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D R Cole

Publications and source records attributed to D R Cole.

At least 19 recordsLinked to original sources
PubMed2007

Novel corresponding-states principle approach for the equation of state of isotopologues: H2(18)O as an example.

The corresponding-states principle (CSP) has been considered for the development of the equations of state (EOS) of minor isotopologues that are usually unknown. We demonstrate that, for isotopologues of a given molecular fluid, a general extended multi-parameter corresponding-states EOS can be reduced to the three-parameter EOS, utilizing the critical parameters (temperature and density) and Pitzer's acentric factor as correlation parameters. Appropriate general CSP mathematical formalism and equations for constructing the EOS of minor isotopologues are described in detail. The formalism and equations were applied to isotopologues of water and demonstrated that the isotopic effect on the critical parameters and the acentric factor of H(2)(18)O can be successfully calculated from the EOS of H2O and experimental data on the isotope effects (liquid-vapor isotope fractionation factor and molar volume isotope effect). We have also shown that the experimental data on the vapor pressure isotope effect (VPIE) for 18O-substituted water are inconsistent within the framework of thermodynamics with the liquid-vapor oxygen isotope fractionation factor. The novel approach of CSP to isotopologues developed in this study creates a new opportunity for constructing the EOS of minor isotopologues for many other molecular fluids.

Journal Article↗
PubMed2006

Quasielastic neutron scattering study of dynamics of CaCl2 aqueous solution confined in Vycor glass.

Quasielastic neutron scattering was used to probe the diffusion of water molecules in 2.3 molal CaCl(2) solution confined in 100% hydrated Vycor glass in the temperature range of 220 to 260 K. We observed a gradual transition from the restricted diffusion regime at lower temperatures to unrestricted diffusion regime at higher temperatures. The diffusion parameters were compared with the data on pure water confined in Vycor available in the literature. We found that the effect of dissolved ions onto the diffusion dynamics of the water molecules in the solution was amplified by confinement by at least an order of magnitude compared to bulk form, even though the dissolved ions were found to have little effect on the spatial characteristics of the restricted diffusion process of water molecules. At 260 K, the local diffusion coefficient of water molecules in the H(2)O-CaCl(2) confined in Vycor was only 6% of the value reported for pure water confined in Vycor.

Calcium Chloride↗
PubMed2006

Adsorption of supercritical CO2 in aerogels as studied by small-angle neutron scattering and neutron transmission techniques.

Small-angle neutron scattering (SANS) has been used to study the adsorption behavior of supercritical carbon dioxide (CO2) in porous Vycor glass and silica aerogels. Measurements were performed along two isotherms (T=35 and 80 degrees C) as a function of pressure (P) ranging from atmospheric up to 25 MPa, which corresponds to the bulk fluid densities ranging from rho(CO2) approximately 0 to 0.9 gcm3. The intensity of scattering from CO2-saturated Vycor porous glass can be described by a two-phase model which suggests that CO2 does not adsorb on the pore walls and fills the pore space uniformly. In CO2-saturated aerogels an adsorbed phase is formed with a density substantially higher that of the bulk fluid, and neutron transmission data were used to monitor the excess adsorption at different pressures. The results indicate that adsorption of CO2 is significantly stronger in aerogels than in activated carbons, zeolites, and xerogels due to the extremely high porosity and optimum pore size of these materials. SANS data revealed the existence of a compressed adsorbed phase with the average density approximately 1.07 gcm3, close to the density corresponding to closely packed van der Waals volume of CO2. A three-phase model [W. L. Wu, Polymer 23, 1907 (1982)] was used to estimate the volume fraction phi3 of the adsorbed phase as a function of the fluid density, and gave phi3 approximately 0.78 in the maximum adsorption regime around rho(CO2) approximately 0.374 gcm3. The results presented in this work demonstrate the utility of SANS combined with the transmission measurements to study the adsorption of supercritical fluids in porous materials.

Journal Article↗
PubMed2005

Effect of temperature on the adsorption of water in porous carbons.

We report experimental and simulation studies to investigate the effect of temperature on the adsorption isotherms for water in carbons. Adsorption isotherms are measured by a gravimetric technique in carbon-fiber monoliths at 378 and 423 K and studied by molecular simulation in ideal carbon pores in the temperature range 298-600 K. Experimental adsorption isotherms show a gradual water uptake, as the pressure increases, and narrow adsorption-desorption hysteresis loops. In contrast, simulated adsorption isotherms at room temperature are characterized by negligible uptake at low pressures, sudden and complete pore filling once a threshold pressure is reached, and wide adsorption-desorption hysteresis loops. As the temperature increases, the relative pressure at which pore filling occurs increases and the size of the hysteresis loop decreases. Experimental adsorption-desorption hysteresis loops are narrower than those from simulation. Discrepancies between simulation and experimental results are attributed to heterogeneities in chemical composition, pore connectivity, and nonuniform pore-size distribution, which are not accounted for in the simulation model. The hysteresis phase diagram for confined water is obtained by recording the pressure-density conditions that bound the simulated hysteresis loop at each temperature. We find that the hysteresis critical temperature, i.e., the lowest temperature at which no hysteresis is detected, can be hundreds of degrees lower than the vapor-liquid critical temperature for bulk model water. The properties of confined water are discussed with the aid of simulation snapshots and by analyzing the structure of the confined fluid.

Journal Article↗
PubMed2005

Isotopic self-exchange reactions of water: evaluation of the rule of the geometric mean in liquid-vapor isotope partitioning.

Deviations from the random distribution of hydrogen isotopes among isotopic species of liquid and vapor water (the rule of the geometric mean) were critically assessed theoretically and experimentally from the triple to critical point of water. A third-order polynomial equation of the classical near-critical expansion was used to accurately describe the liquid-vapor isotope fractionation of H2O and D2O on the basis of their equations of state. It was found that experimental data for the enthalpy of mixing of H2O-D2O can be used to calculate accurately the deviation from the rule of the geometric mean in liquid and vapor water, ln(KD(v)/KD(l)). A new equation obtained in this study shows that the value of ln(KD(v)/KD(l)) smoothly decreases from +0.009 to 0 with increasing temperature from the triple to critical temperature of water. In contrast, the equation available in the literature and that derived from mass spectrometric measurements of liquid-vapor partitioning of H2O and HDO show complex behavior, including maximum, minimum, and crossover.

Journal Article↗
PubMed2004

Density fluctuations near the liquid-gas critical point of a confined fluid.

We report the results of an experimental study of the effect of a dilute silica network on liquid-gas critical phenomena in carbon dioxide (CO2). Using small-angle neutron scattering, we measured the correlation length of the density fluctuations in bulk (xi(bulk)) and confined CO2 (xi(conf)) as a function of temperature and average fluid density. We find that quenched disorder induced by an aerogel suppresses density fluctuations: xi(conf) loses the Ising model divergence characteristic of xi(bulk) and does not exceed the size of pores in the homogeneous region.

Journal Article↗
PubMed2004

The New Zealand Diabetes Passport Study: a randomized controlled trial of the impact of a diabetes passport on risk factors for diabetes-related complications.

AIMS: To assess the efficacy (change in HbA1c) of a patient-held communication, self-empowerment and educational device for people with diabetes (the New Zealand Diabetes Passport) in patients with poor glycaemic control. RESEARCH DESIGN AND METHODS: A 12-month, multicentre, general practice-based randomized controlled trial in urban, provincial and rural New Zealand involving 398 people with poorly controlled Type 1 or Type 2 diabetes. The intervention included a specifically designed and piloted New Zealand Diabetes Passport including information relating to diabetes knowledge, self-assessments, and guidance concerning how to engage with diabetes health professionals. The primary end point was change in HbA1c. Assessments were made at 0, 6 and 12 months. RESULTS: Two hundred and twenty-two patients received the Passport, 176 the control booklet, coming from 69 and 66 general practitioners, respectively. Use of the Passport was associated with a relative reduction in HbA1c of 0.4% (P = 0.017) and a relative increase in weight of 1.0 kg/m2 (P = 0.028), but no changes in diabetes knowledge, attitudes to diabetes or risk factors for diabetic tissue damage. CONCLUSIONS: The dissemination of the New Zealand Diabetes Passport, in isolation, was not associated with improvements in either diabetes knowledge or self-empowerment. While a small improvement in glycaemic control occurred, this was probably due to changes in insulin therapy in the intervention group. It is possible that linking the use of the Passport with other behavioural and educational interventions may make the Passport more useful. Further study is required to confirm the effect of such multifaceted interventions.

Body Weight↗
PubMed2000

A screening approach to the surveillance of patients with diabetes for the presence of vision-threatening retinopathy.

OBJECTIVE: To provide scientifically based screening rules for the primary care setting designed to identify, through evaluation of a prescribed and limited portion of the posterior fundus, those patients with diabetes who have retinopathy severe enough to need referral to eye care specialists. DESIGN: Retrospective analysis of the Early Treatment Diabetic Retinopathy Study (ETDRS) photographic data base. PARTICIPANTS: The fundus photographic grading data from 3711 patients with diabetes enrolled in the ETDRS. METHODS: Multivariate regression techniques were used to identify retinopathy lesions in photographic fields 1, 2, 3, or a combination thereof that predict proliferative diabetic retinopathy (PDR) or clinically significant macular edema (CSME) within the seven standard fields. These were used to construct a family of screening rules with optimal combined sensitivity and specificity on which to base referrals to eye care specialists. MAIN OUTCOME MEASURES: Presence of moderate to severe nonproliferative diabetic retinopathy (NPDR), PDR, or CSME in graded fundus photographs. RESULTS: Hemorrhages and microaneurysms (h/ma) temporal to the macula (photographic field 3), as severe as or more severe than ETDRS standard photograph 1 (h/ma 3 > or = 3), identified 87% to 89% of eyes with PDR and 92% to 93% of eyes with moderately severe to severe NPDR, which are at high risk for developing PDR. Extrapolating the results using retinopathy prevalence data from epidemiologic studies for the general older onset diabetic population, the calculated sensitivity for detecting PDR on a single examination is 87%, the specificity 80%; for moderate NPDR or worse, the sensitivity is 81 %, specificity 93%. Applying the presence of h/ma 3 > or = 3 as a screening rule to the older onset population, 26.5% of patients would be referred and 73.5% would not be referred. Any hard exudate within one disc diameter of the macular center detects CSME with sensitivity 94%, specificity 54%. Hard exudate of moderate or worse severity anywhere in the macular region (field 2) predicts CSME with sensitivity 89%, specificity 58%. CONCLUSIONS: Screening protocols based on assessing retinopathy lesion severity in the posterior fundus have the potential to identify most diabetic patients with vision-threatening retinopathy. If the protocols can be implemented effectively in a primary care setting, patients requiring referral for specialty care could be reliably identified, and the total number of patients needing specialty referral could be substantially reduced from current guidelines.

Diabetes Mellitus↗
PubMed1995

Ethical considerations with African-American elders.

African American elders are a diverse group whose values and beliefs are part of the ethics of United States society. The interplay between these beliefs and the health care system offers many challenges for the geriatrician. Addressing issues of autonomy, beneficence, nonmaleficence, truth-telling, confidentiality, and justice are important in caring for African American elders.

Black or African American↗
PubMed1995

A good wife, but never a mother....

Prolactinomas are the commonest pituitary tumour. They are more frequent in women and account for up to 15% of patients with amenorrhoea (through secondary gonadotrophin suppression). Here we present two patients with previously unrecognized giant prolactinomas, one of whom is probably unique in having radiological evidence of progression from micro to macro prolactinoma in the absence of treatment. Both were being considered for hormone replacement therapy. These tumours are known to be oestrogen sensitive and potentially life threatening. Both had been investigated for amenorrhoea prior to the availability of prolactin assays; no other cause had been found. Amenorrhoeic patients investigated prior to the early 1970s should be reviewed with this in mind. Patients with untreated microprolactinomas should probably be monitored indefinitely.

Amenorrhea↗
PubMed1994

Serum biopterin--a novel marker for immune activation during pre-diabetes in the BB rat.

Tetrahydrobiopterin (BH4) is a pteridine product which is released by rodent macrophages on activation by cytokines. We have used serial pancreatic biopsy, and measurement of serum biopterin at 30, 60, 90 and 120 days in the BB/S rat to relate histological change to macrophage activation during the course of pre-diabetes. Using immunohistochemistry, and an arbitrary scoring system read blind and standardised against day 30, we found that pancreatic MHC class I, MHC class II and infiltrating macrophage staining were up-regulated in the BB/S diabetes-prone rats (n = 17) at day 60, markedly so at day 90, and less so at day 120. Staining for resident pancreatic macrophages remained unchanged throughout in diabetes prone, diabetes resistant and Wistar (n = 28) control animals. Serum biopterin fell progressively and identically with age in BB diabetes resistant rats (n = 11) and Wistar controls. No change in weight gain or biopterin levels was observed in the biopsied animals. Mean serum biopterin levels in diabetes prone rats (of which 13 of 17 became diabetic at median 85 days) were the same as in diabetes resistant and Wistar rats at days 30, 60 and 120, but showed a striking and highly significant elevation (p < 0.001) at day 90. Although macrophages infiltrate the islet early in pre-diabetes, the timing of their activation is unknown. The rise in biopterin we observed is a potentially important immunological event which occurred late in the progression of pre-diabetes. This acute terminal event has not been reported previously, and may modify current concepts concerning the tempo of cell destruction during pre-diabetes.

Aging↗
PubMed1993

Metabolic control in streptozotocin diabetic rats following transplantation of microencapsulated pancreatic islets.

Microencapsulated islet grafts implanted into the peritoneal cavity of a variety of animal models of diabetes have been shown to reverse hyperglycaemia over prolonged periods without immunosuppression. Here, effects of these grafts on intermediary metabolites, diurnal blood glucose and glycated haemoglobin were studied in streptozotocin-diabetic Wistar rats. Following transplantation (approximately 3000 islets) glucose and the ketone 3-hydroxybutyrate fell significantly (glucose: 19.1 +/- 0.6 (SD) to 9.2 +/- 4.3 mmol/l, p < 0.01; 3-hydroxybutyrate: 1.51 +/- 0.48 to 0.55 +/- 0.38 mmol/l, p < 0.02) and remained within/close to the normal range for at least four weeks. In control diabetic animals, values remained abnormally elevated. There was no difference in lactate, alanine or glycerol between the two groups. In transplanted animals there was a marked variation in blood glucose over a 24h period, values being low during daylight hours but with nocturnal peaks (up to 25 mmol/l) during the animals' normal feeding time. Glycated haemoglobin was also lower in transplanted animals but did not return to normal and the difference was not significant. In conclusion, microencapsulated islet grafts ameliorated the diabetic state. However, normal metabolic homeostasis was not achieved. The intraperitoneal site precludes direct graft vascular access and this may be a contributory factor. Additionally, daytime blood sugar values in murine models of diabetes may be a poor guide to graft function and glucose tolerance.

3-Hydroxybutyric Acid↗
PubMed1992

Microencapsulated islet grafts in the BB/E rat: a possible role for cytokines in graft failure.

Alginate-polylysine microencapsulation has been proposed as a method of protecting transplanted pancreatic islets against immunological attack. Using this technique, prolonged graft survival has been reported in some diabetic animals. However, in the spontaneously diabetic insulin-dependent BB/E rat we found that intraperitoneal implantation of microencapsulated islets had only a short-lived effect on hyperglycaemia. Recovered microcapsules (both those implanted empty and containing islets) were surrounded by a foreign body type cellular overgrowth and, although many capsules remained intact, encapsulated islets were observed to be disintegrating. Loss of Beta cells was confirmed by immunohistology. Various polymer materials used in artificial membranes have been shown to activate macrophages involved in foreign body reactions and induce synthesis of interleukin-1 beta, a known Beta-cell toxin. Reduced secretion of insulin and progressive islet damage (indicated by a significant reduction in residual islet insulin and DNA content) were demonstrated when microencapsulated islets were incubated with interleukin-1 beta in vitro for 9 days. Similar effects were seen following exposure to a combination of gamma interferon and alpha tumour necrosis factor. Successful use of microencapsulation in islet transplantation depends upon the development of biocompatible membranes. The exclusion of smaller molecules, such as cytokines, which may be involved in foreign body mediated damage and microencapsulated islet graft rejection, could also be important.

Alginates↗
PubMed1992

Dermatitis artefacta. Case reports.

Patients who seek care for foot problems may present to the podiatrist with concurrent problems, such as anxiety, depression, phobias, personality disorders, and psychoses. These may or may not have any direct relationship to the pathogenesis of the foot problem. The podiatrist may learn of the presence of an emotional problem directly from the patient or from a family member. In many cases, the patient may be unaware or deny the presence of an emotional problem, leaving the podiatric physician in the dark about the patient's mental health state or its implications for the management of the skin problem. In a review of the psychosomatic aspects of dermatology, Koblenzer offered a working classification of the psychodermatoses. This is helpful to the podiatrist in recognizing those dermatologic disease states in which the various aspects of the individual participate in the disease, signs and symptoms of the disease, and the potential psychological value of the disease for the patient. It is also helpful to the podiatrist for recognizing those dermatoses in which psychiatric consultation may be useful so that recognition, treatment, improvement, and perhaps cure may be effected quickly.

Adolescent↗
PubMed1992

Systemic complications of human immunodeficiency virus infection.

HIV infection causes a wide spectrum of complications affecting all organ systems. These complications may be primary to the direct infection of a specific organ system by HIV or secondary to the immunodeficiency associated with HIV infection. These complications may be specific to certain stages of HIV infection. Selected common complications of HIV infection include pulmonary, neurologic, GI, dermatologic, oral, ocular, endocrine, and hematologic complications.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Resolving problems in the physician's office.

Obviously, physicians prefer to use their office hours practicing medicine, therefore, they may tend to overlook these administrative functions. In today's busy practice, finding time to review procedures often is difficult. However, an office error becomes wholly the responsibility of the physician when it leads to a misdiagnosis or failure to diagnose. Periodic review of office procedures may help improve patient care and avoid litigation.

Malpractice↗
PubMed1988

Von Hippel-Lindau disease in a large British family: clinicopathological features and recommendations for screening and follow-up.

We describe the clinical and pathological features in nine members of a large British family with von Hippel-Lindau disease. Twenty living family members underwent detailed assessment for features of the disease, including retinal examination and computed tomography of the head and abdomen. The hospital records of three deceased family members were reviewed and detailed information about a fourth was obtained from members of the family. As a result of this study, three asymptomatic family members were found to have features of the disease and all three living affected family members were found to have additional features. Lesions discovered included retinal angiomas requiring treatment in four family members, one asymptomatic renal cell carcinoma and one asymptomatic pancreatic endocrine tumour. We also report the occurrence of a spermatic cord mesenchymal hamartoma in von Hippel-Lindau disease.

Adolescent↗