PubMed Health⌕ Search

Biomedical subjects

J M Maestre

Publications and source records attributed to J M Maestre.

At least 19 recordsLinked to original sources
PubMed2001

Electronic properties of polyoxometalates: a DFT study of alpha/beta-[XM(12)O(40)](n-) relative stability (M=W, Mo and X a main group element).

Keggin heteropolyanions [XM(12)O(40)](n-) have various isomeric structures, alpha and beta being the most common. Conventionally, the alpha structure appears to be the most stable, but calculations carried out at the DFT level for X = P(V), Si(IV), Al(III), As(V), Ge(IV), and Ga(III) and M = W(VI) and Mo(VI) show that this stability depends on several factors, particularly on the nature of the heteroatom (X) and the total charge of the cluster. In this paper, we apply the clathrate model to the Keggin molecule to carry out a fragment-interaction study to elucidate when and why the traditional relative stability of various isomers can be inverted. The fully oxidized anions that have inverted the traditional stability trend in this series are [AlW(12)O(40)](5-) and [GaW(12)O(40)](5-), both of which contain a third-group heteroatom and an overall charge of -5. beta-isomers are always more easily reduced than alpha-isomers. This experimental observation suggests that reduction favors the stability of beta-isomers and one of the most important results of this study is that the alpha/beta inversion is achieved in most cases after the second reduction. The alpha- and beta-isomers may have different properties because the energy of the LUMO, a symmetry-adapted d(xy)-metal orbital, is different.

Journal Article↗
PubMed2001

Electronic and magnetic properties of alpha-Keggin anions: A DFT study of [XM12O40](n-), (M = W, Mo; X = Al(III), Si(IV), P(V), Fe(III), Co(II), Co(III)) and [SiM11VO40](m- (M = Mo and W).

Calculations based on density functional theory (DFT) have been carried out to investigate the electronic and magnetic properties of the alpha-Keggin anions mentioned in the title. The atomic populations and the distribution of the electron density computed for the studied clusters support the hypothesis that an oxidized Keggin anion is an XO(4)(n-) clathrate inside a neutral M(12)O(36) cage. The energy gap between the band of occupied orbitals, formally delocalized over the oxo ligands, and the unoccupied d-metal orbitals, delocalized over the addenda, has been found to be independent of the central ion. However, substitution of a W or a Mo by V modifies the relative energy of the LUMO and then induces important changes in the redox properties of the cluster. In agreement with the most recent X-ray determination of [Co(III)W(12)O(40)](5-) and with the simplicity of the (183)W NMR and (17)O NMR spectra observed for this anion the calculations suggest that [Co(III)W(12)O(40)](5-) has a slightly distorted T(d ) geometry. For the parent cluster [CoW(12)O(40)](6-) the quadruplet corresponding to the anion encapsulating a Co(II) was found to be approximately 1 eV more stable than the species formed by a Co(III) and 1 e delocalized over the sphere of tungstens. The one-electron reduction of [Co(II)W(12)O(40)](6-) and [Fe(III)W(12)O(40)](5-) leads to the formation of the 1 e blue species [Co(II)W(12)O(40)](7-) and [Fe(III)W(12)O(40)](6-). The blue-iron cluster is considerably antiferromagnetic, and in full agreement with this behavior the low-spin state computed via a Broken Symmetry approach is 196 cm(-1) lower than the high-spin solution. In contrast, the cobalt blue anion has a low ferromagnetic coupling with an S-T energy gap of +20 cm(-1). This blue species is more stable than the alternative reduction product [Co(I)W(12)O(40)](7-) by more than 0.7 eV.

Journal Article↗
PubMed2001

[Major ambulatory surgery in otorhinolaryngology].

In the last years we have witnessed a great increase of major ambulatory surgery procedures in our specialty. Some of them are very common as adenoidectomies, tonsillectomies and also the insertion of transtympanic tubes. Nevertheless there is no agreement about which of the procedures should be realized through AMS. The aim of this work is to do a review on the most important features involved in AMS entlightening what kind of operations can be included i such programmes.

Ambulatory Surgical Procedures↗
PubMed2000

[Ambulatory septoplasty].

The AA. admit that the septoplasty under general anaesthesia is a surgical procedure that can be realized ambulatory, without added risks to patient. With viewpoint they have done a retrospective survey of the whole group of septoplasties performed under general anaesthesia at Torrelavega Hospital (Santander) in two years, between April 1995 and August 1997. The total number of cases amounted 56 (49 men and 7 women), lasting the procedure, more or less, one hour; postanaesthesia recovery also about 86 minutes and the hospital permanence about six hours and a half. Readmitted were 14 cases, because vomiting (7), for laryngeal spasm (2), bleeding (1), retention of urine (1) and other because vertigo (1), fever (1) and headache (1).

Adolescent↗
PubMed1999

[Ambulatory laryngeal microsurgery].

OBJECTIVE: The aim of the present study was to determine if laryngeal microsurgery (LMS) under general anesthesia is a safe and convenient procedure when carried out on an outpatient basis in selected patients. MATERIAL AND METHODS: Seventy-eight adult patients (60 men and 18 women) were scheduled for outpatient LMS under general anesthesia between February 1995 and December 1996. RESULTS: Their age range was 19 to 77 years (mean 48 years). Forty-four (56.4%) were ASA I, 32 (41%) ASA II, and 2 (2.6%) ASA III. Laryngeal biopsy was performed in 40 cases (51.3%), polypectomy in 30 cases (38.5%), excision of Reinke's edema in 5 cases (6.4%), and cyst excision in 3 cases (3.8%). The mean stay in the Day Hospital was 7 hours (range 2.5-10 h). Seven patients (9%) had immediate postoperative complications. Three patients were admitted overnight. No patient had to be readmitted to the hospital after discharge. CONCLUSIONS: Outpatient laryngeal microsurgery is an appropriate and safe alternative to inpatient surgery in carefully selected patients, who are kept under strict observation in the immediate postoperative period.

Adolescent↗
PubMed1995

[Cerebrospinal fluid drainage to protect the spinal cord during surgical repair of thoracoabdominal aortic aneurysm].

Spinal cord injury is a serious complication of aortic cross-clamping during thoracoabdominal aortic surgery. We report the case of a 59-year-old man whose mycotic pseudoaneurysm in the thoracoabdominal aorta was repaired surgically. Cerebrospinal fluid pressure was monitored and the fluid was drained to protect the spinal cord while the aorta was clamped. A 19-G epidural catheter was inserted into the subarachnoid space using a paramedian approach form L2-L3. The aorta was clamped at the thoracic level in the descending distal portion and at the abdominal level above the kidney, for a period of 61 minutes. A total of 65 ml of cerebrospinal fluid was drained. The early postoperative period was uneventful and tubes were removed 40 hours after surgery. The results of neurological examination were normal. One week later the patient developed a respiratory infection, which was followed by multi-organ failure and died 22 days after the operation. We discuss the case and review the various alternatives available for protecting the spinal cord during surgery on the thoracoabdominal aorta.

Aortic Aneurysm↗
PubMed1994

Could the piggyback operation in liver transplantation be routinely used?

OBJECTIVE: To determine if orthotopic liver transplantation with inferior vena cava preservation, performed without using caval cross clamping or venovenous bypass, can minimize hemodynamic instability and low renal perfusion pressure. DESIGN: A prospective case series of 44 consecutive adult orthotopic liver transplantations, with a maximum follow-up of 30 months. SETTING: An institutional university referral center. PATIENTS: Between November 1990 and May 1993, 39 consecutive adult liver transplant recipients underwent transplantation with the following primary diagnoses: alcoholic cirrhosis (n = 23), viral cirrhosis (n = 9), primary biliary cirrhosis (n = 2), Wilson's disease (n = 2), primary sclerosing cholangitis (n = 1), fulminant hepatic failure (n = 1), and secondary hepatic malignant neoplasm (n = 1); five had repeated orthotopic liver transplantation. INTERVENTION: Orthotopic liver transplantations were performed using the piggyback technique, but with placement of the vascular clamp on the inferior vena cava laterally instead of across it so that it remained patent throughout the anhepatic stage. Favorable anatomic conditions in the recipients were not considered; venovenous bypass was not used. MAIN OUTCOME MEASURES: Intraoperative hemodynamic profile, blood loss and replacement, surgical time and complications, and patient survival. RESULTS: No significant hemodynamic changes with lateral clamping and no increases in surgical complications, rate of retransplantation, blood product requirements, or survival rate compared with the standard procedure. CONCLUSION: The piggyback operation could be routinely used in orthotopic liver transplantation.

Adult↗
PubMed1994

Enhancement of opiate analgesia by nimodipine in cancer patients chronically treated with morphine: a preliminary report.

The ability of nimodipine, a calcium-channel blocker, to enhance morphine analgesia and/or modify the development of tolerance was studied in patients with cancer pain who had needed successive increments of morphine for periods ranging from 21 to 780 days. Assessment of daily morphine consumption was the primary effect parameter. Nimodipine succeeded in reducing the daily dose of morphine in 16 of 23 patients (oral, n = 13; intrathecal, n = 3), and failed to modify it in 2 patients. Total oral daily dose was reduced by nimodipine (120 mg/day) from 282.6 +/- 47.7 mg to 158.7 +/- 26.2 mg (n = 15, P < 0.001). Intrathecal morphine was also reduced by 1-5 mg/day. Nimodipine was withdrawn in 5 patients during the first week of treatment due to intolerance (n = 3) or aggravation of the disease (n = 2). These preliminary results support experimental findings showing that pharmacological interference with Ca(2+)-related events may modify chronic opioid effects, including the expression of tolerance.

Administration, Oral↗
PubMedDate not supplied

[Heart rupture following thoracic blunt trauma].

We describe a 39-year-old woman who suffered rupture of the left auricula as a result of a non-penetrating chest wound received in a traffic accident. Rupture of the heart chambers after trauma is not infrequent, but survival is extremely rare. The patient was released from care and has suffered no subsequent complications.

Adult↗