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R B Jordan

Publications and source records attributed to R B Jordan.

At least 19 recordsLinked to original sources
PubMed2006

First hydrolysis constants of hexaaquacobalt(III) and -manganese(III): longstanding issues resolved.

The acid dissociation constants, Kh, of the hexaaquacobalt(III) and -manganese(III) ions are reported under conditions which minimize the problems of instability of these species at modest acidities (pH 1-4). A rapid and convenient preparation of aqueous Co(III) has been used, and the latter has been reacted with aqueous Mn(II) to form aqueous Mn(III). The noncoordinating buffer H2PIPPS (1,4-bis(3-sulfopropyl)piperazine) has been used to react with H+ and provide some control of the pH. Spectrophotometric changes, after stopped-flow mixing for Co(III) and conventional mixing for Mn(III), were used to determine the Kh values. The pKh values are as follows: Co(III), 3.10 +/- 0.07 (6.0 degrees C) and 2.92 +/- 0.04 (20.0 degrees C) in 1.0 M H+, Na+, ClO4-; Mn(III), 0.22 +/- 0.04 (7.6 degrees C) and 0.08 +/- 0.04 (20.0 degrees C) in approximately 4 M H+, Mn2+, ClO4-. Global fits of the data for each metal have been used to estimate the DeltaH degree and DeltaS degree values for Kh. It is suggested that the unusually high acidity of Mn(OH2)6(3+) may be due to a Jahn-Teller distortion effect.

Journal Article↗
PubMed2004

Linkage isomerism, structure, and reactivity studies of sulfenamide complexes of cobalt(III).

The S-bonded sulfenamide isomers have been prepared by the known reaction of hydroxylamine-O-sulfonate with (en)(2)Co(III) thiolate complexes of aminoethanethiol, cysteine, and penicillamine and the cis dithiolate formed by N,N'-ethylene-di-penicillamine (EDP) and Co(III). It is shown that the sulfenamides undergo linkage isomerization in alkaline solution to produce their respective N-bonded linkage isomers. The addition of acid yields the protonated N-bonded isomers. The structures of [(en)(2)Co(NH(2)S(CH(2))(2)NH(2))](2)(S(2)O(6))(3) and [Co((NH(2)S)(2)EDP)]Br have been determined by X-ray crystallography, and the pK(a) of [(en)(2)Co(NH(2)S(CH(2))(2)NH(2))](3+) has been determined by spectrophotometry. The pH dependencies of the kinetics of the linkage isomerization reactions have been studied and yield pK(a) values of the S-bonded isomers. The (en)(2)Co systems give only the acid-stable N,N' isomer at equilibrium, whereas the EDP complex gives a mixture of N,N' and N,S isomers at pH 7-9.

Cobalt↗
PubMed2003

Copper-63 NMR line width study of the copper(I)-acetonitrile system.

The principal focus of this study is the (63)Cu NMR line widths in Cu(I)-acetonitrile (AN) solutions. The variations with the concentrations of Cu(I) salts (trifluoromethanesulfonate and perchlorate), added salts, water, chloride ion, and temperature have been studied. A quantitative analysis shows that the anomalous temperature dependence of the line widths is not due to ion pairing or anion complexation but results primarily from formation of a species with a different coordination number or less symmetrical arrangement of AN ligands than in the normal tetrahedral Cu(AN)(4)(+) ion. Solvent viscosity and ion pairing (with triflate) also are identified as factors having the expected effects on the line widths. The results of earlier studies also are discussed and analyzed by the current model where possible.

Journal Article↗
PubMed2002

Kinetic study of the oxidation of catechol by aqueous copper(II).

The kinetics of the oxidation of catechol by aqueous copper(II) have been studied as a function of reactant concentrations at pH 6.4-7.2. To follow the reaction, a spectrophotometric method has been developed that circumvents the problem of precipitation of decomposition products of the initial o-quinone oxidation product. The rate law shows that the reactive species is the monocatecholate complex of Cu(II), and that this species undergoes rate-limiting intramolecular electron transfer with k = 1.9 x 10(-5) s(-1) (22 +/- 1 degrees C, mu = 0.125 M NaClO(4)). The results have allowed a reanalysis of previous work on the autoxidation in the aqueous Cu(II)-catechol-dioxygen system, and comparisons to mechanisms of copper(II) oxidases.

Journal Article↗
PubMed2002

Formation constants of copper(I)-olefin complexes in aqueous solution.

A simple kinetic method has been applied to measure the formation constants of aqueous copper(I) with fumaronitrile, dimethyl fumarate, and fumaric and maleic acids. At 0.14 M ionic strength, the values of beta(1) are (0.85 +/- 0.02) x 10(3), (6.1 +/- 0.1) x 10(3), (7.3 +/- 0.1) x 10(3), and (2.2 +/- 0.4) x 10(3) M(-1), respectively. The values for the last two olefins are compared to previous results. Values of beta(1) for hydrogen maleate and beta(2) for fumaronitrile also have been determined. A reanalysis of much earlier work has been done, and all the results are discussed in terms of the effect of substituents on the olefin on the beta(1) values. The structure of bis(fumaronitrile)copper(I) nitrate also is reported. The nitrile is N-coordinated to copper(I), which has a distorted tetrahedral geometry, while the overall structure consists of macrocyclic Cu(6)(fumaronitrile)(6) rings which extend in three dimensions.

Journal Article↗
PubMed2001

Complex formation constants for the aqueous copper(I)-acetonitrile system by a simple general method.

A simple spectrophotometric method for the evaluation of formation constants for aqueous copper(I) has been developed, based on the kinetics of reduction of Co(III)(NH(3))(5)X complexes. The method has been applied to the aqueous copper(I)-acetonitrile system to determine the successive formation constants beta(1), beta(2), and beta(3) as 4.3 x 10(2) M(-)(1), 1.0 x 10(4) M(-)(2), and 2.0 x 10(4) M(-)(3), respectively, in 0.14 M NaClO(4)/HClO(4) at 21 +/- 1 degrees C.

Journal Article↗
PubMed2000

Splints and scar management for acute and reconstructive burn care.

Because patients assume a position of comfort during acute burn management, affected joints or regions must be splinted in positions of function to avoid contractures. Particularly with the increasing trend towards ambulatory burn care, close monitoring by the burn team and patient education is required to achieve the best functional result. Despite adequate initial care, contractures sometimes occur, requiring a shift in splinting tactics to correct the deformity. If secondary reconstruction is required, the affected region is once again maintained in the position of function. Although the physiologic mechanism is incompletely defined, pressure therapy to prevent and treat hypertrophic burn scars is an integral component of burn care. Multiple materials and methods are available with treatment, starting soon after burn wound closure, and modified as needed until scar maturation has occurred.

Arm Injuries↗
PubMed1995

Comparison of the morbidity associated with maxillary fractures treated by maxillomandibular and rigid internal fixation.

OBJECTIVE: To compare the type and incidence of morbidity encountered by two groups of patients with maxillary fractures, one treated by closed reduction and maxillomandibular fixation and the other by open reduction and rigid internal fixation. STUDY DESIGN: This was a retrospective review of records for all patients with maxillary fractures treated over a 10-year period. Age, sex, mechanism of injury, anatomic location of fracture, treatment modality, and complications were identified. Two populations of patients, those treated with closed reduction and maxillomandibular fixation and those treated with open reduction and rigid internal fixation, that were similar in size (n = 50), age, sex, and anatomic distribution of fractures were compared. RESULTS AND CONCLUSIONS: This study indicates that patients with maxillary fractures treated with either closed reduction and maxillomandibular fixation or open reduction and rigid internal fixation will encounter postoperative problems with a near equal frequency (60% to 64%). Regardless of the technique used, no relationship could be established between age, sex, or cause of injury. The more superior the level of the fracture, the higher the rate of adverse sequelae.

Adolescent↗
PubMed1993

Limb- and life-threatening desmoid tumor of the neck.

The treatment of extraabdominal desmoid tumors remains controversial. Although a radical resection is associated with lower recurrence rates, the treatment of extensive, limb-threatening, or multifocal desmoids may require a more conservative excision with postoperative radiation and selective hormonal therapy. This approach would minimize functional deficits and improve cosmesis. If conservative resection with adjuvant radiotherapy and endocrine manipulation has failed and the tumor is compromising vital functions, then more radical resections may be justified.

Adult↗
PubMed1990

Long saphenous vein grafts as an aid to microsurgical reconstruction of the trunk.

The authors describe a method of closing truncal defects using free-tissue transfer when neither local tissue or vascular access are available. The long saphenous vein is dissected free as far distally as necessary and turned up, leaving its upper drainage intact. The distal end is then anastomosed to the femoral artery to create a temporary arteriovenous loop. After placing an appropriate free flap in the defect, the A-V loop is divided and used to provide both arterial supply and venous drainage for the flap. Anatomy, technique, and representative cases in which this method has been used for closing traumatic tissue defects of the trunk are presented and discussed.

Abdominal Muscles↗
PubMed1988

Cervical teratomas: an analysis. Literature review and proposed classification.

Cervical teratomas are uncommon lesions usually diagnosed at birth but occasionally reported in older children and adults. During a 58-year span, nine cervical teratomas were identified at our institution (four previously reported): three stillborns with giant tumors; five live newborns; and one adult with a malignant tumor. Of the five newborns, two prematures died within one hour of birth. Of the three survivors, 2 had respiratory distress at birth. These infants were treated with early excision and are well at 7, 6, and 2 years of age. The last patient also had cystic fibrosis. The adult died of metastatic disease 8 months after resection. A literature review disclosed 212 cases in addition to the five reported here. Previous attempts at categorizing cervical teratomas have failed to address clinical patterns and have little prognostic value. We propose a classification based on birth status, age at diagnosis, and the presence or absence of respiratory distress. Group I--stillborn and moribund live newborns: number (N), 27; mortality (M), 100%. Group II--newborn with respiratory distress: N, 99; M, 43.4%. Group III--newborn without respiratory distress: N, 37; M, 2.7%. Group IV--children age 1 month to 18 years: N, 31; M, 3.2%. Group V--adults: N, 23; M, 43.5%. Twenty-six patients in group II and one in group III died without excision of the mass. Seventy-three patients in group II, 36 in group III, and 31 in group IV had extirpation of the tumor. Operative mortality was 11%, 0%, and 3.2%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗