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A new low density mineral material has been synthesized via a simple, flexible, cheap and easy to control process. This material is a synthetic carbonate produced by carbonation of a solid phase composed of a calcic part and a magnesian part. Typically, its production process includes the calcination of a raw dolomite (general formula CaCO3.MgCO3) into the oxide form, followed by an at least partial hydration of this oxide and a subsequent carbonation step. This process is thus close to the well-known process used for the production of Precipitated Calcium Carbonate (PCC), a common filler and pigment in plastic, paper and rubber, except that the raw material is a dolomite instead of a limestone. It has to be pointed out that flue gases from different industries can be used as a source of CO2 for the carbonation. Many parameters have been studied, such as the hydration conditions or the carbonation conditions, allowing the production of a whole range of products. The products obtained via this process are composed of a calcic part, mainly as calcite and aragonite (CaCO3), and a magnesium containing part, mainly as hydromagnesite (4MgCO3.Mg (OH)2.4H2O). Compared to standard PCC, this material has a particularly low density (100-250 kg/m3 instead of 300-600 kg/m3 for standard PCC), a rather high BET specific surface area (15-35 m2/g instead of 4-15 m2/g for standard PCC) and a specific particle morphology and structure. The particles are indeed commonly spherical particles composed of a core of calcite/aragonite covered by a layer of hydromagnesite. This structure can be described as a core-shell structure. Due to these special features, this product could be used in multiple applications, such as raw material for the manufacture of insulation material, flame retardant, filler in plastics, paints, paper, rubber, and many more.

To determine whether fetal compensatory renal growth occurs in response to early gestational unilateral renal obstruction and to help elucidate the characteristics of this response, a fetal lamb model was developed in which unilateral ureteral obstruction was created at 60 days of gestation (term 135 to 140 days) and the effects of the obstruction were studied at varying periods thereafter. Kidneys were retrieved at 2 weeks (75 days in 3 cases), 5 weeks (95 days in 4) and 10 weeks (135 days in 9) after obstruction, weighed and preserved for histology and biochemical studies. Deoxyribonucleic acid (DNA), ribonucleic acid and protein were quantitated using standard assays. Morphometric studies to estimate glomerular number were performed using standard stereological methods. Contralateral kidney weight was increased compared to normals in 55 cases at all ages. The relative difference increased from 75 to 95 days. The fractional increase at 135 days (49.5%, p0.001 versus normal) was not different from 95 days (46.4%, p = 0.87), indicating that growth rate acceleration occurred predominantly before 95 days. Total renal DNA was increased above normal at each time point, with an ultimate increment proportionate to weight. Protein concentration was unchanged, suggesting that weight increase was not due to changes in renal water. Protein/DNA ratios were unchanged, indicating a predominantly hyperplastic process. Ribonucleic acid/DNA ratios decreased, possibly indicating a high rate of proliferation. Total glomerular number at term did not increase with in utero compensatory renal growth. Unilateral ureteral obstruction created early in gestation produced compensatory renal growth of the intact kidney in the fetal lamb. This process demonstrates an early but transient growth rate acceleration, hyperplasia and no increase in total glomerular or nephron number. The occurrence of compensatory renal growth in the fetal kidney with minimal functional renal demand would suggest that its mechanisms may be independent of functional demand. This model is unique and well suited to study compensatory renal growth.

cquired fistulas between the esophagus and tracheobronchial tree are uncommon. The majority of these fistulas occur in patients A with a malignancy and represent a complication of the underlying disease. Although fistulas due to trauma [2] or infection [ 1, 31 have been successfully treated, because of the uniformally fatal outcome in those patients with acquired esophagotracheobronchial fistulas due to malignancy, surgeons have been reluctant to attack them. The development of such a fistula undoubtedly leads to the earlier death of the patient. Furthermore, the morbidity associated with any communication between the esophagus and tracheobronchial tree is distressing both to the patient and to the physician. It seems that a more aggressive approach should be taken by surgically treating certain selected patients with a tracheoesophageal fistula caused by a malignancy. In this paper the cases of acquired esophagotracheobronchial fistulas seen at The Johns Hopkins Hospital from 1927 through 1964 will be briefly reviewed, and 3 cases of successful treatment of this condition in patients with a malignancy will be reported. REVIEW OF CASES

A study has been conducted immediately and up to 18 days after the surgical production of complete heart block in dogs. Immediately after surgery cardiac output, coronary flow, and mean arterial pressure were reduced in rough proportion to the degree of bradycardia. In time, these measures began to return toward preoperative levels. Paralleling the diminished left ventricular work was a diminished left ventricular oxygen consumption with little consequent change in myocardial efficiency. Small rises were detected in central venous pressure. At autopsy, the only unequivocal abnormality was myocardial hypertrophy which became measurable between 2 and 18 days after operation.

Direct cardiac stimulation was conducted in the open chest. In normal animals, auricular stimulation at frequencies faster than the spontaneous rate caused little change in vascular pressures or cardiac output. Comparable ventricular stimulation in the same animals caused falls in cardiac output and blood pressure, with elevations in venous pressure. In contrast, ventricular stimulation in animals with complete heart block caused elevations in cardiac output and blood pressure, and declines in venous pressure. A study was also made of repetitive stimulation in experimental cardiac arrest. Occasionally pacemaking was of value in the resuscitation, but in most cases effective contractions could not be induced with stimulation.

The hemodynamic changes resulting from injection of radiopaque material into the left heart in a series of patients undergong cineangiographic studies have been reported. The hypertonicity of radiopaque materials appears to be responsible for much of the observed reaction. The mechanism whereby hypertonic solutions produce the observed physiologic changes remains unknown. Changes observed in patients could be reproduced in experimental animals. The combined experimental and clinical data show that left atrial pressure increases, left atrial pulse contour alters, stroke output increases, heart rate is much unchanged, peripheral artery pressure falls, hematocrit level falls, and myocardial contractile force decreases mildly and transiently. The difference between the physiologic effects of injecting hypertonic media into the right and left sides of the circulation is discussed. Because the pressure changes are easy to monitor and parallel the other features of the hemodynamic reaction, it is good to wait until pressures have returned to the pre-angiographic level before proceeding with the injection of more radiopaque material. This usually requires 15 minutes.

The incidence of ventricular fibrillation is increasing because of the large number of thoracic and cardiac procedures being performed. Many cases of ventricular fibrillation occur in one year in a large hospital and several times in one week in cardiac centers. Although the incidence of ventricular fibrillation is greater during operations on the chest, it may occur during any operative procedure and with any anesthetic agent. Consequently, it is important that the members of every operating team be able to treat ventricular fibrillation and standstill and that every suite of operating rooms have an electrical defibrillator. The defibrillator should be simple in design and easy to operate and should deliver what appears at this time to be the optimal voltages at the optimal durations. The apparatus should be so constructed as to safeguard both the patient and the operating room personnel; of necessity, therefore, it must be explosion-proof. Because none

Labeling erythrocytes with radioactive chromium (Cr51) has made possible study of the fate of normal and diseased erythrocytes.1The ability of the spleen to sequester red blood cells has been demonstrated in numerous pathological states, the most prominent of which are hereditary spherocytosis, certain autoimmune hemolytic anemias, cirrhosis of the liver, and Gaucher's disease. In an effort to determine why some red cells are destroyed in the spleen while others are not, Harris, McAlister, and Prankerd studied the sites of destruction of red cells with both induced and naturally occurring abnormalities.2Spherocytes produced by heating red cells for 15 minutes at 50 C and red cells whose surface lipids had been reduced by alumina were selectively sequestered in the spleen after injection. Red cells in which metabolism had been inhibited by incubation in sodium arsenate were destroyed in areas other than the spleen. An extensive series of