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.

Drug prescribing for hypertension at primary healthcare facilities in Trinidad.

OBJECTIVE: To describe the drug prescribing pattern for hypertension at primary healthcare facilities throughout Trinidad. METHODS: A descriptive, cross-sectional survey was conducted at 22 primary healthcare facilities across Trinidad using a de novo, pilot-tested questionnaire during June to August 2006. RESULTS: A total of 547 hypertensive patients were recruited into the study. There was a high prevalence of diabetes mellitus (57.6%). Information on the current drug prescribed was available for 442 patients (80.0%) and 26 of these patients (6.1%) were managed without drug intervention. On average, patients were prescribed 1.47 antihypertensive drugs. Angiotensin converting enzyme (ACE) inhibitors, particularly enalapril, were the most commonly prescribed class of antihypertensive drugs in 63.6% of patients. beta-blockers, thiazide diuretics and calcium channel blockers were prescribed in 29.2%, 25.8% and 12.0% of patients respectively. CONCLUSIONS: There was significant use of ACE inhibitors, beta-blockers, thiazide diuretics and calcium channel blockers. Angiotensin converting enzyme inhibitors (as monotherapy or in combination with other drug classes) were more likely to be prescribed in diabetic hypertensive patients. Thiazide diuretics were not used as frequently as expected given the evidence which demonstrate similar efficacy with other classes of drugs and associated cost-saving. The observed prescribing pattern in the Trinidad public healthcare setting seems to point to an attempt to conform to recognized international and regional guidelines for the management of hypertension.

Drug prescribing for hypertension at primary health care facilities in Trinidad / Prescripción de medicamentos para la hipertensión en los centros de atención primaria de lasalud en Trinidad

OBJECTIVE: To describe the drug prescribing pattern for hypertension at primary healthcare facilities throughout Trinidad. METHODS: A descriptive, cross-sectional survey was conducted at 22 primary healthcare facilities across Trinidad using a de novo, pilot-tested questionnaire during June to August 2006. RESULTS: A total of 547 hypertensive patients were recruited into the study. There was a high prevalence of diabetes mellitus (57.6%). Information on the current drug prescribed was available for 442 patients (80.0%) and 26 of these patients (6.1%) were managed without drug intervention. On average, patients were prescribed 1.47 antihypertensive drugs. Angiotensin converting enzyme (ACE) inhibitors, particularly enalapril, were the most commonly prescribed class of antihypertensive drugs in 63.6% of patients. ß-blockers, thiazide diuretics and calcium channel blockers were prescribed in 29.2%, 25.8% and 12.0% of patients respectively. CONCLUSIONS: There was significant use of ACE inhibitors, ß-blockers, thiazide diuretics and calcium channel blockers. Angiotensin converting enzyme inhibitors (as monotherapy or in combination with other drug classes) were more likely to be prescribed in diabetic hypertensive patients. Thiazide diuretics were not used as frequently as expected given the evidence which demonstrate similar efficacy with other classes of drugs and associated cost-saving. The observed prescribing pattern in the Trinidad public healthcare setting seems to point to an attempt to conform to recognized international and regional guidelines for the management of hypertension.

OBJETIVO: Describir el patrón de prescripción de medicamentos para la hipertensión en los centros de atención primaria de la salud en Trinidad. MÉTODOS: Se llevó a cabo un estudio descriptivo transversal en 22 centros de atención primaria de la salud en Trinidad, aplicando un cuestionario de novo en prueba piloto de junio a agosto de 2006. RESULTADOS: Un total de 547 pacientes hipertensos fueron reclutados para este estudio. Hubo una alta prevalencia de diabetes mellitus (57.6%). La información sobre el medicamento corriente prescrito estuvo disponible para 442 pacientes (80.0%) y 26 de estos pacientes (6.1%) fueron tratados sin la intervención del medicamento. Como promedio, a los pacientes se les prescribieron 1.47 medicamentos antihipertensivos. Los inhibidores de la enzima convertidora de angiotensina (IECA), en particular el enalapril, fueron la clase de medicamentos antihipertensivos más comúnmente prescritos en el 63.6% de los pacientes. Los beta-bloqueadores, los diuréticos tiazídicos, y los bloqueadores de los canales de calcio, fueron prescritos en el 29.2%, 25.8% y 12.0% de los pacientes respectivamente. CONCLUSIONES: Hubo un uso significativo de inhibidores ECA, beta-bloqueadores, diuréticos tiazídicos, y bloqueadores de los canales de calcio. Los inhibidores de la enzima convertidora de angiotensina (en forma de monoterapia o en combinación con otras clases de medicamentos) exhibían una probabilidad mayor de ser prescritos en los casos de pacientes diabéticos hipertensos. Los diuréticos tiazídicos no se usaron con tanta frecuencia como se esperaba, dada las evidencias existentes que demostraban una eficacia similar con otras clases de medicamentos, asociados con un menor costo. El patrón de prescripción observado en el contexto de la salud pública en Trinidad parece apuntar a un intento por ajustarse a las pautas regionales e internacionales reconocidas en relación con el tratamiento de la hipertensión.