Fast molecular outflow from a dusty star-forming galaxy in the early Universe.

Galaxies grow inefficiently, with only a small percentage of the available gas converted into stars each free-fall time. Feedback processes, such as outflowing winds driven by radiation pressure, supernovae, or supermassive black hole accretion, can act to halt star formation if they heat or expel the gas supply. We report a molecular outflow launched from a dust-rich star-forming galaxy at redshift 5.3, 1 billion years after the Big Bang. The outflow reaches velocities up to 800 kilometers per second relative to the galaxy, is resolved into multiple clumps, and carries mass at a rate within a factor of 2 of the star formation rate. Our results show that molecular outflows can remove a large fraction of the gas available for star formation from galaxies at high redshift.

Author Correction: A massive core for a cluster of galaxies at a redshift of 4.3.

Change history: In this Letter, the Acknowledgements section should have included the following sentence: "The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.". This omission has been corrected online.

A massive core for a cluster of galaxies at a redshift of 4.3.

Massive galaxy clusters have been found that date to times as early as three billion years after the Big Bang, containing stars that formed at even earlier epochs1-3. The high-redshift progenitors of these galaxy clusters-termed 'protoclusters'-can be identified in cosmological simulations that have the highest overdensities (greater-than-average densities) of dark matter4-6. Protoclusters are expected to contain extremely massive galaxies that can be observed as luminous starbursts 7 . However, recent detections of possible protoclusters hosting such starbursts8-11 do not support the kind of rapid cluster-core formation expected from simulations 12 : the structures observed contain only a handful of starbursting galaxies spread throughout a broad region, with poor evidence for eventual collapse into a protocluster. Here we report observations of carbon monoxide and ionized carbon emission from the source SPT2349-56. We find that this source consists of at least 14 gas-rich galaxies, all lying at redshifts of 4.31. We demonstrate that each of these galaxies is forming stars between 50 and 1,000 times more quickly than our own Milky Way, and that all are located within a projected region that is only around 130 kiloparsecs in diameter. This galaxy surface density is more than ten times the average blank-field value (integrated over all redshifts), and more than 1,000 times the average field volume density. The velocity dispersion (approximately 410 kilometres per second) of these galaxies and the enormous gas and star-formation densities suggest that this system represents the core of a cluster of galaxies that was already at an advanced stage of formation when the Universe was only 1.4 billion years old. A comparison with other known protoclusters at high redshifts shows that SPT2349-56 could be building one of the most massive structures in the Universe today.

Galaxy growth in a massive halo in the first billion years of cosmic history.

According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly-the first few hundred million years of the Universe-is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.

Early recovery after hip arthroscopy for femoroacetabular impingement syndrome: a prospective, observational study.

The early post-operative course after hip arthroscopy for femoroacetabular impingement syndrome has not been thoroughly characterized or correlated to factors that may influence recovery. The aim of this study was to report on early pain, function and attitudes towards rehabilitation and to determine predictors of early recovery after hip arthroscopy. Sixty-two patients reported pre-operative pain, iHOT-12 (hip functional score), psychological status and other baseline characteristics. Pain, iHOT-12, hip flexion and several other outcomes were measured through 6 weeks post-operative. Baseline characteristics were correlated with outcomes using univariate and multivariable models. Pain relief started on post-operative day 1 and consistently improved throughout the 6 weeks of follow-up. The average patient's pain was reduced from a pre-operative level of 5/10 to 2/10 by 6 weeks post-operative. Similarly, iHOT-12 improved from 33/100 to 57/100 whereas hip flexion increased by 9° by 6 weeks post-operative. At 2 weeks post-operative, pre-operative anti-inflammatory usage was associated with greater improvement in pain and swelling; pre-operative opioid usage with poorer patient-reported helpfulness of and adherence to rehabilitation; and higher ASA (American Society of Anesthesiologists) score and lower procedure time with improvement of the pre-operative pain complaint. At 6 weeks, greater depression was associated with lower post-operative pain reduction but greater pre-operative pain complaint improvement. Continuous passive motion usage was associated with increased hip flexion. Pain improved from pre-operative by Day 1 after hip arthroscopy, and early functional improvements were seen by 6 weeks post-operative. Pre-operative anti-inflammatory and opioid usage, depression, race, ASA score, procedure time and continuous passive motion usage were significantly associated with study outcomes.

Strength and power predictors of sprinting performance in professional rugby players.

AIM: The ability to accelerate and attain high levels of speed is an essential component of success in team sports; however, the physical qualities that underpin these activities remain unclear. This study aimed to determine some of the key strength and power predictors of speed within professional rugby union players. METHODS: Twenty professional male rugby union players participated in this study. Subjects were tested for speed (0-10 m sprint and a flying 10 m sprint), strength (3 repetition maximum squat), lower body power (countermovement jumps [CMJ] and drop jumps [DJ]), reactive strength and leg spring stiffness. The strength and power variables were expressed as absolute values and relative values for analysis. RESULTS: Both relative strength (r=-0.55, P<0.05) and relative power (-0.82, P<0.01) were negatively correlated with 10 m time. Leg spring stiffness and DJ contact time were also related to the flying 10 m time (r=-0.46 and 0.47, respectively, P<0.05) while reactive strength index was negatively related to both the 10 m and flying 10 m times (r=-0.60 and r=-0.62, P<0.05). CONCLUSION: This study provides an insight into those physical attributes that underpin sprinting performance in professional rugby union players and specifically highlights the importance of relative strength and power in the expression and development of different speed components (e.g. acceleration, maximum velocity).

Relationships between salivary free testosterone and the expression of force and power in elite athletes.

AIM: This study examined the predictive relationships between the salivary free testosterone (T) concentrations of elite athletes and the expression of force and power. METHODS: A group of elite male rugby players (N.=64) were assessed for peak force (PF), peak rate of force development (PRFD), force at 100 milliseconds (F100 ms) and 250 milliseconds (F250 ms) during an isometric mid-thigh pull (IMTP), and/or peak power (PP) and height during a countermovement jump (CMJ). Saliva samples were collected before testing and assayed for free T. Relationships between individual T concentrations and performance were assessed as a pooled group and 4 sub-groups of equal size. RESULTS: As pooled data sets, none of the IMTP and CMJ performance variables were significantly correlated with free T in either the PF or PP groups (r=0.01-0.23). The PF and PP abilities of the 4 sub-groups were significantly different, so that PF1>PF2>PF3>PF4 (P<0.001) and PP1>PP2>PP3>PP4 (P<0.01). When the 4 sub-groups were analysed, the T concentrations of the PF4 group were significantly (P<0.05-0.01) correlated to PRFD (r=0.69) and F100 ms (r=0.55) during the IMTP, as was F100 ms in the PF1 group (r=0.66). In the PP1 group, free T also correlated to CMJ height (r=0.62). CONCLUSION: The key conclusion is that the expression of force and power in an elite athletic group may be dependent, to some extent, on individual variation in salivary free T concentrations and existing strength or power levels. The current results also confirm that the grouping of elite athletes of mixed strength or power ability may bias predictive results in a manner not reflective of sub-groups within this population.

Scaling strength and power for body mass differences in rugby union players.

AIM: This study on professional rugby union players was undertaken to: 1) confirm a relationship between body mass (BM) and peak force (PF) and peak power (PP); 2) evaluate the effect of ratio and allometric scaling on these relationships; and 3) compare the PF and PP abilities of different positional groups with each approach. METHODS: Seventy-nine rugby players were assessed for PF during an isometric mid-thigh pull and/or countermovement jump PP. Athlete performance was normalized for BM using standard ratio and allometric scaling methods. The performance data from inside backs (IB), outside backs (OB), tight forwards (TF) and loose forwards (LF) were compared before and after scaling for BM. RESULTS: Significant relationships were identified between BM and the absolute expression of PF (r=0.25) and PP (r=0.44). These relationships improved with the application of ratio scaling (r=-0.53 to -0.57), but were eliminated after allometric scaling with the derived exponents (r=0.00-0.02). No positional group differences in absolute and allometrically scaled PF and PP were seen, but ratio scaled performance favoured the lighter IB and OB over the heavier TF and/or LF (P<0.05). CONCLUSION: The PF and PP abilities of professional rugby union players were related to individual BM and these relationships were differentially affected by ratio (enhanced) and allometric (removed) scaling. Ratio scaled performance favoured the lighter backs over the heavier forwards, which could be explained by their specific movement patterns within a game. Comparing positional data in such a manner may help practitioners to better quantify, assess and monitor the position-specific needs of athletes in team sport.

Validating two systems for estimating force and power.

This study examined the validity of 2 kinematic systems for estimating force and power during squat jumps. 12 weight-trained males each performed single repetition squat jumps with a 20-kg, 40-kg, 60-kg and 80-kg load on a Kistler portable force plate. A commercial linear position transducer (Gymaware [GYM]) and accelerometer (Myotest® [MYO]) were attached to the bar to assess concentric peak force (PF) and peak power (PP). Across all loads tested, the GYM and MYO estimates of PF and PP were moderately to strongly correlated ( P≤0.05-0.001) with the force plate measurements ( R=0.59-0.87 and R=0.66-0.97), respectively. The mean PF and PP values were not significantly different between the 2 kinematic systems and the force plate, but the estimates did produce some systematic bias and relatively large random errors, especially with the 20-kg load (PF bias >170 N, PF error >335 N, PP bias >400 W, PP error >878 W). Some proportional bias was also identified. In summary, the estimation of PF and PP by a linear position transducer and accelerometer showed moderate to strong relative validity and equivalent absolute validity, but these estimates are limited by the presence of bias and large random errors.

Dynamics of the ventilatory response in man to step changes of end-tidal carbon dioxide and of hypoxia during exercise.

1. Four human subjects exercised in hypoxia (end-tidal partial pressure of O2 (P(ET),O2) ca 55 Torr; heart rate ca 100-130 beats min-1), and the contribution to the respiratory drive of the peripheral and central chemoreflex pathways have been separated on the basis of the latencies and the time courses of the responses to sudden changes of stimulus. 2. The subjects were exposed to repeated end-tidal step changes in PCO2 of ca 3-3.5 Torr (at nearly constant P(ET),O2) and PO2 (between ca 55 and 230 Torr) at three regions along the expiratory ventilation VE-P(ET),CO2 response line (hypocapnia, eucapnia, hypercapnia). The dynamics of the ventilatory responses were calculated using a two-compartment non-linear least-squares optimization method. 3. The component of the response attributable to the peripheral chemoreflex loop may in some subjects contribute up to 75% of the ventilatory drive during mild hypocapnic hypoxic exercise and ca 72% of the total gain following steps of P(ET),CO2 during hypoxic exercise. These data support the notion that the effectiveness of the peripheral chemoreceptor pathway is enhanced in moderate exercise. 4. During hypoxic exercise, the time delays and time constants attributed to the peripheral chemoreflex pathways (ca 3.5 and 9 s respectively) and to the central chemoreflex pathways (ca 9.5 and 47 s respectively) are some of the shortest reported. 5. The dynamics of the peripheral and central chemoreflex pathways appeared to be largely independent of each other. 6. There was a notable absence of systematic change of inspiratory and expiratory durations during the step-induced transients.

Analyses of human respiratory flow patterns.

Respiratory drives follow various afferent pathways to the respiratory centres; nevertheless, steady-state breathing patterns described in terms of tidal volumes and phase durations are largely independent of the nature of the respiratory stimulus. Flow has now been recorded during steady states from six subjects in rest and hyperpnoea induced by exercise, and hypercapnia in euoxia and in hypoxia (asphyxia). Flow patterns from different stimuli were compared isopnoeically. Quantitative methods allowed the patterns to be described in terms of several variables. The consistent small differences in isopnoeic flow patterns were: In asphyxia, the initial inspiratory acceleration was greater than in hypercapnia, and the peak flow was reached earlier. In exercise the peak flow occurred later in inspiration, and the expiratory flow was maintained high until nearer the end of the phase than with the chemical drives so that the flow pattern was less angular in shape. Stimulus-dependent effects, obvious during transient changes, are greatly attenuated rather than absent in steady states.

Patterns of breathing in response to alternating patterns of alveolar carbon dioxide pressures in man.

The time profile of alveolar PCO2 within the respiratory cycle has been forced to follow contrasting patterns in alternate breaths, in two different ways. Within-breath changes (w.b.c., with a CO2-rich inspirate supplied early or late in alternate inspirations) involved minimal alternation of end-tidal PCO2. Between-breath changes (b.b.c., with whole inspirates of CO2-free or CO2-rich gas) involved large swings of end-tidal PCO2. As previously reported (Metias, Cunningham, Howson, Petersen & Wolff, 1981), both patterns of forcing were associated with alternation of ventilation, but only when hypoxia was present. The patterns of the alternating reflex responses in 118 runs on four human subjects in steady hypoxia are described in terms of alternation of inspiratory and expiratory tidal volume, time and mean flow. These patterns often disappeared, or changed unpredictably in mid-run. The inspiratory pattern of reflex alternation depended in part on the type of forcing, but alternation of inspiratory tidal volume was usually observed with both types. No single pattern of expiratory alternation emerged as predominant. The pattern of reflex expiratory alternation was surprisingly independent of the pattern of inspiratory alternation: indeed, in w.b.c., but not in b.b.c., alternation of mean expiratory flow and of mean inspiratory flow were mutually exclusive. It is concluded that in man, as in cats and dogs, the arterial chemoreceptor pathway has access to various parts of the respiratory pattern generator, the exact response depending to some extent on the timing within the respiratory cycle. In particular, expiratory variables may be influenced directly through the arterial chemoreceptor pathway, i.e. without any supposedly mediating inspiratory alternation being demonstrable. The results are discussed briefly in relation to some current views on the organization of respiratory control.

The pattern of breathing in man in response to sine waves of alveolar carbon dioxide and hypoxia.

Sine waves of alveolar CO2 at constant high alveolar O2, and sine waves of alveolar hypoxia (1/(PA, O2 -C) where C congruent to 32 torr) at constant alveolar CO2 have been administered to three subjects in each case. Six different periods of the sine waves were studied, ranging between 900 and 30 s for the CO2 sine waves and 300 and 20 s for the hypoxic sine waves. The sinusoidal variations in inspiratory and expiratory volumes (VT, I, VT, E), durations (TI, TE) and mean flows (vI, vE) produced by these manoeuvres were calculated, and the results analysed from the phase shifts of the responses. For the CO2 sine-wave results, the peak in the TI oscillation generally appeared after the minima for VT, I and vI, but before their maxima. The peak in the TE oscillation was variable. For the hypoxic sine-wave results, the peak in the TI oscillation showed no over-all tendency to lead or lag the peaks of VT, I and vI. The peak in the TE oscillation generally appeared after the maxima for VT, E and vE but before their minima. For the CO2 sine-wave results, expiratory mean flow led inspiratory mean flow, with the volumes showing no significant difference. For the hypoxic sine-wave results expiratory volumes and mean flows led inspiratory volumes and mean flows. The results are discussed in relation to the transient responses of the components of breathing pattern obtained from other perturbations of chemical drive.

Malignant melanoma of the foot.

This discussion and case presentation demonstrate the importance of proper diagnostic procedures when a suspect lesion presents. Biopsy and examination by a pathologist in the field of malignant melanoma revealed an immediate definitive diagnosis. Any delay of such measures will increase the chance of metastasis and the degree of necessary surgical excision.

The short-latency respiratory response to sudden withdrawal of hypercapnia and hypoxia in man.

Five healthy young male subjects were maintained in a state of mild asphyxia (PA, CO2 approximately 45 torr, 6.0 kPa, PA, O2 approximately 50 torr, 6.6 kPa), i.e. with moderately strong drives from both arterial and intracranial chemoreceptors VT, TT and TI were recorded and V and TE derived breath by breath. The arterial chemoreceptor component was briefly and abruptly reduced, perhaps silenced, by two separate procedures, each repeated twenty-four times on each subject: B, removal of hypercapnia (two breaths hypoxia with PI, CO2 = 0 through a separate inspiratory line) and C, removal of asphyxia (two breaths O2). In control tests, A, the maintenance mixture was replaced by an identical mixture, using an identical manipulation. For each subject means of B and C were compared with means of A and with each other. Quick reflex changes (first three breaths) in V, VT and TE in tests B were not appreciably different from those in tests C in any subject; changes in TI were minimal in all. Thus removal of only the hypercapnic component of the arterial chemoreflex drive appears to be as efficient as the removal of both components simultaneously.

Reflex effects on human breathing of breath-by-breath changes of the time profile of alveolar PCO2 during steady hypoxia.

The respiratory effects of forced changes of alveolar PCO2 were studied in four healthy human subjects and in one anaesthetized cat. Solenoid valves, triggered by changes in mouth pressure, allowed changes from one inspiratory gas mixture to another, either during expiration (between-breath changes, BBC) or in the middle of inspiration (within-breath changes, WBC). In BBC the subject breathed CO2-free gas in one inspiration, CO2-rich gas in the next, and so on; end-tidal PCO2 alternated regularly from breath to breath by 1.1 kPa. In WBC CO2-free gas was given early in one inspiration and late in the next, with CO2-rich gas late in the former and early in the latter, and so on end-tidal PCO2 was nearly constant from breath to breath. Eight respiratory output variables were analysed. WBC induced small but significant alternation in most of the variables; these effects occurred almost exclusively in runs in hypoxia. The responses were not very different from those seen in BBC. The experiment on the cat showed that the alveolar PCO2 changes predicted during WBC are reflected by changes in pH in the arterial blood. The results confirm predictions based upon observations in the steady state of tube- and reversed-tube breathing in man. It seems likely that the responses are mediated by the arterial chemoreceptors responding to small changes in the profile of the (CO2, H+) oscillation.