Single-well injection-withdrawal tests as a contaminant transport characterisation tool for landfilled waste

A new single well injection withdrawal (SWIW) test was trialled at four landfills using the tracers lithium and deuterium, and by injecting clean water and measuring electrical conductivity. The aim of the research was to develop a practical test for measuring lateral contaminant transport to aid in the design of landfill flushing. Borehole dilution tests using dyes were undertaken prior to each SWIW test to determine background flow velocities. SWIW tests were performed at different scales by varying the volume of tracer injected (1 to 5,800 m³) and the test duration (2 to 266 days). Tracers were used individually, simultaneously or sequentially to examine repeatability and scaling. Mobile porosities, estimated from first arrival times in observation wells and from model fitting ranged from 0.02 to 0.14. The low mobile porosities measured rule out a purely advective-dispersive system and support a conceptual model of a highly preferential dual-porosity flow system with localised heterogeneity. A dual-porosity model was used to interpret the results. The model gave a good fit to the test data in 7 out of 11 tests (where R² ≥ 0.98), and the parameters derived are compatible with previous experiments in MSW. Block diffusion times were estimated to range from 12 to 6,630 h, with a scaling relationship apparent between the size of the test (volume of tracer used and/or the duration) and the observed block diffusion time. This scaling relationship means affordable small-scale tests can inform larger-scale flushing operations.

Outcome of pediatric inpatient asthma clinical pathway implementation in a military medical center

A performance improvement project was instituted at our facility to standardize pediatric inpatient asthma care by instituting an asthma clinical pathway (ACP). Formal asthma education and standardized postdischarge follow-up plans for all asthma inpatients were initiated. Patients treated by following the ACP were compared against historically similar patients from the previous 4 years. Differences in hospital length-of-stay (LOS) for patients treated on the ACP were compared to historical LOS. Adherence to The Joint Commission's home management plan of care metric, CAC-3, was also compared. There was a 25% lower hospital LOS in the ACP group compared to historical control group, 45.8 hours versus 60.9 hours (p < 0.002). CAC-3 adherence significantly increased from 48% to 89% (p < 0.001) after initiating formal asthma education. The implementation of a pediatric asthma inpatient performance improvement project was associated with a significant decrease in hospital LOS, when compared to historic controls. It also led to a significant improvement in adherence with The Joint Commission's CAC-3 measures.

Delayed presentation: negative pressure pulmonary hemorrhage

Negative pressure pulmonary hemorrhage (NPPH) is a rare, life-threatening complication that develops after an acute upper airway obstruction. A 26 year old, healthy African-American man with no underlying lung disease developed negative pressure pulmonary edema and subsequently NPPH during recovery from general anesthesia for elective spine surgery. Diagnostic bronchoscopy confirmed an alveolar source of the bleeding. Clinical improvement was quick with supportive care in the medical intensive care unit.

Incidence, treatment and outcome of rectal stenosis following transanal endoscopic microsurgery

BACKGROUND

As an alternative to more radical abdominal surgery, transanal endoscopic microsurgery (TEM) offers a minimally invasive solution for the excision of certain rectal polyps and early-stage rectal tumours. The patient benefits of TEM as compared to radical abdominal surgery are clear; nevertheless, some drawback is possible. The aim of our study was to determine the risk factors, treatment and outcomes of rectal stenosis following TEM.

METHODS

We analysed a series of 354 consecutive patients who underwent TEM for benign or malignant rectal tumours between 1997 and 2009. We recorded the maximum histological diameter of the lesion, and whether the lesion was circumferential. Rectal stenosis was defined as a rectal narrowing not allowing passage of a 12 mm sigmoidoscope.

RESULTS

Histological results with a measured specimen diameter were available in 304 of the 354 cases. There were 11 stenoses in total (3.6%), 7 stenoses due to 9 circumferential lesions (78%) and 4 due to lesions with a maximum diameter ≥ 5 cm (3.2%). Two patients presented as emergencies, and the other 9 patients reported symptoms of increased stool frequency at follow-up. Three of the stenoses were associated with recurrent disease. All stenoses were treated by a combination of endoscopic/radiological balloon dilatation or surgically with Hegar's dilators. A median of two procedures were required to treat stenoses until resolution of symptoms.

CONCLUSIONS

Rectal stenosis following TEM excision is rare. It is predictable in patients with circumferential lesions but is rare in patients with non-circumferential lesions with a maximum diameter ≥ 5 cm. It is effectively treated with surgical or balloon dilatation. Most patients require repeated treatments.

A tracer methodology for identifying ambient flows in boreholes

Identifying flows into, out of, and across boreholes is important for characterizing aquifers, determining the depth at which water enters boreholes, and determining the locations and rates of outflow. This study demonstrates how Single Borehole Dilution Tests (SBDTs) carried out under natural head conditions provide a simple and cheap method of identifying vertical flow within boreholes and determining the location of in-flowing, out-flowing, and cross-flowing fractures. Computer simulations were used to investigate the patterns in tracer profiles that arise from different combinations of flows. Field tracer tests were carried out using emplacements of a saline tracer throughout the saturated length of boreholes and also point emplacements at specific horizons. Results demonstrated that SBDTs can be used to identify flowing fractures at the top and bottom of sections of vertical flow, where there is a change in vertical flow rate within a borehole, and also where there are consistent decreases in tracer concentration at a particular depth. The technique enables identification of fractures that might be undetected by temperature and electrical conductance logging, and is a simple field test that can be carried out without pumping the borehole.

Supralevator fistula-in-ano in tuberculosis

AIM

Perianal Mycobacterium tuberculosis is rare, but tuberculosis (TB) is now endemic in many areas of the world. It is essential to recognize TB to institute appropriate management. We report three cases of TB presenting with supralevator abscess.

METHOD

We analysed the outcomes of three patients who presented to our unit, from 2004 to 2009, with supralevator abscess caused by TB.

RESULTS

The patients presented as emergencies with symptoms of per-anal sepsis. All required multiple drainage procedures. Supralevator extension was confirmed clinically and radiologically (by magnetic resonance imaging in two patients and by computed tomography scanning in one patient). One patient was diagnosed by perianal biopsy, the second by culture of pus and the third by sputum culture. Following drainage, all three patients were given anti-TB medication for 6 months. In all patients, the fistulae had high communication with the anal canal. In one patient, local drainage and medical therapy led to sepsis resolution, the second patient has residual complex fistulae and the third patient has recently commenced antimicrobial therapy.

CONCLUSION

As TB is endemic in many parts of Europe, TB should be suspected in patients with complex and/or recurrent perianal sepsis. Samples for histological and bacteriological analyses should be obtained from these patients. Recurrent perianal drainage procedures are likely to be required, and sepsis may persist after anti-TB therapy.

Generalized diffusion equation for anisotropic anomalous diffusion

Motivated by studies of comblike structures, we present a generalization of the classical diffusion equation to model anisotropic, anomalous diffusion. We assume that the diffusive flux is given by a diffusion tensor acting on the gradient of the probability density, where each component of the diffusion tensor can have its own scaling law. We also assume scaling laws that have an explicit power-law dependence on space and time. Solutions of the proposed generalized diffusion equation are consistent with previously derived asymptotic results for the probability density on comblike structures.

Redistribution of contaminants by a fluctuating water table in a micro-porous, double-porosity aquifer: field observations and model simulations

Large seasonal fluctuations of the water table are characteristic of aquifers with a low specific yield, including those fractured, double-porosity aquifers that have significant matrix porosity containing virtually immobile porewater, such as the Chalk of northern Europe. Where these aquifers are contaminated, a strong relationship between water table elevation and contaminant concentration in groundwater is commonly observed, of significance to the assessment, monitoring, and remediation of contaminated groundwater. To examine the processes governing contaminant redistribution by a fluctuating water table within the 'seasonally unsaturated zone', or SUZ, profiles of porewater solute concentrations have been established at a contaminated site in southern England. These profiles document the contaminant distribution in porewater of the Chalk matrix over the SUZ at a greater level of detail than recorded previously. A novel double-porosity solute transport code has been developed to simulate the evolution of the SUZ matrix porewater contaminant profiles, given a fluctuating water table, when the groundwater is initially contaminated and the SUZ is initially free of contamination. The model is simply characterised by: the matrix-fracture porosity ratio, the matrix block geometry, and a characteristic diffusion time. De-saturation and re-saturation of fractures is handled by a new approximation method. Contaminant accumulates in the upper levels of the SUZ, where it is less accessible to mobile groundwater, and acts as a persistent secondary source of contamination once the original source of contamination has been removed or has become depleted. The 'SUZ process' first attenuates the progress of contaminants in groundwater, and subsequently controls the slow release of contamination back to the mobile groundwater, thus prolonging the duration of groundwater contamination by many years. The SUZ process should operate in any fractured, micro-porous lithology e.g. fractured clays and mudstones, making this approach widely applicable.

Acute splenic rupture in an adult with homozygous sickle cell anemia treated with chronic transfusions

Splenic rupture is a very rare event in adult homozygous sickle cell patients. The authors describe a 19-year-old patient with homozygous sickle cell disease who experienced an acute splenic rupture crisis requiring emergent splenectomy. He had been receiving chronic blood transfusions regularly for 7 years secondary to a previous stroke. It is possible that these transfusions contributed to regeneration of splenic red pulp, which allowed a crisis to occur at an advanced age.

Life-threatening upper airway edema caused by a distal rattlesnake bite

A 36-year-old man captured a timber rattlesnake and was accidentally envenomated in the thumb by the severed head. At a local emergency department, hypotension and confusion developed. Facial and glossal edema were also observed. Oxygen was delivered by face mask, and crystalloids and dopamine were administered. Respiratory distress developed with progressive hypoxemia. Intubation was unsuccessful because of massive glossal and epiglottic (laryngeal) edema, and an emergency cricothyrotomy was performed. High-dose antivenom therapy was administered, and mechanical ventilation was started. Recovery was rapid, and the patient was discharged from the hospital a week later. This is the first report of life-threatening upper airway edema caused by snake envenomation not in the vicinity of the head or neck.

Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots

New information on the electron-hole wave functions in InAs-GaAs self-assembled quantum dots is deduced from Stark effect spectroscopy. Most unexpectedly it is shown that the hole is localized towards the top of the dot, above the electron, an alignment that is inverted relative to the predictions of all recent calculations. We are able to obtain new information on the structure and composition of buried quantum dots from modeling of the data. We also demonstrate that the excited state transitions arise from lateral quantization and that tuning through the inhomogeneous distribution of dot energies can be achieved by variation of electric field.

Cytogenetics and the biological basis of sarcomas

Recently, much research has been directed toward gaining a better understanding of sarcoma biology. To accomplish this goal, researchers have focused on characterizing the cytogenetic abnormalities that are detectable by routine karyotyping. With the use of widely-available molecular biologic tools, new information on the genetic abnormalities of sarcomas is rapidly emerging. In addition, physicians are beginning to successfully apply cytogenetic and molecular biologic findings to clinical settings in the form of molecular diagnostic and prognostic tests. Moreover, detailed study of these genetic abnormalities is leading to a better understanding of the molecular pathology of sarcomas, which may eventually lead to better therapy. In this paper, we will review the important new findings on genetic abnormalities in sarcomas, clinical applications of cytogenetic studies, and insight into the biology of sarcomas.

Microcytic anemia with iron malabsorption: an inherited disorder of iron metabolism

Two siblings were identified with severe hypoproliferative microcytic anemia and iron malabsorption, in the absence of any gastrointestinal disorder or blood loss. These children had severe microcytosis (MCV 48 fl, hemoglobin 7.5 g/dl) with decreased serum iron, elevated serum TIBC, and decreased serum ferritin, despite prolonged treatment with oral iron. An iron challenge study with an oral dose of 2 mg/kg elemental iron as ferrous sulfate documented iron malabsorption. After treatment with intravenous iron dextran, there was an absence of the expected reticulocytosis and only a partial correction of the hemoglobin, hematocrit, and microcytosis. The bone marrow was hypocellular with abnormal iron incorporation into erythroid precursor cells. This appears to be a rare form of inherited anemia characterized by iron malabsorption and disordered iron metabolism that only partially corrects after the administration of parenteral iron. These features resemble those found in the microcytic mouse (mk/mk), which also has severe microcytic anemia and iron malabsorption that partially responds to parenteral iron.

Forage characteristics, steer performance, and water quality from bermudagrass pastures fertilized with two levels of nitrogen from swine lagoon effluent

Four .8-ha pastures of bermudagrass (Cynodon dactylon [L.] Pers.) were fertilized with either 456 or 873 kg/ha of nitrogen (N) from swine lagoon effluent (two replicates per treatment) and grazed by steers over two summers. Within each pasture, steers received forage only, an energy source (corn), a mixture of corn and soybean meal, or a mixture of corn and blood meal via electronic Calan feeders. All supplements were offered at a level of 1.36 kg/d, and the soybean meal and blood meal supplements provided similar among quantities of protein. Weight gains were similar among supplemented steers, but supplemented steers gained faster (P < .05) than controls. Nitrogen fertilization level had no effect on steer gains, steer grazing days per hectare, or in vitro dry matter disappearance, NDF, and ADF of clipped forage samples. Plant protein and nitrate ion concentrations were greater (P < .06) in clipped forage samples receiving the higher N application rate. Nitrate ion concentrations were greater in available forage samples from the pastures with the high N application rate. Mean total N and nitrate N concentrations were similar in water samples obtained from monitoring wells for the two N treatments over the 2 yr and there were no year x N interactions. Chloride concentrations were greater (P < .05) and pH and specific conductance were less in water samples collected from the 873 kg than from the 456 kg/ha N treatment. Long-term studies are needed to examine the possible cumulative effects of applying various levels of swine waste to the same land area.

Genotoxic activity of 1-chloromethylpyrene in stomach epithelium in vivo: insensitivity of the stomach scintillation UDS assay

An acknowledged weakness of current testing programmes for genotoxic hazard has been the potential insensitivity of the established mouse bone marrow micronucleus test and rat liver unscheduled DNA synthesis (UDS) assays to direct-acting or short-lived mutagens, which may be consumed at the site of initial contact. In such cases, in vivo test systems sampling tissues such as the skin or the stomach would provide valuable data. To test these principles a stomach UDS assay was evaluated using the potent locally active mutagen 1-chloromethylpyrene (1-CMP). Contrary to expectations, no UDS response was observed 16 h following 1-CMP dosage by oral gavage. To confirm the integrity of the 1-CMP used for the stomach UDS assay, a sample of the stored chemical was re-evaluated in vitro and shown to be still strongly positive in the Ames assay and to have alkylating activity at least 15 min after incubation at stomach acid pH. No UDS response was observed when test dose levels were reduced or when earlier sampling times were used. Other genotoxic endpoints were examined in stomach. 32P-Postlabelling analysis revealed high levels of adduct formation in gastric DNA. An assay utilizing electrophoresis of DNA (the comet assay) showed the occurrence of DNA damage following dosing with 1-CMP in vivo. These positive results confirmed that 1-CMP should be regarded as a potential in vivo genotoxin. The failure to detect a UDS response to 1-CMP in stomach was investigated; a strong UDS response was observed in an in vitro hepatocyte UDS assay of 1-CMP indicating that the rat was capable of repairing 1-CMP-derived DNA adducts. Pretreatment of rats with hydroxyurea depressed the level of incorporation of thymidine into DNA both in negative and positive [methyl-N-nitrosoguanidine (MNNG)] controls. The results of these studies indicated that the protease digestion method employed did not selectively or efficiently sample those cells with any UDS response to 1-CMP or MNNG, and the activity seen for the latter was most likely due to the presence of S phase cells within the digests. As a result of the finding that UDS responses were not demonstrated for the potent direct-acting mutagens 1-CMP and MNNG, the protease digestion/scintillation method for stomach UDS does not appear to have general value in a screening programme for locally active genotoxic agents.

Right upper lobectomy twenty years after left pneumonectomy. Preoperative evaluation and follow-up

Quantitative perfusion lung scanning coupled with spirometry and balloon occlusion of the pulmonary artery supplying the lung to be resected have been used to predict the potential operability of patients being considered for pneumonectomy. These techniques were adapted for the lobar level prior to performing a right upper lobectomy in a 59-year-old man who had undergone a left pneumonectomy 20 years previously. This case demonstrates how physiologic reserve can be predicted in patients who require sequential pulmonary resection.

Tracheal mucosal blood flow responses to autonomic agonists

In lightly anesthetized adult sheep, we determined tracheal mucosal blood flow (Qtr) by measuring the steady-state uptake of dimethyl ether from a tracheal chamber created by an endotracheal tube provided with two cuffs. Qtr normalized for carotid arterial pressure [Qtr(n)] was determined before and after the exposure of the tracheal mucosa to aerosolized phenylephrine (0.25-2.0 mg), isoproterenol (0.05-0.8 mg), and methacholine (2.5-20 mg). The same doses of methacholine were also administered during the intravenous infusion of vasopressin. The measurements were repeated after intravenous pretreatment with the respective antagonists phentolamine, propranolol, and atropine. Mean +/- SE base-line Qtr(n) was 1.2 +/- 0.1 ml.min-1.mmHg-1.10(2). The autonomic antagonists had no effect on mean Qtr(n). Phenylephrine produced a dose-dependent decrease in mean Qtr(n) (-70% at the highest dose), which was blunted by phentolamine, and isoproterenol produced a dose-dependent increase in mean Qtr(n) (40% at the highest dose), which was blocked by propranolol. Methacholine failed to alter mean Qtr(n) even when Qtr was first decreased by vasopressin. We conclude that in lightly anesthetized adult sheep 1) base-line Qtr(n) is not under adrenergic or cholinergic control, 2) a locally administered alpha-adrenergic agonist decreases and beta-adrenergic agonist increases Qtr(n) via specific receptor activation, and 3) a locally administered cholinergic muscarinic agonist has no effect on Qtr(n).

Measurement of airway mucosal perfusion and water volume with an inert soluble gas

The purpose of this study was to develop and validate a new in vivo technique for the measurement of tracheal mucosal blood flow (Qtr) and tissue water volume (VH2O) with an inert soluble gas. The technique was based on the notion that the uptake of dimethyl ether (VDME) from an isolated tracheal segment is governed by VH2O (transient state) and Qtr (steady state). In lightly anesthetized sheep, an endotracheal tube with two cuffs placed 14.5-16.5 cm apart was placed to create a chamber into which dimethyl ether was introduced and from which VDMME into the mucosa was determined with a sensitive pneumotachograph. Mean Qtr was 1.20 ml/min (range 0.87-1.73), and mean VH2O was 1.67 ml (range 1.27-2.26). Qtr correlated with cardiac output but not with body weight or tracheal mucosal surface area determined by He dilution. VH2O did not show a correlation with any of these parameters. The response to selected pharmacological agents suggested that the measurements of Qtr and VH2O are independent of each other and from changes in tracheal diameter. Mean Qtr was 80% of mean tracheal mucosal blood flow measured with radiolabeled microspheres. We concluded that the inert soluble gas method is capable of measuring in vivo the perfusion and a water compartment of the intact tracheal mucosa.

Perceptions of family practice residents toward care of the elderly

Family practice residents were surveyed to determine their perceptions of working with geriatric patients. Three areas were surveyed: residents' views of the elderly, their comparisons of the elderly with younger patients and their ideas of what it would be like to work with elderly patients. The results show that generally residents have positive views of geriatric patients. Residents see the elderly as comparing favorably with younger people. Also, they view the elderly as possessing favorable personality characteristics, such as a sense of humor, preference for independence, flexibility, and being easy to work with. Although residents are positive about working with the elderly, they do feel some ambivalence toward working in stroke-rehabilitation programs, as well as with geriatric patients who have lost contact with reality. Medical educators need to be aware of the perceptions that residents have concerning the geriatric patient, since this type of patient will in the future comprise a larger percentage of the resident's practice.

Knowledge and attitudes of family practice residents toward geriatric patients

The knowledge and attitudes of family practice residents toward geriatric patients was surveyed in eight residencies. Since geriatric care will, in the future, become a more important aspect of the family physician's practice, it is important to ascertain the knowledge and attitude level of physicians in training concerning their geriatric patients. Three aspects of this study indicate serious deficits in the educational background of these residents: the number and quality of courses offered to them is inadequate; they demonstrate a paucity of knowledge concerning the aged; the residents show a low preference for working with the aged. Clearly, medical education should address these needs and deficits.

Hormonal control of lipolysis in perifused adipocytes from diabetic rats

The responsiveness of adipocytes from diabetic rats to lipolytic and antilipolytic stimuli was examined in both an incubation system and a perifusion system. Lipolysis, measured by glycerol release, was initiated with varying concentrations of epinephrine or other agents. Incubated adipocytes prepared from streptozotocin-diabetic rats were more sensitive to low doses of epinephrine than controls, but at higher concentrations of hormone, glycerol release was greater from the control cells. However, maximal lipolytic responses to nonhormonal stimuli, forskolin and methylisobutylxanthine, were clearly greater in incubated adipocytes from diabetic animals. In vivo treatment of both control and diabetic animals with insulin decreased the responsiveness of perifused adipocytes to epinephrine in vitro, further demonstrating the importance of the in vivo hormone levels to lipolytic response of adipocytes. In vitro perifusion with insulin and epinephrine of cells from untreated diabetic animals demonstrated a reduced response to the acute administration of insulin. The interaction of insulin with diabetic adipocytes was further examined by incubating cells with [125I]iodoinsulin and examining the release of intact and degraded hormone during perifusion. The diabetic cells bound more labeled hormone than the control cells, but the release of intact hormone was similar in both types of cells. The diabetic cells, however, released more degraded hormone than did control cells. This suggests that the binding and degradation of insulin in diabetic cells is not impaired and that the decreased responsiveness of these cells to insulin is due to a postreceptor defect. Together these data show that decreased insulin in streptozotocin-diabetes results in increased sensitivity to lipolytic agents. In addition, the diabetes enhances the adipocyte's ability to remove insulin, i.e. increased binding and degradation. Thus, it is likely that the in vitro findings of up-regulation of receptors and increased degradation by the adipocytes are a true reflection of the in vivo insulin deficiency.

The convergence of perturbation expansions in classical statistical mechanics

The most successful theory of liquids is perturbation theory in which the attractive energy is treated as a perturbation on the hard-sphere potential and the canonical partition function expanded in powers of the perturbations. The convergence of perturbation theory in the constant pressure, canonical, and grand canonical ensembles is investigated for a one-dimensional square-well fluid, where the calculations are not too lengthy and where a comparison with exact results can be made. At high temperatures, the convergence is excellent in all three ensembles but, at lower temperatures, the convergence is excellent in the canonical ensemble but only fair in the constant pressure and grand canonical ensembles.

Atomic interactions in argon

The potential energy function for interaction of two argon atoms is determined as closely as possible by fitting a multiparameter potential function to experimental data on molecular beam scattering and second virial coefficients, and to the known long-range interaction coefficients. These data are consistent with a range of potential functions between which gas transport properties do not enable a clear choice to be made. In particular, gas viscosities calculated with any of the potential functions show deviations from experiment which are tentatively ascribed to unexpectedly large slip in the viscosity measurements. Third virial coefficients calculated with allowance for the triple-dipole dispersion three-body interaction are close to experimental values whichever function is used, suggesting that other non-additive interactions must be small. Assuming this, the properties of crystalline argon at 0�K are used to specify a single potential function.

Statistical Mechanics of Almost One-dimensional Systems. II

Previous results on the statistical mechanics of almost one-dimensional systems of molecules or atoms are generalized to allow for the presence of a longitudinally varying external potential energy field. Methods for calculating the local density and higher order distribution functions are described. Equations valid for mixtures of molecules of different kinds are derived. Possible applications of the theor{jtical results are indicated and a detailed application to the twodimensional hard disk system is described.

Statistical Mechanics of Almost One-dimensional Systems

A method is described whereby the classical configuration integral of statistical mechanics can be evaluated with any desired accuracy for almost one� dimensional systems with forces of finite range. The systems contemplated are those in which the molecules or atoms can in any given configuration be ordered serially in such a way that a given molecule may be considered as mteracting only with a definite number of neighbours. This kind of model would be appropriate for example for adsorption of gas molecules in very fine Clipillaries. The results are also of importance in connection ith the " tunnel" model for dense fluids and may have other applications as a basis for approximate treatments of real three�dimell8ional systems.

Reflux in Counter-Current Distribution. I. The Acid-Base Process

A method for separating weak acids or bases is described based on counter-current distribution between an organic solvent and an aqueous phase containing their salts. The process is carried out in a Craig tube system modified to permit solvent flow in both directions. By means of stripping sections the system is run under total or partial reflux. This process is closely analogous to fractional distillation, each tube being equivalent to two theoretical plates. The separation attainable in such a system at equilibrium and the rate of approach to equilibrium are discussed quantitatively and optimum operating conditions evaluated. As an example the separation of o- and p-toluic acids is described.

A New Theory of Fluids: The 'Tunnel' Model

A new method for calculating the thermodynamic properties of liquids and compressed gases is proposed, based on a model in which lines of molecules move almost one-dimensionally in " tunnels ", the walls of the tunnels being formed by neighbouring lines of molecules. This picture is related to the " cell " model, but it is a disordered picture, as is appropriate in a model for fluids, and the problem of the " communal entropy " which besets the cell model, does not arise. The method is applied to the hard-sphere fluid and the calculated pressure/volume isotherm is in very much better agreement with the expected isotherm than either the cell theory or the superposition theory, and also in rather better agreement than the virial expansion truncated after five terms.

Statistics of nearest-neighbour dipole and exchange interactions

High-temperature partition functions for nearest-neighbour dipole and exchange interactions on the simple cubic lattice are calculated as far as the terms in (1/kT)8. The results for the dipole case are used in a qualitative discussion of some aspects of the theory of polar liquids and solutions. The principal conclusions are that slow convergence probably makes the power series approach unsatisfactory in the theory of highly polar liquids, and even more unsatisfactory in the theory of solutions containing highly polar components. A simple evaluation of the averages over orientations of dipoles required in this and similar work is given in Appendix I.

Molecular correlations in Cell Theories of liquids and solutions

The thermodynamic effects of correlations between the motions of molecules in neighbouring cells in the Lennard-Jones and Devonshire cell theory of liquids and solutions are calculated approximately, and found to be sufficiently small to be negligible for many purposes.

Determination of Activity Coefficients from total pressure measurements

A method of least squares is described for calculating activity coefficients from results of total vapour pressure measurements.

Studies on the formation of Graphite-Ferric Chloride complexes: Kinetics of Formation

A study has been made of the kinetics of the diffusion of anhydrous FeC1, in graphite. I t was found that this process can be represented for stages between 50 and 100 per cent. saturation of the graphite and at temperatures in the range 200 to 360 OC by a relation of the type δc/δt = D(δ2c/δr2 + δc/δ/r), providing the diffusion coefficient D is assigned several values for concentrations of occluded FeCl3 above and below a critical concentration. The value of the latter was found to be about two-thirds the saturation concentration of FeCl3 in graphite, this value apparently being the point at which open hexagonal packing of intercalated ferric ions is complete and a closer hexagonal packing commences. Values of the activation energies of occlusion for concentrations above and below two-thirds saturation were found from the relations of corresponding values of diffusion coefficients to temper- ature. The small difference between these activation energies which were of the order of 2 to 3 kcal is attributed to a cancelling of effects, thus the energy necessary to separate carbon lamellae in early stages of occlusion is offset in later stages by hindrance imposed on diffusing molecules by those already occluded. Reduction of particle size of graphite accelerated the occlusion of FeCl3.