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Biomedical subjects

P D Kaplan

Publications and source records attributed to P D Kaplan.

At least 19 recordsLinked to original sources
PubMed2005

Monodisperse double emulsions generated from a microcapillary device.

Double emulsions are highly structured fluids consisting of emulsion drops that contain smaller droplets inside. Although double emulsions are potentially of commercial value, traditional fabrication by means of two emulsification steps leads to very ill-controlled structuring. Using a microcapillary device, we fabricated double emulsions that contained a single internal droplet in a core-shell geometry. We show that the droplet size can be quantitatively predicted from the flow profiles of the fluids. The double emulsions were used to generate encapsulation structures by manipulating the properties of the fluid that makes up the shell. The high degree of control afforded by this method and the completely separate fluid streams make this a flexible and promising technique.

Journal Article↗
PubMed2001

Investigating the microenvironments of inhomogeneous soft materials with multiple particle tracking.

We develop a multiple particle tracking technique for making precise, localized measurements of the mechanical microenvironments of inhomogeneous materials. Using video microscopy, we simultaneously measure the Brownian dynamics of roughly one hundred fluorescent tracer particles embedded in a complex medium and interpret their motions in terms of local viscoelastic response. To help overcome the inherent statistical limitations due to the finite imaging volume and limited imaging times, we develop statistical techniques and analyze the distribution of particle displacements in order to make meaningful comparisons of individual particles and thus characterize the diversity and properties of the microenvironments. The ability to perform many local measurements simultaneously allows more precise measurements even in systems that evolve in time. We show several examples of inhomogeneous materials to demonstrate the flexibility of the technique and learn new details of the mechanics of the microenvironments that small particles explore. This technique extends other microrheological methods to allow simultaneous measurements of large numbers of probe particles, enabling heterogeneous samples to be studied more effectively.

Journal Article↗
PubMed2000

Two-point microrheology of inhomogeneous soft materials.

We demonstrate a novel method for measuring the microrheology of soft viscoelastic media, based on cross correlating the thermal motion of pairs of embedded tracer particles. The method does not depend on the exact nature of the coupling between the tracers and the medium, and yields accurate rheological data for highly inhomogeneous materials. We demonstrate the accuracy of this method with a guar solution, for which other microscopic methods fail due to the polymer's mesoscopic inhomogeneity. Measurements in an F-actin solution suggest conventional microrheology measurements may not reflect the true bulk behavior.

Actins↗
PubMed1997

DNA solution of the maximal clique problem.

The maximal clique problem has been solved by means of molecular biology techniques. A pool of DNA molecules corresponding to the total ensemble of six-vertex cliques was built, followed by a series of selection processes. The algorithm is highly parallel and has satisfactory fidelity. This work represents further evidence for the ability of DNA computing to solve NP-complete search problems.

Algorithms↗
PubMed1997

Parallel overlap assembly for the construction of computational DNA libraries.

Algorithms for computing with DNA currently require the construction of pools of molecules in which each distinct molecule represents a different starting point for the calculation. We have begun building such pools using the technique of parallel overlap assembly that is already used for the generation of diversity in biologically useful combinatorial search techniques such as gene shuffling. Unlike these applications, a pool in a molecular computer must be complete, containing all possible strands, and ordered, having minimal contamination from incorrectly assembled DNA. We present an experiment in which parallel overlap assembly is used to construct a computational pool and an experiment in which this pool is used to solve the NP-complete maximal-clique problem.

Algorithms↗
PubMed1997

Primary pulmonary thymoma.

Primary thymomas arising in an intrapulmonary location without an associated mediastinal component are rare entities. The origin of thymomas in this unusual location remains unknown. Knowledge of the natural history and the prognosis of these tumors is also limited because of their rarity.

Aged↗
PubMed1996

Noninvasive ventilation for postoperative support and facilitation of weaning.

Noninvasive ventilation includes continuous positive airway pressure with mask, positive pressure ventilation with mask, and negative pressure body ventilation. Noninvasive ventilation is a ventilatory support mode intermediate in both effectiveness and potential complications between oxygen administration and intubation with mechanical ventilation. The advantages, disadvantages, and experimental results of the use of noninvasive ventilation in patients who have been extubated following recovery from surgery and subsequently experience respiratory difficulties are discussed. In general, noninvasive ventilation seems to provide useful ventilatory support in about three of four patients in whom it is tried. In addition, the use of noninvasive ventilation as an aid to weaning of patients from mechanical ventilation is discussed. This use of noninvasive ventilation has not yet been extensively reported, although it appears to be potentially useful.

Acute Disease↗
PubMed1994

Noninvasive nasal mask ventilation for acute respiratory failure. Institution of a new therapeutic technology for routine use.

OBJECTIVE: We successfully implemented the delivery of noninvasive mechanical ventilation for patients with acute respiratory failure, a previously controversial use of this technique, using a simplified ventilator (BiPAP) with nasal mask. Pilot work showed this mode of support to be effective when administered by the members of a research team, and in the current study we were able to transfer this responsibility to usual care providers. SETTING: Almost 90 percent of the patients in this study were in either the 16-bed medical or 31-bed surgical intensive care units at our hospital. SUBJECTS: One hundred ten hemodynamically stable patients with acute respiratory failure being considered for intubation and mechanical ventilation participated in this study. Eighty percent were surgical patients, most of whom had hypercapnic failure. INTERVENTION: Patients were administered noninvasive ventilatory support using a ventilatory support system (BiPAP) applied with a nasal mask. This intervention was administered by a research team in the initial 31 patients (special care, phase 1). The administration was transferred to usual care personnel in the next 45 patients (transition, phase 2). Usual care personnel almost exclusively administered care in the final 34 patients (usual care, phase 3). RESULTS: Withdrawal of ventilatory support for greater than 48 h (successful outcome) was about the same during usual care (phase 3, 80 percent) as it was during special care (phase 1, 76 percent).

Acute Disease↗
PubMed1993

Tracheal perforation. A complication associated with transtracheal oxygen therapy.

A 73-year-old woman with a transtracheal oxygen catheter in place developed sudden onset of respiratory distress and subcutaneous emphysema. Bronchoscopy revealed the presence of three posterior tracheal wall perforations and a blind pouch arising from one of the perforations. Subsequent bronchoscopies revealed complete healing of the perforations. We believe that these perforations occurred during placement of the transtracheal catheter.

Aged↗
PubMed1992

Acute silicosis responding to corticosteroid therapy.

The course of acute silicosis usually is relentlessly progressive. Death results from cor pulmonale and respiratory failure, with mycobacterial infection a frequent serious complication. Attempts to treat the illness generally have been unavailing. We report an unusual case of acute silicosis in which improvement in clinical status, chest x-ray film findings and pulmonary function occurred following therapy with corticosteroids. To our knowledge, this is the first such case reported in the medical literature.

Acute Disease↗
PubMed1991

Chylothorax complicating right upper lobectomy.

Chylothorax after pleuropulmonary surgery is unusual. We have described the case of a patient in whom this complication followed a right upper lobectomy. Early recognition is important to avoid potential morbidity and mortality.

Adenocarcinoma↗
PubMed1991

Pressure support ventilation with a simplified ventilatory support system administered with a nasal mask in patients with respiratory failure.

Thirty-one consecutive patients with respiratory failure in whom treatment with intubation and mechanical ventilation was being strongly considered received alternative ventilatory support by means of a BiPAP ventilatory support system and nasal mask. Laboratory measurements and physical findings were documented before and 1 h after initiation of support. This support improved patient comfort, slowed respiratory rate, and improved oxygenation. Support lasted from 2 h to six days. Seventy-six percent (22/29) of patients recovered from this episode of respiratory failure, avoiding alternative mechanical ventilatory support. There were no complications associated with aspiration, gastric distention, or acute separation from support.

Aged↗
PubMed1977

Desquamative interstitial pneumonia-like reaction accompanying pulmonary lesions.

Six patients with specific pulmonary diseases had pulmonary tissue surgically resected for diagnostic purposes. All six cases were characterized by space-occupying lesions surrounded by a peculiar reaction of the pulmonary parenchyma indistinguishable from desquamative interstitial pneumonia. If small biopsies from these areas had been taken, a diagnosis of desquamative interstitial pneumonia would have been made, and the underlying process would have gone undetected. These cases corroborate even further the concept that desquamative interstitial pneumonia is a pattern of pulmonary reaction, rather than a well-defined disease entity. Furthermore, it seems advisable to make the dianosis of desquamative interstitial pneumonia only when other conditions have been carefully ruled out by thorough clinical and pathologic investigations.

Adult↗