) and right hand (RFF) performed at the level of 100% for sensitivity and 53% for specificity. The FCM- and ROC-based clustering approach may become an efficient alternative for distinguishing patients in the risk of myocardial ischemia, besides the traditional exercise ECG examination.

Morphometry using remote sensing and GIS techniques in the sub-basins of Kagna river basin, Gulburga district, Karnataka, India

The study area is a part of Kagna river basin in the Gulburga district of Karnataka, India. It covers an area of 1320 km2 and it has been subdivided into 4 sub-basins namely Wadi, Chitapur, Sedam and Kurkunta, which range in area from 184 to 537 km2. The drainage pattern of these sub-basins are delineated using Geo-coded FCC bands 2,3,4 of IRS 1C and 1D(LISS III+PAN merged) on 1:50,000 scale and Survey of India toposheets as reference. The morphometric parameters are computed using ArcInfo and ArcView GIS softwares. The drainage pattern of the study area is dendritic to sub-dendritic with stream orders ranging from IV to VII orders. Drainage density ranges from 1.40 to 1.86 km/km2 suggesting coarse to moderate drainage texture. The change in values of stream length ratio indicate their late youth stage of geomorphic development. The values of bifurcation ratio ranging from 2.00 to 4.71 indicate that all the sub-basins fall under normal basin category. The values of form factor and circulatory ratio, suggest that the Kurkunta sub-basin is elongated and the remaining sub-basins are more or less circular in shape. Elongation ratio indicates that the Wadi sub-basin is a region of very low relief whereas the other sub-basins are associated with moderate to high relief and steep ground slopes. It is concluded that remote sensing and GIS have been proved to be efficient tools in drainage delineation and updation. In the present study these updated drainages have been used for the morphometric analysis.

Gravitational and higher-order form factors of the pion in chiral quark models

The gravitational form factor of the pion is evaluated in two chiral quark models and confronted with the recent full-QCD lattice data. We find good agreement for the case of the spectral quark model, which builds in the vector-meson dominance for the charge form factor. We derive a simple relation between the gravitational and electromagnetic form factors, holding in the considered quark models in the chiral limit. The relation implies that the gravitational mean squared radius is half the electromagnetic one. We also analyze higher-order quark generalized form factors of the pion, related to higher moments in the symmetric Bjorken X variable of the generalized parton distribution functions, and discuss their perturbative QCD evolution, which is needed to relate the quark-model predictions to the lattice data. The values of the higher-order quark form factors at t=0, computed on the lattice, also agree with our quark-model results within the statistical and method uncertainties.