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BACKGROUND: Length of stay and functional outcomes after total knee arthroplasty (TKA) are related to the timing and intensity of post-operative rehabilitation. OBJECTIVE: To determine the effectiveness of early and high-intensity rehabilitation after simultaneous bilateral TKA. METHODS: Prospective cohort data of 156 patients (11 men and 145 women; average age 72.0 ± 5.6 years) who underwent simultaneous bilateral primary TKA were analyzed. The intervention group (n= 82) underwent a high-intensity rehabilitation (phase II) after early postoperative standard rehabilitation (phase I) between June 2019 and May 2021. The control group (n= 74) underwent a lower-intensity rehabilitation (phase II) after phase I rehabilitation between July 2017 and May 2019. The timed up-and-go (TUG) test, timed stair climbing test (SCT), 6-minute walk test, isometric knee extensor and flexor strength of both knees, knee flexion and extension range of motion, Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) for pain, stiffness, and functional levels, and the EuroQol five-dimension questionnaire were assessed preoperatively and 6 weeks after TKA. RESULTS: The average length of hospital stay was shortened by 5.7 days (p< 0.001). Phase II rehabilitation started earlier in the intervention group than in the control group (7.7 ± 1.3 vs 13.5 ± 2.0, p< 0.001). Compared with the control group, the intervention group showed significant improvements in the measures of mobility (WOMAC-function and SCT) and strength (isometric strength of both knee extensors and flexors) 6 weeks after TKA by statistically controlling for age and preoperative functional status. CONCLUSION: This study demonstrated that early and high-intensity rehabilitation could achieve functional improvement and shorten the length of hospital stay.

Background Although total knee arthroplasty (TKA) is an effective treatment for knee osteoarthritis, assessment of postoperative outcomes remains unclear. This study aimed to identify postoperative physical performance factors that are correlated with self-reported physical function and quality of life (QoL) at 3 months after unilateral TKA. Methods In total, 158 patients who underwent unilateral primary TKA completed performance-based physical function tests at 3 months after surgery, including Stair Climbing Tests (SCT), 6-Minute Walk Tests (6MWT), Timed Up and Go tests (TUG), and instrumental gait analysis. We also measured the isometric knee flexor and extensor strengths of the operated and non-operated knees. Self-reported physical function and QoL were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Euro-QoL Five Dimensions (EQ-5D) questionnaire, respectively. Results Bivariate analyses showed that WOMAC function and EQ-5D were correlated with age, other self-reported measures, and performance-based measures. The WOMAC pain (r=0.71, p

We aimed to investigate the prevalence of osteoporosis and low lean mass, either together or in isolation, and their association with physical function, pain, and quality of life (QOL) in patients with end-stage knee osteoarthritis (OA). This retrospective cross-sectional observational study included 578 patients (77 males and 501 females) diagnosed with end-stage knee OA. Patients were divided into 4 groups based on body composition parameters: control, osteoporosis, low lean mass, and osteoporosis + low lean mass. All participants underwent performance-based physical function tests, including a stair climbing test (SCT), a 6-minute walk test, a timed up and go test, and instrumental gait analysis, to examine spatiotemporal parameters. Self-reported physical function and pain levels were measured using the Western Ontario McMaster Universities Osteoarthritis Index and visual analog scale, respectively. Self-reported QOL was measured using the EuroQOL 5 dimensions (EQ-5D) questionnaire. Of 578 patients, 268 (46.4%) were included in the control group, 148 (25.6%) in the osteoporosis group, 106 (18.3%) in the low lean mass group, and 56 (9.7%) in the osteoporosis + low lean mass group. Analysis of variance revealed that the scores for the osteoporosis + low lean mass group in the SCT-ascent, SCT-descent, and timed up and go test were significantly higher, whereas those for the 6-minute walk test, gait speed, and cadence were significantly lower than those for the other groups (P.05). After adjusting for age, sex, and body mass index, multiple linear regression analysis identified SCT-ascent (β = 0.140, P = .001, R2 = 0.126), SCT-descent (β = 0.182, P.001, R2 = 0.124), gait speed (β = -0.116, P = .005, R2 = 0.079), and cadence (β = -0.093, P = .026, R2 = 0.031) as being significantly associated with osteoporosis + low lean mass. Thus, osteoporosis + low lean mass correlates with poor physical function, but not pain and QOL, in patients with end-stage knee OA.

Objective: To investigate the prevalence of obesity with low muscle mass and its impact on physical function, quality of life (QOL) and pain in patients with end-stage knee osteoarthritis over 65 years old. Methods: In this cross-sectional study, we assessed a total of 562 patients. After separating the group into males and females, we divided patients into 4 further groups: normal BMI with normal muscle mass, obesity with normal muscle mass, normal BMI with low muscle mass and obesity with low muscle mass. All patients completed stair climbing test (SCT), 6-minute walk test, timed up and go test (TUG), instrumental gait analysis, Western Ontario McMaster Universities Osteoarthritis Index, VAS, and EuroQOL 5 dimensions questionnaire. Results: Obesity with low muscle mass was diagnosed in 6 males subjects (7.8%) and 9 female subjects (1.9%). Patients with obesity and low muscle mass performed the SCT-ascent and descent significantly slower than other body composition groups in both males and females. TUG in males and gait speed in females were also significantly slower in the obesity with low muscle mass group. Stepwise multiple linear regression analysis revealed that in males, obesity with low muscle mass was significantly predictive of SCT ascent (β = 0.409, p < 0.001), SCT-descent (β = 0.405, p < 0.001), and TUG (β = 0.283, p = 0.009), and in females, obesity with low muscle mass was significantly predictive of SCT-ascent (β = 0.231, p < 0.001), SCT-descent (β = 0.183, p < 0.001), and gait speed (β=-0.129, p = 0.004). Conclusions: This study confirms that the combination of obesity and low muscle mass is associated with impaired physical function in patients with end-stage knee osteoarthritis.

OBJECTIVE The aim of the study was to determine the effect of comorbidities on physical function and quality of life of patients at 3 mos after total knee arthroplasty. DESIGN Data from 140 patients who underwent a primary unilateral total knee arthroplasty were examined retrospectively. Comorbidities were osteoporosis, presarcopenia, degenerative spine disease, diabetes, and hypertension. All patients completed the following: range of motion, stair climbing test, 6-min walk test, Timed Up and Go Test, peak torque of the knee extensor and flexor, instrumental gait analysis, Western Ontario McMaster Universities Osteoarthritis Index, and EuroQoL five-dimension questionnaire. RESULTS Univariate analyses revealed that osteoporosis led to a significantly longer time to complete the stair climbing test-ascent, stair climbing test-descent, and Timed Up and Go Test and to lower scores for the 6-min walk test and peak torque of the knee extensor. Patients with degenerative spine disease showed significant negative scores for knee extension range of motion. Diabetes showed a negative correlation with peak torque of the knee extensor and knee flexion range of motion, as well as a higher Western Ontario McMaster Universities Osteoarthritis Index-stiffness score. Multivariable linear regression analysis showed that Western Ontario McMaster Universities Osteoarthritis Index-stiffness remained independently associated with diabetes. Six-minute walk test, Timed Up and Go Test, stair climbing test-ascent, and peak torque of the knee extensors showed a significant association with osteoporosis. CONCLUSIONS Comorbidities, particularly osteoporosis and diabetes, affect short-term functional outcomes 3 mos after total knee arthroplasty.

Background: The purpose of this study was to investigate the effectiveness of a home-based fragility fracture integrated rehabilitation management (H-FIRM) program following an inpatient FIRM (I-FIRM) program in patients surgically treated for hip fracture. Methods: This nonrandomized controlled trial included 32 patients who underwent hip surgery for a fragility hip fracture. The patients were divided into two groups: a prospective intervention group (n = 16) and a historical control group (n = 16). The intervention group performed a nine-week H-FIRM program combined with the I-FIRM program. The historical control group performed the I-FIRM program only. Functional outcomes included Koval&rsquo, s grade, Functional Ambulatory Category (FAC), Functional Independence Measure (FIM) locomotion, Modified Rivermead Mobility Index (MRMI), 4 m walking speed test (4MWT), and the Korean version of Modified Barthel Index (K-MBI). All functional outcomes were assessed one week (before I-FIRM), three weeks (before I-FIRM), and three months (after H-FIRM) after surgery. Results: Both groups showed significant and clinically meaningful improvements in functional outcomes over time. Compared with the control group, the intervention group showed clinically meaningful improvements in Koval&rsquo, s grade, FAC, FIM locomotion, MRMI, 4MWT, and K-MBI from baseline to three months. Conclusion: H-FIRM may be an effective intervention for improving functional outcomes in older people after fragility hip fractures.

Background After total knee arthroplasty (TKA), walking speed and distance are main concerns of patients. Research question Which physical functions affect walking speed and distance after TKA? Methods Cross-sectional data from 149 patients who underwent unilateral primary TKA and completed performance-based physical function tests. Instrumental gait evaluation for spatiotemporal parameters, isometric knee extensor and flexor strength of both knees, 6-minute walk test (6MWT), timed up-and-go (TUG) test, timed stair climbing test (SCT), and knee flexion and extension range of motion (ROM) of surgical knee were examined. Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and EuroQol five dimensions (EQ-5D) questionnaires were also performed. Results Univariate analyses revealed that post-operative walking speed showed significant positive correlations with cadence, stride length, propulsion index of surgical and non-surgical knee, peak torque (PT) of the extensor of surgical and non-surgical knee and flexor of surgical and non-surgical knee, 6MWT, EQ-5D, and significant negative correlations with gait cycle duration, TUG, SCT-ascent and descent, and WOMAC-pain scores. Post-operative walking distance had significant positive correlations with walking speed, cadence, stride length, swing phase duration, propulsion index of surgical and non-surgical knee, PT of the extensor of surgical and non-surgical knee, EQ-5D, and significant negative correlation with gait cycle duration, double support duration, TUG, SCT-ascent and descent. In the multivariate linear regression analyses, TUG, cadence, stride length and propulsion index of non-surgical knee were factor correlated with post-operative walking speed. The SCT-ascent and descent, TUG and propulsion index of surgical knee were factor correlated with post-operative walking distance. Significance Physical performance factors correlated with walking speed and distance at 3 months after surgery. Based on these observations, rehabilitation of bilateral muscle strength and functional mobility would be important for functional recovery after unilateral TKA.

Background and objectives: Aquatic exercises have demonstrated several advantages over land-based exercise, but only a few studies have compared the workout intensities and efficiencies in a stage-specific manner. This study aimed to investigate workout intensity during aquatic and land-based running, based on the rating of perceived exertion (RPE). Materials and Methods: Twenty healthy young male subjects underwent a land-based running test (LRT) and an aquatic running test (ART), in the form of a cardiopulmonary exercise treadmill test and a shallow-water running test. The seven stages of the ART were composed of 3 minutes each of the Bruce protocol performed during the LRT. In the ART, the participants were instructed to run in a swimming pool with matching RPE to that obtained at each stage of the LRT. Results: Heart rate (HR) during both LRT and ART exhibited a linear relationship (r = 0.997 and 0.996, respectively, p &lt, 0.001). During the initial and middle period, HR was higher in the ART than in the LRT. However, in the final period, HR was higher in the LRT than in the ART. Conclusions: In aquatic exercises based on the RPE obtained from the LRT, HR exhibited a linear relationship in both the ART and the LRT. The ART appears to increase cardiac loading more efficiently in the initial period and does not increase cardiac loading abruptly at a later period. Although there is no precise, objective, controlled parameter to compare the ART and the LRT, the RPE may be used as a convenient measurement for workout intensity in aquatic running.

The reactions of [Pt(styrene)(PMe3)2] with 2 equiv. of alkyl or aryl isocyanate affored five-membered platinacycles, cis-[Pt{–N(R)C(O)N(R)C(O)–}(PMe3)2] (R = CH2C6H5, p-ClC6H4, p-OMeC6H4). These complexes are the first examples of platinacycles containing an isocyanate dimer unit. When the five-membered bis(phosphine) platinacycles or palladacycles were treated with 2 equiv. of elemental sulfur, 16-membered cyclic products as an assembly of four platinacycles or palladacycles, [M(PR3){–N(R)C(O)N(R)C(O)–}]4, were readily obtained. These cyclic tetramers were cleaved using tert-butyl isocyanide (CN–tbutyl, 4 equiv.), affording the corresponding monomeric complexes, [M(PR3)(CN–tbutyl){–N(R)C(O)N(R)C(O)–}] (M = Pt, Pd). An unusual cyclotrimerization of organic isocyanates catalyzed by zerovalent Pt complexes or five-membered platinacycles was observed. In addition, the direct cyclotrimerization of alkyl or aryl isocyanates using dialkyl Pt(II) or Pd(II) complexes was investigated. The cross cyclotrimerization of an aryl isocyanate and its derivative using a zerovalent Pd complex was also investigated.

Photoheating associated with reionization suppressed star formation in low-mass galaxies. Reionization was inhomogeneous, however, affecting different regions at different times. To establish the causal connection between reionization and suppression, we must take this local variation into account. We analyze the results of CoDa (`Cosmic Dawn') I, the first fully-coupled radiation-hydrodynamical simulation of reionization and galaxy formation in the Local Universe, in a volume large enough to model reionization globally but with enough resolving power to follow all atomic-cooling galactic halos in that volume. For every halo identified at a given time, we find the redshift at which the surrounding IGM reionized, along with its instantaneous star formation rate (`SFR') and baryonic gas-to-dark matter ratio ($M_\text{gas}/M_\text{DM}$). The average SFR per halo with $M < 10^9 \text{ M}_\odot$ was steady in regions not yet reionized, but declined sharply following local reionization. For $M > 10^{10} \text{ M}_\odot$, this SFR continued through local reionization, increasing with time, instead. For $10^9 < M < 10^{10} \text{ M}_\odot$, the SFR generally increased modestly through reionization, followed by a modest decline. In general, halo SFRs were higher for regions that reionized earlier. A similar pattern was found for $M_\text{gas}/M_\text{DM}$, which declined sharply following local reionization for $M < 10^9 \text{ M}_\odot$. Local reionization time correlates with local matter overdensity, which determines the local rates of structure formation and ionizing photon consumption. The earliest patches to develop structure and reionize ultimately produced more stars than they needed to finish and maintain their own reionization, exporting their `surplus' starlight to help reionize regions that developed structure later., 15 pages, 15 figures, accepted by MNRAS 07/17/18, comments welcome

We study the early stage of the formation of seed supermassive black holes via direct collapse in dark matter (DM) halos, in the cosmological context. We perform high-resolution zoom-in simulations of such collapse at high-$z$. Using the adaptive mesh refinement code ENZO, we resolve the formation and growth of a DM halo, until its virial temperature reaches $\sim 10^4$K, atomic cooling turns on, and collapse ensues. We demonstrate that direct collapse proceeds in two stages, although they are not well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing accretion rate with radius, from $\dot M\sim 0.1\,M_\odot {\rm yr^{-1}}$ at the halo virial radius to few $M_\odot \,{\rm yr^{-1}}$, around the scale radius $R_{\rm s}\sim 30$pc of the NFW DM density profile. The second stage of the collapse commences when the gas density takes precedence over the DM density. This is associated with the gas decoupling from the DM gravitational potential. The ensuing collapse approximates that of an isothermal sphere with $\dot M ( r )\sim $const. We confirm that the gas loses its angular momentum through non-axisymmetric perturbations and gravitational torques, to overcome the centrifugal barrier. During the course of the collapse, this angular momentum transfer process happens on nearly all spatial scales, and the angular momentum vector of the gas varies with position and time. Collapsing gas also exhibits supersonic turbulent motions which suppress gas fragmentation, and are characterized by density PDF consisting of a lognormal part and a high-density power law tail.

Objective To investigate the effect of dual-task training on the recovery of balance ability and cognitive function in patients with subacute stroke. Methods Twenty patients (12 males and eight females; average age, 59.70 years) with subacute stroke were enrolled in this study. All participants were randomly assigned to one of two groups, the dual-task group (n=10) or the control group (n=10). The dual task was simultaneous balance and cognitive training using the BioRescue. All patients were evaluated with posturographic parameters and the Berg Balance Scale for balance ability, a computerized neuropsychological test and the Korean version of the Mini-Mental State Examination for cognitive function, the Fugl-Meyer Assessment for motor function, and the Korean-Modified Barthel Index for activities of daily living (ADL) function before and after 4 weeks of rehabilitation. Results The dual-task group showed significant improvements in the pressure of the weight distribution index (WDI), surface area, and length of the stability index during the eyes-open condition; surface area of the limit of stability (LOS) on the hemiparetic and intact sides, and the auditory continuous performance test and backward visual span test after rehabilitation. Although no significant difference was observed for the changes in balance ability or cognitive, motor, and ADL functions between the groups, changes in the WDI pressure during the eyes-open condition and in the area ratio of LOS (hemiparetic/intact) showed a tendency to improve in the dual-task group. Conclusion Our findings suggest that dual-task training could be as effective as conventional balance training for improving balance and cognition in subacute post-stroke patients.

Background: The aim of this study is to test if adjuvant hydrotherapy with viscosupplement is beneficial on management of pain, stiffness, function, and mental relaxation in knee osteoarthritis (OA). Methods: Nineteen patients with OA were randomly assigned to hydrotherapy or control groups. All patients received viscosupplement injections once a week for 3 weeks. Hydrotherapy group (n=9) had a spa containing green tea, 3 days a week for 2 weeks. The control group (n=10) received only injections. All patients were assessed at baseline and after the third injection. All were assessed for pain (visual analog scale, VAS), pain severity, and functional status (Western Ontario and McMaster Universities osteoarthritis index, WOMAC), emotional status, quality of life (Euro quality of life health-related quality of life inventory five dimension, EQ-5D), and relative spectral power of alpha waves in electroencephalography (EEG). Results: Both groups reported a statistically significant reduction of pain at the end of treatment and detailed assessment of pain, and function in WOMAC and the relative power of alpha in electroencephalogram showed statistical significant difference only in the hydrotherapy group. However, there were no significant intergroup differences, except for VAS score. Conclusion: Adjuvant 2-week hydrotherapy to viscosupplement might have a modest role in the management of pain and functional disability and the mental relaxation in patients with knee OA. Larger, randomized controlled trials with intervention of long term period to determine efficacy in treating knee OA are warranted.

Hemiballism describes involuntary severe, violent, arrhythmic, rotatory and large amplitude movements of limb from proximal joint. We experienced an elderly stroke patient with hemiballism accompanied dysphagia that persisted for several months severity was evaluated by the Universidade Federal de Minas Gerais Sydenham’s chorea rating scale (USCRS) and video fluoroscopic swallowing study (VFSS). In this case, we observed the improvement of hemiballism by conventional rehabilitation therapy and low dose quetiapine. Therefore, we recommend geriatrists considers vthese therapies in elderly patients with hemiballism.

We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova feedback. For dust, we consider a simplified model of grain size distribution by representing the entire range of grain sizes with large and small grains. We include dust production in stellar ejecta, dust destruction by supernova (SN) shocks, grain growth by accretion and coagulation, and grain disruption by shattering. We find that the assumption of fixed dust-to-metal mass ratio becomes no longer valid when the galaxy is older than 0.2 Gyr, at which point the grain growth by accretion starts to contribute to the nonlinear rise of dust-to-gas ratio. As expected in our previous one-zone model, shattering triggers grain growth by accretion since it increases the total surface area of grains. Coagulation becomes significant when the galaxy age is greater than $\sim$ 1 Gyr: at this epoch the abundance of small grains becomes high enough to raise the coagulation rate of small grains. We further compare the radial profiles of dust-to-gas ratio $(\mathcal{D})$ and dust-to-metal ratio $(\mathcal{D}/Z)$ (i.e., depletion) at various ages with observational data. We find that our simulations broadly reproduce the radial gradients of dust-to-gas ratio and depletion. In the early epoch ($\lesssim 0.3$ Gyr), the radial gradient of $\mathcal{D}$ follows the metallicity gradient with $\mathcal{D}/Z$ determined by the dust condensation efficiency in stellar ejecta, while the $\mathcal{D}$ gradient is steeper than the $Z$ gradient at the later epochs because of grain growth by accretion. The framework developed in this paper is applicable to any SPH-based galaxy evolution simulations including cosmological ones., 18 pages, 16 figures, published on MNRAS

We examine the duty cycle and the history of star formation (SFH) for high-redshift galaxies at z>=6 using cosmological hydrodynamic simulations. We find that, even though individual galaxies have bursty SFH, the averaged SFH between z~15 to z=6 can be characterized well by either an exponentially increasing functional form with characteristic time-scales of 70 Myr to 200 Myr for galaxies with stellar masses Ms~10^6 Msun to >10^10 Msun respectively, or by a simple power-law form which exhibits a similar mass dependent time-scales. Using the SFH of individual galaxies, we measure the duty cycle of star formation (DC_SFH); i.e., the fraction of time a galaxy of a particular mass spends above a star formation rate (SFR) threshold which would make it observable to the Hubble Space Telescope (HST) during a given epoch. We also examine the fraction of galaxies at a given redshift that are brighter than a rest-frame UV magnitude (Muv ~ -18), which is sufficient enough to make them observable (DC_Muv). We find that both DC_SFH and DC_Muv make a sharp transition from zero (for galaxies with Ms 10^9 Msun). The measured duty cycle is also manifested in the intrinsic scatter in the Ms-SFR relationship (~ 1 dex) and Ms-Muv relationship (\Delta Muv ~ +-1 mag). We provide analytic fits to the DC as a function of Ms using a sigmoid function, which can be used to correct for catalogue incompleteness. We consider the effects of duty cycle to the observational estimate of galaxy stellar mass functions (GSMF) and the star formation rate density (SFRD), and find that it results in a much shallower low-mass end slopes of the GSMF and a reduction of >~ 70% of our intrinsic SFRD, making our simulation results more compatible with observational estimates.

We present the results of a numerical study comparing photometric and physical properties of simulated z=6-9 galaxies to the observations taken by the WFC3 instrument aboard the Hubble Space Telescope. Using cosmological hydrodynamical simulations we find good agreement with observations in color-color space at all studied redshifts. We also find good agreement between observations and our Schechter luminosity function fit in the observable range, Muv =6.

There are mainly two different approaches to measure the cosmic star formation history: direct star formation rate density (SFRD) and stellar mass density rhostar as functions of redshift. Compilations of current observations seem to show a disparity in the two quantities, in the sense that the integral of SFRD is higher than the observed rhostar (after considering gas recycling). Using cosmological smoothed particle hydrodynamics simulations based on the concordance Lambda cold dark matter model, we show that the two quantities become more consistent with each other when we consider the observed galaxy mass limit. The comparison between simulations and (dust corrected) observed cosmic SFRD shows a good agreement, while the observed rhostar is significantly lower than the simulation results. This can be reconciled if the current high-$z$ galaxy surveys are missing faint low-mass galaxies due to their flux limit. Our simulated GSMFs have steep low-mass end slopes of alpha 3, and when these numerous low-mass galaxies are included, the total rhostar matches with the integral of SFRD.

Prompted by various analyses of long (Type II) GRB rates and their relationship to the cosmic star-formation history, metallicity and luminosity function evolution, we systematically analyze these effects with a Monte Carlo code. We test various cosmic star-formation history models including analytical and empirical models as well as those derived from cosmological simulations. We also explore expressions for metallicity enhancement of the GRB rate with redshift, as presented in the literature, and discuss improvements to these analytic expressions from the point of view of galactic evolution. These are also compared to cosmological simulations on metal enrichment. Additionally we explore possible evolutionary effects of the GRB rate and luminosity function with redshift. The simulated results are tested with the observed Swift sample including the L, z, and peak flux (log N-log P) distributions. The observational data imply that an increase in the GRB rate is necessary to account for the observations at high redshift, although the form of this enhancement is unclear. A rate increase due to lower metallicity at higher redshift may not be the singular cause and is subject to a variety of uncertainties. Alternatively, evolution of the GRB luminosity function break with redshift shows promise as a possible alternative.

Combing the three-dimensional radiative transfer (RT) calculation and cosmological SPH simulations, we study the escape fraction of ionizing photons (f_esc) of high-redshift galaxies at z=3-6. Our simulations cover the halo mass range of M_h = 10^9 - 10^12 M_sun. We postprocess several hundred simulated galaxies with the Authentic Radiative Transfer (ART) code to study the halo mass dependence of f_esc. In this paper, we restrict ourselves to the transfer of stellar radiation from local stellar population in each dark matter halo. We find that the average f_esc steeply decreases as the halo mass increases, with a large scatter for the lower mass haloes. The low mass haloes with M_h ~ 10^9 M_sun have large values of f_esc (with an average of ~ 0.4), whereas the massive haloes with M_h ~ 10^11 M_sun show small values of f_esc (with an average of ~ 0.07). This is because in our simulations, the massive haloes show more clumpy structure in gas distribution, and star-forming regions are embedded inside these clumps, making it more difficult for the ionizing photons to escape. On the other hand, in low mass haloes, there are often conical regions of highly ionized gas due to the shifted location of young star clusters from the center of dark matter halo, which allows the ionizing photons to escape more easily than in the high-mass haloes. By counting the number of escaped ionizing photons, we show that the star-forming galaxies can ionize the intergalactic medium at z=3-6. The main contributor to the ionizing photons is the haloes with M_h < 10^10 M_sun owing to their high f_esc. The large dispersion in f_esc suggests that there may be various sizes of H{\sc ii} bubbles around the haloes even with the same mass in the early stages of reionization. We also examine the effect of UV background radiation field on f_esc using simple, four different treatment of UV background.

We study the impact of ultraviolet background (UVB) radiation field and the local stellar radiation on the H_I column density distribution f(N_HI) of damped Ly-alpha systems (DLAs) and sub-DLAs at z=3 using cosmological smoothed particle hydrodynamics simulations. We find that, in the previous simulations with an optically thin approximation, the UVB was sinking into the H_I cloud too deeply, and therefore we underestimated the f(N_HI) at 19 < log(N_HI) < 21.2 compared to the observations. If the UVB is shut off in the high-density regions with n_gas > 6 x 10^{-3} cm^{-3}, then we reproduce the observed f(N_HI) at z=3 very well. We also investigate the effect of local stellar radiation by post-processing our simulation with a radiative transfer code, and find that the local stellar radiation does not change the f(N_HI) very much. Our results show that the shape of f(N_HI) is determined primarily by the UVB with a much weaker effect by the local stellar radiation and that the optically thin approximation often used in cosmological simulation is inadequate to properly treat the ionization structure of neutral gas in and out of DLAs. Our result also indicates that the DLA gas is closely related to the transition region from optically-thick neutral gas to optically-thin ionized gas within dark matter halos., 5 pages, 3 figures, uses emulateapj. ApJL in press. Corrected a plotting error in Fig. 3, which reduced the effect of local stellar radiation on f(N_HI)

We develop a new ``Multicomponent and Variable Velocity'' (MVV) galactic outflow model for cosmological smoothed particle hydrodynamic (SPH) simulations. The MVV wind model reflects the fact that the wind material can arise from different phases in the interstellar medium (ISM), and the mass-loading factor in the MVV model is a function of galaxy stellar mass. We find that the simulation with the MVV outflow has the following characteristics: (i) the intergalactic medium (IGM) is hardly heated up, and the mean IGM temperature is almost the same as in the no-wind run; (ii) it has lower cosmic star formation rates (SFRs) compared to the no-wind run, but higher SFRs than the constant velocity wind run; (iii) it roughly agrees with the observed IGM metallicity, and roughly follows the observed evolution of Omega(Civ); (iv) the lower mass galaxies have larger mass-loading factors, and the low-mass end of galaxy stellar mass function is flatter than in the previous simulations. Therefore, the MVV outflow model mildly alleviates the problem of too steep galaxy stellar mass function seen in the previous SPH simulations. In summary, the new MVV outflow model shows reasonable agreement with observations, and gives better results than the constant velocity wind model.

We investigate the effects of the change of cosmological parameters and star formation (SF) models on the cosmic SF history using cosmological smoothed particle hydrodynamics (SPH) simulations based on the cold dark matter (CDM) model. We vary the cosmological parameters within 1-sigma error from the WMAP best-fit parameters, and find that such changes in cosmological parameters mostly affect the amplitude of the cosmic SF history. At high redshift (hereafter high-z), the star formation rate (SFR) is sensitive to the cosmological parameters that control the small-scale power of the primordial power spectrum, while the cosmic matter content becomes important at lower redshifts. We also test two new SF models: 1) the `Pressure' model based on the work by Schaye & Dalla Vecchia (2008), and 2) the `Blitz' model that takes the effect of molecular hydrogen formation into account, based on the work by Blitz & Rosolowsky (2006). Compared to the previous conventional SF model, the Pressure model reduces the SFR in low-density regions and shows better agreement with the observations of the Kennicutt-Schmidt law. This model also suppresses the early star formation and shifts the peak of the cosmic SF history toward lower redshift, more consistently with the recent observational estimates of cosmic SFR density. The simulations with the new SF model also predict lower global stellar mass densities at high-z, larger populations of low-mass galaxies and a higher gas fraction in high-z galaxies. Our results suggest that there is room left in the model uncertainties to reconcile the discrepancy that was found between the theory and observations of cosmic SF history and stellar mass density. Nevertheless, our simulations still predict higher stellar mass densities than most of the observational estimates.

We investigate the physical mechanisms of tidal heating and satellite disruption in cold dark matter host haloes using N-body simulations based on cosmological initial conditions. We show the importance of resonant shocks and resonant torques with the host halo to satellite heating. A resonant shock (torque) couples the radial (tangential) motion of a satellite in its orbit to its phase space. For a satellite on a circular orbit, an ILR-like resonance dominates the heating and this heating results in continuous satellite mass loss. We estimate the requirements for simulations to achieve these dynamics using perturbation theory. Both resonant shocks and resonant torques affect satellites on eccentric orbits. We demonstrate that satellite mass loss is an outside-in process in energy space; a satellite's stars and gas are thus protected by their own halo against tidal stripping. We simulate the evolution of a halo similar to the Large Magellanic Cloud (LMC) in our Galactic dark matter halo and conclude that the LMC stars have not yet been stripped. Finally, we present a simple algorithm for estimating the evolution of satellite mass that includes both shock heating and resonant torques., 19 pages, 24 figures, accepted for publication in to MNRAS. A full resolution version is available at http://www.physics.unlv.edu/~jhchoi/astro-ph/Disruption.pdf

Density inhomogeneity in the intergalactic medium (IGM) can boost the recombination rate of ionized gas substantially, affecting the growth of HII regions during reionization. Previous attempts to quantify this effect typically failed to resolve down to the Jeans scale in the pre-ionization IGM, which is important in establishing this effect, along with the hydrodynamical back-reaction of reionization on it. Towards that end, we perform a set of fully-coupled, radiation-hydrodynamics simulations from cosmological initial conditions, extending the mass resolution of previous work to the scale of minihalos. Pre-reionization structure is evolved until a redshift $z_i$ at which the ionizing radiation from external sources arrives to sweep an R-type ionization front supersonically across the volume in a few Myr, until it is trapped on the surfaces of minihalos and converted to D-type, after which the minihalo gas is removed by photoevaporative winds. Small-scale density structures during this time lead to a high ($>$10) clumping factor for ionized gas, which hugely boosts the recombination rate until the structures are disrupted by the hydrodynamic feedback after $\sim 10-100~\rm{Myr}$. For incoming stellar radiation with intensity $J_{21}$ in a $200~h^{-1}~\rm{kpc}$ box with the mean density contrast $\bar\delta$, the number of extra recombinations per H atom, on top of what is expected from homogeneously distributed gas, is given by $0.32[J_{21}]^{0.12}[(1+z_i)/11]^{-1.7}[1+\bar\delta]^{2.5}$. In models in which most of the volume is ionized toward the end of reionization, this can add more than one recombination per H atom to the ionizing photon budget to achieve reionization., Comment: 21 pages, 19 figure, Accepted to ApJ

Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization, itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. Reionization modelling requires simulating volumes large enough [~(100Mpc)^3] to sample reionization "patchiness", while resolving millions of galaxy sources above ~10^8 Msun , combining gravitational and gas dynamics with radiative transfer. Modelling the Local Group requires initial cosmological density fluctuations pre-selected to form the well-known structures of the local universe today. Cosmic Dawn ("CoDa") is the first such fully-coupled, radiation-hydrodynamics simulation of reionization of the local universe. Our new hybrid CPU-GPU code, RAMSES-CUDATON, performs hundreds of radiative transfer and ionization rate-solver timesteps on the GPUs for each hydro-gravity timestep on the CPUs. CoDa simulated (91Mpc)^3 with 4096^3 particles and cells, to redshift 4.23, on ORNL supercomputer Titan, utilizing 8192 cores and 8192 GPUs. Global reionization ended slightly later than observed. However, a simple temporal rescaling which brings the evolution of ionized fraction into agreement with observations also reconciles ionizing flux density, cosmic star formation history, CMB electron scattering optical depth and galaxy UV luminosity function with their observed values. Photoionization heating suppressed the star formation of haloes below ~2 x 10^9 Msun , decreasing the abun- dance of faint galaxies around MAB_1600 = [-10,-12]. For most of reionization, star formation was dominated by haloes between 10^10 - 10^11 Msun , so low-mass halo suppression was not reflected by a distinct feature in the global star formation history. (Abridged), Comment: 26 pages, 16 figures, accepted in MNRAS

(Abbreviated) We investigate the dynamical mechanisms responsible for producing tidal tails from dwarf satellites using N-body simulations. We identify two important dynamical co-conspirators: 1) the points where the attractive force of the host halo and satellite are balanced do not occur at equal distances from the satellite centre or at the same equipotential value for massive satellites, breaking the morphological symmetry of the leading and trailing tails; and 2) the escaped ejecta in the leading (trailing) tail continues to be decelerated (accelerated) by the satellite's gravity leading to large offsets of the ejecta orbits from the satellite orbit. The effect of the satellite's self gravity decreases only weakly with a decreasing ratio of satellite mass to host halo mass, demonstrating the importance of these effects over a wide range of subhalo masses. Not only will the morphology of the leading and trailing tails for massive satellites be different, but the observed radial velocities of the tails will be displaced from that of the satellite orbit; both the displacement and the peak radial velocity is proportional to satellite mass. If the tails are assumed to follow the progenitor satellite orbits, the tails from satellites with masses greater than 0.0001 of the host halo virial mass in a spherical halo will appear to indicate a flattened halo. Therefore, a constraint on the Milky Way halo shape using tidal streams requires mass-dependent modelling. Similarly, we compute the the distribution of tail orbits both in E_{r}-r^{-2} space and in E-L_{z} space, advocated for identifying satellite stream relics. The acceleration of ejecta by a massive satellite during escape spreads the velocity distribution and obscures the signature of a well-defined ``moving group'' in phase space.

We use cosmological adaptive mesh refinement (AMR) code Enzo zoom-in simulations to study the long term evolution of the collapsing gas within dark matter (DM) halos at high redshifts. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds at high z. To circumvent the Courant condition at small radii, we have used the sink particle method, and focus on the evolution on scales ~0.01-10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc, and with no detected fragmentation. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. Their mass never exceeds ~10^3 Mo, with the sole exception of the central seed which grows dramatically to ~ 2 x 10^6 Mo in ~2 Myr, confirming the feasibility of this path to the SMBH. The time variability of angular momentum axis in the accreted gas results in the formation of two misaligned disks --- a small inner disk, and a more massive, outer disk which is inclined by ~45^o to the inner disk. The self-gravity of these disks is heavily diluted --- both disks lie within the Roche limit of the central seed. While the inner disk is geometrically thin and weakly asymmetric, the outer disk flares due to turbulent motions as a result of the massive inflow along a pair of penetrating filaments. The geometry of inflow via filaments determines the dominant and secondary Fourier modes in this disk --- these modes have a non-self-gravitational origin. We do not confirm that m=1 is a principal mode that drives the inflow in the presence of a central massive object. While the positions of the disks depend on the scale chosen to break the self-similar collapse, the overall configuration appears to be generic, and is expected to form when the central seed becomes sufficiently massive., 14 pages, 11 figures, MNRAS, in press, typos corrected

The purpose of this study was to investigate the effects of the formative assessment-based teaching strategy on the students’ science concept understanding, learning motivation, and meta-cognitive ability. Students’ perceptions towards this teaching strategy were also examined. Four classes were chosen from a middle school in Busan. Formative assessment-based teaching strategy developed for this study was applied to the experimental group of 2 classes and the traditional teaching strategy was applied to the control group of other 2 classes. The tests of students’ learning motivation, meta-cognitive ability were administered before and after the instruction period. The science concept understanding test was administered only after the instruction. The results showed that the new teaching strategy was more effective for enhancing students’ concept understanding and learning motivation than the traditional teaching strategy. However, there was no significant difference in metacognitive ability between two groups. From the survey of students’ perception, it was found that students thought that the new teaching strategy motivated them to learn and was

We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at $z\sim 6-12$, in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent in the "normal" region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on both environments, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR-stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in volume-filling factor of hot, high-metallicity gas which is near unity for CW, while it remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent in the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties to those of host galaxies. Further constraints on the state of the IGM at high-$z$ are needed to separate different wind models., Comment: 22 pages, 15 figures, accepted for publication in the Astrophysical Journal

Purpose To investigate cardiorespiratory responses during exercise stress tests using an aquatic treadmill and a land-based treadmill in patients with coronary artery disease (CAD). Methods Twenty-one stable CAD patients were enrolled. All patients participated in 2 symptom-limited incremental exercise tests, using both an aquatic and a land treadmill. For the aquatic treadmill protocol, patients were submerged to the upper waist in 28°C water. The treadmill speed started at 2.0 km/h and increased 0.5 km/h every minute thereafter. For the land treadmill protocol, the speed and gradient were started at 2.4 km/h and 1.5%, respectively. The speed was increased by 0.3 km/h and grade by 1% every minute thereafter. Oxygen consumption ((Equation is included in full-text article.)O2), heart rate (HR), and respiratory exchange ratio were measured continuously and peak values recorded. Rating of perceived exertion, percentage of age-predicted maximal HR, and total exercise duration were also recorded. Results Peak cardiorespiratory responses during both protocols were compared. The peak (Equation is included in full-text article.)O2 and peak HR did not show any significant differences. The peak respiratory exchange ratio was significantly greater using the land treadmill than the aquatic treadmill protocol. Rating of perceived exertion, age-predicted maximal HR percentage, and total exercise duration were similar for both protocols. There was a significant linear relationship between HR and (Equation is included in full-text article.)O2 with both protocols. Conclusions This study demonstrated that aquatic treadmill exercise elicits similar peak cardiorespiratory responses compared with land treadmill exercise, suggesting that aquatic treadmill exercise may be effective for CAD patients in cardiac rehabilitation.

We have explored prevailing modes of galaxy growth for redshifts z ~ 6-14, comparing substantially overdense and normal regions of the universe, using high-resolution zoom-in cosmological simulations. Such rare overdense regions have been projected to host high-z quasars. We demonstrate that galaxies in such environments grow predominantly by a smooth accretion from cosmological filaments which dominates the mass input from major, intermediate and minor mergers. We find that by z ~6, the accumulated galaxy mass fraction from mergers falls short by a factor of 10 of the cumulative accretion mass for galaxies in the overdense regions, and by a factor of 5 in the normal environments. Moreover, the rate of the stellar mass input from mergers also lies below that of an in-situ star formation (SF) rate. The fraction of stellar masses in galaxies contributed by mergers in overdense regions is ~12%, and ~33% in the normal regions, at these redshifts. Our median SF rates for ~few X 10^9 Mo galaxies agrees well with the recently estimated rates for z ~ 7 galaxies from Spitzer's SURF-UP survey. Finally, we find that the main difference between the normal and overdense regions lies in the amplified growth of massive galaxies in massive dark matter halos. This leads to the formation of >= 10^{10} Mo galaxies due to the ~100-fold increase in mass during the above time period. Such galaxies are basically absent in the normal regions at these redshifts., 6 pages, 4 figures, Astrophysical Journal Letters, in press

Recent observations have indicated the existence of dust in high-redshift galaxies, however, the dust properties in them are still unknown. Here we present theoretical constraints on dust properties in Lyman break galaxies (LBGs) at z=3 by post-processing a cosmological smoothed particle hydrodynamics simulation with radiative transfer calculations. We calculate the dust extinction in 2800 dark matter halos using the metallicity information of individual gas particles in our simulation. We use only bright galaxies with rest-frame UV magnitude M_1700 < -20 mag, and study the dust size, dust-to-metal mass ratio, and dust composition. From the comparison of calculated color excess between B and V-band (i.e., E(B-V)) and the observations, we constrain the typical dust size, and show that the best-fitting dust grain size is ~ 0.05 micron, which is consistent with the results of theoretical dust models for Type-II supernova. Our simulation with the dust extinction effect can naturally reproduce the observed rest-frame UV luminosity function of LBGs at z=3 without assuming an ad hoc constant extinction value. In addition, in order to reproduce the observed mean E(B-V), we find that the dust-to-metal mass ratio needs to be similar to that of the local galaxies, and that the graphite dust is dominant or at least occupy half of dust mass., 13 pages, 13 figures, accepted for publication in MNRAS

Using an isolated Milky Way-mass galaxy simulation, we compare results from 9 state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly-formed stellar clump mass functions show more significant variation (difference by up to a factor of ~3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low density region, and between more diffusive and less diffusive schemes in the high density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes., 28 pages, 35 figures, Accepted for publication in the Astrophysical Journal, Image resolution greatly reduced, High-resolution version of this article is available at http://www.jihoonkim.org/agora/AGORA_Paper4_draft.pdf, The first paper of the AGORA Initiative is at http://adsabs.harvard.edu/abs/2014ApJS..210...14K, More information on AGORA is at http://www.AGORAsimulations.org/