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Spontaneous remission of B-lymphoblastic leukemia (B-ALL) in the setting of viral and bacterial infections has been reported. Here, we present a case of B-ALL that showed a complete remission in the setting of group A streptococcal bacteremia. The patient was an 11-year-old boy who presented with a sore throat, right ear pain, and rhinorrhea. Prior to the diagnosis of B-ALL, he was diagnosed with streptococcal pharyngitis and received a single dose of dexamethasone and azithromycin. One day later, he was found to be pancytopenic and an immunophenotypically abnormal B-lymphoblastic population was detected comprising 0.6% and 16.8% of the peripheral blood and bone marrow cells, respectively. Though a diagnosis of B-ALL was highly suspected, blast percentage was <20% and the bone marrow showed relatively unremarkable trilineage hematopoiesis. On close monitoring, the suspected neoplastic population became undetectable by day 17 and the patient’s complete blood count (CBC) completely normalized by day 46. On day 82, a peripheral blood smear demonstrated circulating blasts. Flow cytometry of a bone marrow aspirate revealed B-lymphoblastic leukemia accounting for 94% nucleated cells, consistent with the diagnosis of B-lymphoblastic leukemia. This case is of interest as less than 20 examples of spontaneous remission of B-ALL have been reported in the literature. As the case reported here relapsed and previously reported spontaneously remitting cases have uniformly relapsed, cases of B-ALL with spontaneous remission should be followed very closely for recurrence.

Anesthesiology and anesthesiologists have a tremendous opportunity and responsibility to eliminate health disparities and to achieve health equity. We thus examine health disparity and health equity through the lens of anesthesiology and the perspective of anesthesiologists. In this paper, we define health disparity and health care disparities and provide tangible, representative examples of the latter in the practice of anesthesiology. We define health equity, primarily as the desired antithesis of health disparity. Finally, we propose a framework for anesthesiologists, working toward mitigating health disparity and health care disparities, advancing health equity, and documenting improvements in health care access and health outcomes. This multilevel and interdependent framework includes the perspectives of the patient, clinician, group or department, health care system, and professional societies, including medical journals. We specifically focus on the interrelated roles of social identity and social determinants of health in health outcomes. We explore the foundational role that clinical informatics and valid data collection on race and ethnicity have in achieving health equity. Our ability to ensure patient safety by considering these additional patient-specific factors that affect clinical outcomes throughout the perioperative period could substantially reduce health disparities. Finally, we explore the role of medical journals and their editorial boards in ameliorating health disparities and advancing health equity.

Cooperation motives are traditionally elicited in experimental games where players have misaligned interests that yield noncooperation in equilibrium. Research finds a typology of behavioral types such as free riders and conditional cooperators. However, intrinsic motives in conflict settings such as appeasement, punishment, and greed are elusive in such games where noncooperation is the equilibrium prediction. To identify types in the dark side of human interaction, we apply hierarchical cluster analysis to data from the Vendetta Game, which has a payoff structure similar to public goods games but a dynamic move structure that yields cooperation in equilibrium. It allows us to observe diverse non-equilibrium conflict strategies, and to understand how feuds perpetuate. We relate our method and typology to other social dilemmas.

We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining the scenario of a cloud–cloud collision. We utilize the CARMA–NRO Orion survey 13CO (1–0) data to compare molecular gas to the properties of young stellar objects from the SDSS III IN-SYNC survey. We show that the increase of $v_{\rm {}^{13}CO} - v_{\rm YSO}$and Σ scatter of older YSOs can be signals of cloud–cloud collision. SOFIA-upGREAT 158 μm [C ii] archival data toward the northern part of Orion A are also compared to the 13CO data to test whether the position and velocity offsets between the emission from these two transitions resemble those predicted by a cloud–cloud collision model. We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3, and OMC-4, shows qualitative agreements with the cloud–cloud collision scenario, while in one of the southern regions, NGC 1999, there is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster, L 1641 N, shows slight tendencies of cloud–cloud collision. Overall, our results support the cloud–cloud collision process as being an important mechanism for star cluster formation in Orion A.

The severe acute respiratory syndrome coronavirus 2 (coronavirus disease 2019 [COVID-19]) pandemic has challenged medical systems and clinicians globally to unforeseen levels. Rapid spread of COVID-19 has forced clinicians to care for patients with a highly contagious disease without evidence-based guidelines. Using a virtual modified nominal group technique, the Pediatric Difficult Intubation Collaborative (PeDI-C), which currently includes 35 hospitals from 6 countries, generated consensus guidelines on airway management in pediatric anesthesia based on expert opinion and early data about the disease. PeDI-C identified overarching goals during care, including minimizing aerosolized respiratory secretions, minimizing the number of clinicians in contact with a patient, and recognizing that undiagnosed asymptomatic patients may shed the virus and infect health care workers. Recommendations include administering anxiolytic medications, intravenous anesthetic inductions, tracheal intubation using video laryngoscopes and cuffed tracheal tubes, use of in-line suction catheters, and modifying workflow to recover patients from anesthesia in the operating room. Importantly, PeDI-C recommends that anesthesiologists consider using appropriate personal protective equipment when performing aerosol-generating medical procedures in asymptomatic children, in addition to known or suspected children with COVID-19. Airway procedures should be done in negative pressure rooms when available. Adequate time should be allowed for operating room cleaning and air filtration between surgical cases. Research using rigorous study designs is urgently needed to inform safe practices during the COVID-19 pandemic. Until further information is available, PeDI-C advises that clinicians consider these guidelines to enhance the safety of health care workers during airway management when performing aerosol-generating medical procedures. These guidelines have been endorsed by the Society for Pediatric Anesthesia and the Canadian Pediatric Anesthesia Society.

Pope Francis’s consistent advocacy for the human dignity and rights of migrants in his official pronouncements and actions reveals a pope who not only cares deeply about the existential challenges that migrants face but also articulates solutions to address these challenges. He unequivocally expresses a preferential option for, and commitment to, accompanying migrants in empathy and solidarity. He addresses issues of poverty, economic marginalization, environmental degradation, and racial, political, and religious tensions that drive migration today. For him, migration is a missional issue that undergirds the church’s mission to bring the Good News to everyone, migrants included.

All missions to Mars which have attempted to detect organic molecules have detected simple chlorohydrocarbons, the source of which has yet to be firmly established. This study assessed the likelihood of these chlorinated molecules being indigenous to the sedimentary units in which they were detected or if they were chlorinated during analysis. The survivability of 1‐chloronapthalene was examined via hydrous pyrolysis experiments and its dechlorination kinetics were determined. The results of these experiments were used to model the survivability of this simple chlorohydrocarbon under Mars‐relevant diagenetic conditions using the Sheepbed mudstone unit as a case study. It was found that 1‐chloronapthalene was rapidly dechlorinated under Noachian conditions, and thus, the detected Martian chlorohydrocarbons are unlikely to be ancient and probably formed within the rover's sample handling chain during analysis. The search for past or present life on Mars is centered on the detection of organic molecules. Most attempts to detect organic molecules on Mars have only found simple chlorinated compounds. The source of these chlorinated compounds has not been firmly established. It has been hypothesized that chlorinated organic compounds could form on the Martian surface via reactions between chlorine‐bearing salts and organic compounds delivered by meteorites. This study examined the ability of simple chlorinated organic molecules to survive the high pressures and temperatures associated with burial over geological time scales. Our aim was to calculate whether chlorinated molecules detected on Mars could be ancient and preserved in the rock units, or if they formed during the analysis process, as other studies have assumed. It was found that, on a warmer ancient Mars when the sediments the chlorinated molecules were detected in were deposited, the increased surface temperatures would have promoted the loss of chlorine relatively rapidly, and the intact chlorinated organic molecules would not have survived the burial and exhumation processes to the present day. The chlorinated organics detected on Mars are therefore likely to have been formed recently, most probably through reactions with chlorine‐bearing salts when heated during analysis. The survivability of 1‐chloronapthalene during diagenesis has been modeled for Mars‐relevant conditionsChlorohydrocarbons are unlikely to survive until present under Noachian diagenetic conditionsChlorohydrocarbons detected by MSL appear likely to have been chlorinated during analysis

•We experimentally analyze behavior in repeated games when helping people in one's group hurts those in other groups.•Intergroup conflict aversion weakens intragroup cooperation as cooperation decreases with the degree of rivalry with the outgroup.•Cooperation increases with the degree of synergy with partners and previous cooperation by partners but not rivals.•To understand the motives and strategies that drive such behavior, we use a structural model to estimate group-specific social preferences and cooperative strategies.•It shows that boundedly rational participants cooperate with partners if they expect profits from mutual cooperation, but stop once partners defect, and avoid conflict because they are altruistic to rivals.

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Hematopoietic stem/progenitor cells (HSPC) differentiate in the context of stromal niches producing cells of multiple lineages. Limited success has been achieved in the past with induction of hematopoiesis in vitro. Previously, spleen long-term stromal cultures (LTC) were shown to continuously support restricted hematopoiesis for production of novel dendritic-like cells (LTC-DC). An in vivo equivalent dendritic cell type was then described which is specific for spleen. The in vivo counterpart cell was termed ‘L-DC’ and represents a dendritic-like CD11cloCD11bhiCD8α-MHC-II- cell which differs phenotypically and functionally from monocytes/macrophages and conventional and plasmacytoid DC. Splenic stroma is now shown to maintain HSPC and to support their restricted in vitro differentiation to give this ‘L-DC’ subset. In order to characterise progenitors of this distinct cell type, LTC were analysed for cell subsets produced, and these subsets sorted and assessed for hematopoietic potential in subsequent co-cultures over STX3 stroma. Progenitors were defined as a lineage (Lin)-ckitlo subset reflecting HSPC. Furthermore, when Lin-ckithiSca1+Flt3- HSPC were sorted from bone marrow, they colonised splenic stroma with long-term production of L-DC. The maintenance of HSPC by splenic stroma was confirmed when non-adherent cells collected from LTC showed oligopotent reconstitution of the hematopoietic compartment of lethally irradiated mice. All data support a model whereby spleen houses a niche for HSPC in the resting state, with production of progenitors, and their differentiation to give tissue-specific antigen presenting cells.

In this study, we sought to determine whether neuraxial anesthesia to facilitate external cephalic version (ECV) increased delivery costs for breech fetal presentation.

The spleen contains a novel antigen presenting a cell type which develops from endogenous hematopoietic progenitors. The main DC subsets in murine spleen arise from BM‐derived precursors. Recently, a novel APC type was described in spleen. To determine if spleen contains the progenitors of this subset, a stromal coculture system was used to assess candidate progenitors for their hematopoietic potential. Here, the progenitor of that subset is identified as a spleen endogenous Lin−c‐kitlohematopoietic progenitor and is most highly enriched among the Lin−c‐kitloCD34+subset. Dendritic‐like cells produced in vitro functionally resemble the previously described in vivo equivalent subset with high endocytic capacity and capability for antigen‐specific activation of CD8+T cells but not CD4+T cells.

Dendritic cells (DC) are important antigen presenting cells (APC) which induce and control the adaptive immune response. In spleen alone, multiple DC subsets can be distinguished by cell surface marker phenotype. Most of these have been shown to develop from progenitors in bone marrow and to seed lymphoid and tissue sites during development. This study advances in vitro methodology for haematopoiesis of dendritic-like cells from progenitors in spleen. Since spleen progenitors undergo differentiation in vitro to produce these cells, the possibility exists that spleen represents a specific niche for differentiation of this subset. The fact that an equivalent cell subset has been shown to exist in spleen also supports that hypothesis. Studies have been directed at investigating the specific functional role of this novel subset as an APC accessible to blood-borne antigen, as well as the conditions under which haematopoiesis is initiated in spleen, and the type of progenitor involved.

Hematopoietic cell lineages are best described in terms of distinct progenitors with limited differentiative capacity. To distinguish cell lineages, it is necessary to define progenitors and induce their differentiation in vitro. We previously reported in vitro development of immature dendritic-like cells (DCs) in long-term cultures (LTCs) of murine spleen, and in cocultures of spleen or bone marrow (BM) over splenic endothelial cell lines derived from LTCs. Cells produced are phenotypically distinct CD11bhiCD11cloCD8−MHC-II− cells, tentatively named L-DCs. Here we delineate L-DC progenitors as different from known DC progenitors in BM and DC precursors in spleen. The progenitor is contained within the lineage-negative (Lin)−c-kit+ subset in neonatal and adult spleen. This subset has multipotential reconstituting ability in mice. In neonatal spleen, the progenitor is further enriched within the c-kitlo and CD34+ subsets of Lin−c-kit+ cells. These cells seed cocultures of splenic endothelial cells, differentiating to give L-DCs that can activate T cells. L-DC progenitors are distinguishable from described splenic CD11clo DC precursors and from Fms-like tyrosine kinase 3+ DC progenitors in BM. Overall, this study confirms that LTCs are a physiologically relevant culture system for in vitro development of a novel DC type from spleen progenitors.

Hematopoietic cell lineages are best described in terms of distinct progenitors with limited differentiative capacity. To distinguish cell lineages, it is necessary to define progenitors and induce their differentiation in vitro. We previously reported in vitro development of immature dendritic-like cells (DCs) in long-term cultures (LTCs) of murine spleen, and in cocultures of spleen or bone marrow (BM) over splenic endothelial cell lines derived from LTCs. Cells produced are phenotypically distinct CD11bhiCD11cloCD8−MHC-II−cells, tentatively named L-DCs. Here we delineate L-DC progenitors as different from known DC progenitors in BM and DC precursors in spleen. The progenitor is contained within the lineage-negative (Lin)−c-kit+subset in neonatal and adult spleen. This subset has multipotential reconstituting ability in mice. In neonatal spleen, the progenitor is further enriched within the c-kitloand CD34+subsets of Lin−c-kit+cells. These cells seed cocultures of splenic endothelial cells, differentiating to give L-DCs that can activate T cells. L-DC progenitors are distinguishable from described splenic CD11cloDC precursors and from Fms-like tyrosine kinase 3+DC progenitors in BM. Overall, this study confirms that LTCs are a physiologically relevant culture system for in vitro development of a novel DC type from spleen progenitors.

Spleen as a lymphoid tissue is specialized for monitoring blood and mounting immunity against blood-borne antigens. Antigen-presenting cells present in spleen commonly develop from bone marrow-derived precursors that enter blood circulation. However, a distinct splenic myeloid antigen-presenting cell subset described in this laboratory, namely “dendritic-like cells” (L-DC), has been hypothesized not to share a bone marrow origin.

We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with a flat rotation curve. We perform a series of three-dimensional adaptive mesh refinement numerical simulations that follow both the global evolution on scales of [?]20 kpc and resolve down to scales [?]10 pc with a multiphase atomic interstellar medium. In this first study, we omit star formation and feedback, and focus on the processes of gravitational instability and cloud collisions and interactions. We define clouds as regions with n H [?] 100 cm-3 and track the evolution of individual clouds as they orbit through the galaxy from their birth to their eventual destruction via merger or via destructive collision with another cloud. After [?]140 Myr a large fraction of the gas in the disk has fragmented into clouds with masses [?]106 M and a mass spectrum similar to that of Galactic GMCs. The disk settles into a quasi-steady-state in which gravitational scattering of clouds keeps the disk near the threshold of global gravitational instability. The cloud collision time is found to be a small fraction, [?]1/5, of the orbital time, and this is an efficient mechanism to inject turbulence into the clouds. This helps to keep clouds only moderately gravitationally bound, with virial parameters of order unity. Many other observed GMC properties, such as mass surface density, angular momentum, velocity dispersion, and vertical distribution, can be accounted for in this simple model with no stellar feedback.

Infrared dark clouds (IRDCs) are cold, dense regions of giant molecular clouds that are opaque at wavelengths [?]10 mm or more and thus appear dark against the diffuse Galactic background emission. They are thought to be the progenitors of massive stars and star clusters. We use 8 mm imaging data from Spitzer Galactic Legacy Mid-Plane Survey Extraordinaire to make extinction maps of 10 IRDCs, selected to be relatively nearby and massive. The extinction mapping technique requires construction of a model of the Galactic IR background intensity behind the cloud, which is achieved by correcting for foreground emission and then interpolating from the surrounding regions. The correction for foreground emission can be quite large, up to [?]50% for clouds at [?]5 kpc distance, thus restricting the utility of this technique to relatively nearby clouds. We investigate three methods for the interpolation, finding systematic differences at about the 10% level, which, for fiducial dust models, corresponds to a mass surface density S = 0.013 g cm-2, above which we conclude that this extinction mapping technique attains validity. We examine the probability distribution function of S in IRDCs. From a qualitative comparison with numerical simulations of astrophysical turbulence, many clouds appear to have relatively narrow distributions suggesting relatively low (less than five) Mach numbers and/or dynamically strong magnetic fields. Given cloud kinematic distances, we derive cloud masses. Rathborne, Jackson, and Simon identified cores within the clouds and measured their masses via millimeter dust emission. For 43 cores, we compare these mass estimates with those derived from our extinction mapping, finding good agreement: typically factors of [?]2 difference for individual cores and an average systematic offset of [?]10% for the adopted fiducial assumptions of each method. We find tentative evidence for a systematic variation of these mass ratios as a function of core density, which is consistent with models of ice mantle formation on dust grains and subsequent grain growth by coagulation, and/or with a temperature decrease in the densest cores.

We conducted a cross-sectional study of Malay participants aged 40–80 years (n = 2,932) to examine the associations between polymorphisms at newly identified, lipid-associated loci with blood lipid levels and prevalent cardiovascular disease (CVD) in a Malay population in Asia. A polymorphism adjacent to the TRIB1 locus (rs17321515) was associated with elevated total cholesterol and LDL-cholesterol (LDL-C) after adjustment for age and sex (both P values <0.007) and with increased risk of coronary heart disease and CVD [odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.03–1.46; and OR 1.2, 95% CI 1.02–1.42, respectively] under an additive model of inheritance. In addition, using recessive models of inheritance, polymorphisms on chromosome 19 adjacent to the CILP2 and PBX4 loci (rs16996148) and on chromosome 1 at the GALNT2 locus (rs4846914) were associated with elevated HDL-C (P = 0.005) and lower LDL-C (P = 0.048), respectively. Although novel, the former is consistent with the association between this polymorphism and lower blood triglycerides observed in the initial studies conducted in populations of European ancestry. Neither showed statistically significant association with CVD. These observations should form the basis of further investigation to identify the causative polymorphisms at this locus, and also to understand the mechanistic roles that this protein may play in lipoprotein metabolism in Asians and other populations.

We conducted a cross-sectional study of Malay participants aged 40–80 years (n = 2,932) to examine the associations between polymorphisms at newly identified, lipid-associated loci with blood lipid levels and prevalent cardiovascular disease (CVD) in a Malay population in Asia. A polymorphism adjacent to the TRIB1 locus (rs17321515) was associated with elevated total cholesterol and LDL-cholesterol (LDL-C) after adjustment for age and sex (both Pvalues <0.007) and with increased risk of coronary heart disease and CVD [odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.03–1.46; and OR 1.2, 95% CI 1.02–1.42, respectively] under an additive model of inheritance. In addition, using recessive models of inheritance, polymorphisms on chromosome 19 adjacent to the CILP2 and PBX4 loci (rs16996148) and on chromosome 1 at the GALNT2 locus (rs4846914) were associated with elevated HDL-C (P= 0.005) and lower LDL-C (P= 0.048), respectively. Although novel, the former is consistent with the association between this polymorphism and lower blood triglycerides observed in the initial studies conducted in populations of European ancestry. Neither showed statistically significant association with CVD. These observations should form the basis of further investigation to identify the causative polymorphisms at this locus, and also to understand the mechanistic roles that this protein may play in lipoprotein metabolism in Asians and other populations.

We investigate the effects of weakly interacting massive particle (WIMP) dark matter annihilation on the formation of Population III.1 (Pop III.1) stars. We consider the relative importance of cooling due to baryonic radiative processes and heating due to WIMP annihilation. We analyze the dark matter and gas profiles of several halos formed in cosmological-scale numerical simulations. The heating rate depends sensitively on the dark matter density profile, which we approximate with a power law $\rho _{\chi }\propto r^{-\alpha _\chi }$, in the numerically unresolved inner regions of the halo. If we assume a self-similar structure so that akh [?] 1.5 as measured on the resolved scales [?]1 pc, then for a fiducial WIMP mass of 100 GeV, the heating rate is typically much smaller (<10-3) than the cooling rate for densities up to n H = 1017 cm-3. In one case, where akh = 1.65, the heating rate becomes similar to the cooling rate by a density of n H = 1015 cm-3. The dark matter density profile is expected to steepen in the central baryon-dominated region [?]1 pc due to adiabatic contraction, and we observe this effect, though with low resolution, in our numerical models. From these we estimate akh [?] 2.0. Heating now dominates cooling above n H [?] 1014 cm-3, in agreement with the study of Spolyar, Freese, & Gondolo. We expect that this leads to the formation of an equilibrium structure with baryonic and dark matter density distributions exhibiting a flattened central core. Examining such equilibria, we find that the total luminosities due to WIMP annihilation are relatively constant and [?]103 L , set by the radiative luminosity of the baryonic core. We discuss the implications for Pop III.1 star formation, particularly the subsequent growth of the protostar. Even if the initial protostar fails to accumulate any additional dark matter, its contraction to the main sequence could be significantly delayed by WIMP annihilation heating, potentially raising the mass scale of Pop III.1 stars to masses [?]100 M .

We have surveyed molecular line emission from Orion BN/KL from 42.3 to 43.6 GHz with the Green Bank Telescope. Sixty-seven lines were identified and ascribed to 13 different molecular species. The spectrum at 7 mm is dominated by SiO, SO2, CH3OCH3, and C2H5CN. Five transitions have been detected from the SiO isotopologues 28SiO, 29SiO, and 30SiO. We report here for the first time the spectra of the 29SiO and 30SiO v = 0 J = 1-0 emission in Orion BN/KL, and show that they have double-peaked profiles with velocity extents similar to the main isotopologue. The main motivation for the survey was the search of high-velocity (100-1000 km s-1) outflows in the BN/KL region as traced by SiO Doppler components. Some of the unidentified lines in principle could be high-velocity SiO features, but without imaging data their location cannot be established. Wings of emission are present in the v = 0 28SiO, 29SiO, and 30SiO profiles, and we suggest that the v = 0 emission from the three isotopologues might trace a moderately high-velocity ([?]30-50 km s-1) component of the flows around the high-mass protostar Source I in the Orion BN/KL region. We also confirm the 7 mm detection of a complex oxygen-bearing species, acetone (CH3COCH3), which has been recently observed toward the hot core at 3 mm, and have found further indications of the presence of long cyanopolyynes (HC5N and HC7N) in the quiescent cold gas of the extended ridge.

We experimentally test the efficacy of indenture as a self‐enforced contract device. In an indenture game, the principal signals the intention of payment on delivery by tearing a banknote in half and giving the agent one half of it as “prepayment”; the agent receives the completing half after delivering the service. By forward induction, cooperation is incentive‐compatibly self‐enforcing. The indenture performs very well, inducing a significantly higher level of cooperation than that in a three‐stage centipede game, which we use to benchmark the natural rate of cooperation. The difference between cooperation rates in both games increases over time.

Supermassive black holes in giant elliptical galaxies are remarkably faint given their expected accretion rates. This motivates models of radiatively inefficient accretion due to either ion-electron thermal decoupling, generation of outflows that inhibit accretion, or settling of gas to a gravitationally unstable disk that forms stars in preference to feeding the black hole. The latter model predicts the presence of cold molecular gas in a thin disk around the black hole. Here we report Submillimeter Array observations of the nucleus of the giant elliptical galaxy M87 that probe 230 GHz continuum and CO ( J = 2-1) line emission. Continuum emission is detected from the nucleus and several knots in the jet, including one that has been undergoing flaring behavior. We estimate a conservative upper limit on the mass of molecular gas within ~100 pc and +-400 km s[?]1 line-of-sight velocity of the central black hole of ~ 8 x 106 M, which includes an allowance for possible systematic errors associated with subtraction of the continuum. Ignoring such errors, we have a 3 s sensitivity to ~ 3 x 106 M. In fact, the continuum-subtracted spectrum shows weak emission features extending up to 4 s above the rms dispersion of the line-free channels. These may be artifacts of the continuum subtraction process. Alternatively, if they are interpreted as CO emission, then the implied molecular gas mass is ~ 5 x 106 M spread out over a velocity range of 700 km s[?]1. These constraints on molecular gas mass are close to the predictions of the model of self-gravitating, star-forming accretion disks fed by Bondi accretion (Tan & Blackman 2005).

We consider the radiative feedback processes that operate during the formation of the first stars. (1) Photodissociation of H2 in the local dark matter minihalo occurs early in the growth of the protostar but does not affect subsequent accretion. (2) Lya radiation pressure acting at the boundary of the H II region that the protostar creates in the accreting envelope reverses infall in the polar directions when the star reaches ~20-30 M but cannot prevent infall from other directions. (3) Expansion of the H II region beyond the gravitational escape radius for ionized gas occurs at masses ~50-100 M. However, accretion from the equatorial regions can continue since the neutral accretion disk shields a substantial fraction of the accretion envelope from direct ionizing flux. (4) At higher stellar masses, ~140 M in the fiducial case, photoevaporation-driven mass loss from the disk, together with declining accretion rates, halts the increase in the protostellar mass. We identify this process as the mechanism that determines the mass of Population III.1 stars (i.e., stars with primordial composition that have not been affected by prior star formation). The initial mass function of these stars is set by the distribution of entropy and angular momentum. The Appendix gives approximate solutions to a number of problems relevant to the formation of the first stars: the effect of Rayleigh scattering on line profiles in media of very large optical depth, the intensity of Lya radiation in very opaque media, radiative acceleration in terms of the gradient of a modified radiation pressure, the flux of radiation in a shell with an arbitrary distribution of opacity, and the vertical structure of an accretion disk supported by gas pressure with constant opacity.

Development of the immune system is depicted as a hierarchical process of differentiation from hematopoietic stem cells (HSC) to lineage-committed precursors, which further develop into mature immune cells. In the case of dendritic cell (DC) development, this linear precursor-progeny approach has led to a confused picture of relationships between various subsets of DC identifiable in vivo. A possible reconciliation of the diversity of DC precursors and DC subsets in vivo encompasses the role of the microenvironment in DC hematopoiesis. We propose here that various niches for DC hematopoiesis within lymphoid organs could account for the diversity of DC in vivo. A tridimensional space consisting of stromal cells which produce a range of membrane-bound and secreted molecules providing signals to DC progenitors would define these niches