On the generation of solar spicules and Alfvénic waves.

In the lower solar atmosphere, the chromosphere is permeated by jets known as spicules, in which plasma is propelled at speeds of 50 to 150 kilometers per second into the corona. The origin of the spicules is poorly understood, although they are expected to play a role in heating the million-degree corona and are associated with Alfvénic waves that help drive the solar wind. We compare magnetohydrodynamic simulations of spicules with observations from the Interface Region Imaging Spectrograph and the Swedish 1-m Solar Telescope. Spicules are shown to occur when magnetic tension is amplified and transported upward through interactions between ions and neutrals or ambipolar diffusion. The tension is impulsively released to drive flows, heat plasma (through ambipolar diffusion), and generate Alfvénic waves.

Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares.

The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds) of intensity and velocity on small spatial scales (≲500 kilometers) at the footpoints of hot and dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of nonthermal electrons, which are generated in small impulsive (≲30 seconds) heating events called "coronal nanoflares." The accelerated electrons deposit a sizable fraction of their energy (≲10(25) erg) in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.

Hot explosions in the cool atmosphere of the Sun.

The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection.

Prevalence of small-scale jets from the networks of the solar transition region and chromosphere.

As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~10(5) kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.

The unresolved fine structure resolved: IRIS observations of the solar transition region.

The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle.

On the prevalence of small-scale twist in the solar chromosphere and transition region.

The solar chromosphere and transition region (TR) form an interface between the Sun's surface and its hot outer atmosphere. There, most of the nonthermal energy that powers the solar atmosphere is transformed into heat, although the detailed mechanism remains elusive. High-resolution (0.33-arc second) observations with NASA's Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere and TR that are replete with twist or torsional motions on sub-arc second scales, occurring in active regions, quiet Sun regions, and coronal holes alike. We coordinated observations with the Swedish 1-meter Solar Telescope (SST) to quantify these twisting motions and their association with rapid heating to at least TR temperatures. This view of the interface region provides insight into what heats the low solar atmosphere.

The origins of hot plasma in the solar corona.

The Sun's outer atmosphere, or corona, is heated to millions of degrees, considerably hotter than its surface or photosphere. Explanations for this enigma typically invoke the deposition in the corona of nonthermal energy generated by magnetoconvection. However, the coronal heating mechanism remains unknown. We used observations from the Solar Dynamics Observatory and the Hinode solar physics mission to reveal a ubiquitous coronal mass supply in which chromospheric plasma in fountainlike jets or spicules is accelerated upward into the corona, with much of the plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK) and a small but sufficient fraction to temperatures above 1 MK. These observations provide constraints on the coronal heating mechanism(s) and highlight the importance of the interface region between photosphere and corona.

Chromospheric alfvenic waves strong enough to power the solar wind.

Alfvén waves have been invoked as a possible mechanism for the heating of the Sun's outer atmosphere, or corona, to millions of degrees and for the acceleration of the solar wind to hundreds of kilometers per second. However, Alfvén waves of sufficient strength have not been unambiguously observed in the solar atmosphere. We used images of high temporal and spatial resolution obtained with the Solar Optical Telescope onboard the Japanese Hinode satellite to reveal that the chromosphere, the region sandwiched between the solar surface and the corona, is permeated by Alfvén waves with strong amplitudes on the order of 10 to 25 kilometers per second and periods of 100 to 500 seconds. Estimates of the energy flux carried by these waves and comparisons with advanced radiative magnetohydrodynamic simulations indicate that such Alfvén waves are energetic enough to accelerate the solar wind and possibly to heat the quiet corona.

Clopidogrel increases expression of chemokines in peripheral blood mononuclear cells in patients with coronary artery disease: results of a double-blind placebo-controlled study.

BACKGROUND: Chemokines and platelet activation are both important in atherogenesis. Platelet inhibitors are widely used in coronary artery disease (CAD), and we hypothesized that the platelet inhibitor clopidogrel could modify chemokines in CAD patients. OBJECTIVES: We sought to investigate the effect of clopidogrel on the expression of chemokines and chemokine receptors in peripheral blood mononuclear cells (PBMC) in CAD patients. PATIENTS/METHODS: Thirty-seven patients with stable angina were randomized to clopidogrel (n = 18) or placebo (n = 19). PBMC, blood platelets and plasma were collected at baseline and after 7-10 days in the patients, and in 10 healthy controls. mRNA levels of chemokines and chemokine receptors in PBMC were analyzed by ribonuclease protection assays and real-time reverse transcriptase polymerase chain reaction. Platelet activation was studied by flow cytometry. RESULTS: (i) At baseline, the gene expression of the regulated on activation normally T-cell expressed and secreted (RANTES) chemokines and macrophage inflammatory peptide (MIP)-1beta in PBMC, the expression of CD62P and CD63 on platelets and the levels of platelet-derived microparticles (PMP) were elevated in angina patients comparing healthy controls; (ii) markers of platelet activation were either reduced (CD63) or unchanged (CD62P, PMP, beta-thromboglobulin) during clopidogrel therapy; (iii) in contrast, clopidogrel significantly up-regulated the gene expression of RANTES and MIP-1beta in PBMC, while no changes were found in the placebo group; (iv) a stable adenosine 5'-diphosphate metabolite attenuated the release of MIP-1beta, but not of RANTES, from activated PBMC in vitro. CONCLUSIONS: Even if we do not argue against a beneficial role for clopidogrel in CAD, our findings may suggest potential inflammatory effects of clopidogrel in CAD.

[Prevention of cardiovascular disease in type 2 diabetes]. / Forebygging av hjerte- og karsykdom ved type 2-diabetes.

BACKGROUND: Patients with type 2 diabetes have a high risk of morbidity and premature mortality from cardiovascular disease. Epidemiological studies show that many of the risk factors are the same as in non-diabetic subjects. At present there are sufficient data in the literature to recommend prophylactic measures to be initiated in diabetic patients. MATERIAL AND METHODS: We review major studies relevant for prophylactic measures against cardiovascular disease in patients with type 2 diabetes, and suggest Norwegian recommendations. RESULTS: All patients should be advised to adhere to a healthy life style including an appropriate diet, physical exercise and no smoking. Treatment of hyperglycaemia is primarily indicated in order to improve quality of life and reduce the risk of microvascular complications, as it still remains to be proven if glucose lowering therapy may protect against macrovascular disease. Pharmacological prophylactic therapy with acetylsalicylic acid, anti-hypertensive agents and lipid lowering drugs are indicated in high-risk patients. IMPLICATIONS: Several pharmacological and non-pharmacological interventions may protect type 2 diabetic patients from premature cardiovascular morbidity and mortality. Anti-hypertensive treatment may protect diabetic patients both from microvascular and macrovascular disease and premature death.

[Current use of beta-blockers in coronary artery disease]. / Aktuell bruk av beta-blokkere ved koronar hjertesykdom.

This article presents the results of a retrospective analysis of the use of beta-blockers and current dosing of these agents in patients with coronary artery disease. While 70 to 78% of patients admitted to Norwegian university hospitals during 1990-1997 for angiographic evaluation of chest pain used beta-blockers, only 43-60% of patients with stable coronary artery disease enrolled in the 4S study in Norway received such treatment. High risk groups such as diabetics and patients with peripheral artery disease were less likely to receive beta-blockers during the early period, but were not treated differentially compared to low risk patients during recent years. Only 15% of patients with congestive heart failure received oral beta-blockers, and only 10.5% intravenous beta-blockade during acute myocardial infarction. The dosing of the most common beta-blockers were low, approximately 50% of doses shown to improve survival after acute myocardial infarction.

[The heart bridge. A follow-up study of cardiac patients from the health region 1 operated abroad during the period 1985-87]. / Hjertebroen. Etterundersøkelse av hjertepasienter fra helseregion 1 operert i utlandet i årene 1985-87.

During the years 1985 to 1987 a total number of 388 patients from the Norwegian health region 1 were transferred from Ullevål Hospital to heart centres abroad for heart operation because of the low operating capacity in our own hospital. The operative mortality in pure coronary bypass operations was 6.0%. Six out of 34 patients (17.6%) died postoperatively following valvular replacements. A questionnaire was sent to all survivors in November, 1989 and July, 1996. The clinical condition was judged to be very good or good by 95% and 83% of the patients, respectively. A self-evaluation of quality of life on a visual analog scale indicated a significant improvement after the operation.

Comparative effects of long-acting and conventional propranolol on stress-induced angina pectoris and on frequency of ventricular premature beats.

Ten male patients with chronic stable angina pectoris completed a randomized, double-blind cross-over study, with matched placebo run-in period (P), to compare the effects of a long-acting preparation of propranolol (LA, 160 mg once a day) with that of conventional propranolol (CP, 40 mg four times a day) each given for 14 days. Response was assessed by symptom-limited bicycle ergometry, degree of ST segment depression, daily anginal attack rate and glyceryl trinitrin consumption (GTN). Heart rate and ventricular extra-systolic frequency (VES) were recorded by 24 h Holter monitor. Bicycle ergometry was performed and a trough blood sample taken for propranolol estimation on day 14 prior to the morning dose. Both formulations increased total work capacity (P 3412, LA 4095, CP 3697 kpm/min), reduced rate-pressure product (P 21896, LA 16011, CP 15609 mm Hg beats/min), and degree of ST segment depression (P 4.53, LA 2.48, CP 2.43), but without differences between the formulations. Daily anginal attack rate was reduced from 30 (placebo) to 7.5 (CP) and 14.5 (LA) (P less than 0.05 between treatment groups). There was a reduction in daily GTN consumption by both treatments. The heart rate and total number of VESs during 24 h was similar in the two treatment groups and was reduced in comparison with placebo. Both formulations were well tolerated. Long-acting propranolol is an effective and well-tolerated alternative to conventional propranolol in the treatment of chronic stable and stress-induced angina, and in reducing VES frequency.

Beta blockade after myocardial infarction: the Norwegian propranolol study in high-risk patients.

A randomized, double-blind, placebo-controlled trial of propranolol was carried out in 560 high-risk survivors of myocardial infarction enrolled at 12 Norwegian hospitals. The main purpose of the study was to determine the effect of propranolol, 160 mg/day, on the incidence of sudden cardiac death over 12 months. The patients were randomized 4-6 days after the acute event. A statistically significant reduction in sudden cardiac deaths of 52% was noted (11 deaths in the propranolol group and 23 in the placebo group). Four placebo patients and one propranolol patient were successfully resuscitated from ventricular fibrillation. In addition, less severe ventricular arrhythmias were significantly more common among the placebo-treated patients. Twenty-five patients in the treatment group and 37 in the control group died (p = 0.11). Severe adverse effects of the drug were uncommon in this high-risk population. The findings support the results of the Beta-Blocker Heart Attack Trial and other long-term beta-blocker trials in survivors of myocardial infarction.

One year's treatment with propranolol after myocardial infarction: preliminary report of Norwegian multicentre trial.

A prospective, randomised, double-blind study was performed to compare the effects of propranolol and placebo on sudden cardiac death in a high-risk group of patients who survived acute myocardial infarction. Altogether 4929 patients with definite acute myocardial infarction were screened for inclusion: 574 (11.6%) died before randomisation, and 3795 (77%) were excluded. Five hundred and sixty patients aged 35 to 70 years were stratified into two risk groups and randomly assigned treatment with propranolol 40 mg four times a day or placebo. Treatment started four to six days after the infarction. By one year there had been 11 sudden deaths in the propranolol group and 23 in the placebo group (p less than 0.038, two-tailed test analysed according to the "intention-to-treat" principle). Altogether there were 25 deaths in the propranolol group and 37 in the placebo group (P less than 0.12), with 16 and 21 non-fatal reinfarctions respectively. A quarter of the patients were withdrawn from each group. Withdrawal because of heart failure during the first two weeks of treatment was significantly more common among propranolol-treated patients than among the controls, but thereafter the withdrawal rate was the same. The significant reduction in sudden death was comparable with that after alprenolol, practolol, and timolol, which suggests that the mechanism of prevention is beta-blockade rather than any other pharmacological property of the individual drugs.