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Biomedical subjects

M W Mitchell

Publications and source records attributed to M W Mitchell.

18 recordsLinked to original sources
PubMed2004

Super-resolving phase measurements with a multiphoton entangled state.

Interference phenomena are ubiquitous in physics, often forming the basis of demanding measurements. Examples include Ramsey interferometry in atomic spectroscopy, X-ray diffraction in crystallography and optical interferometry in gravitational-wave studies. It has been known for some time that the quantum property of entanglement can be exploited to perform super-sensitive measurements, for example in optical interferometry or atomic spectroscopy. The idea has been demonstrated for an entangled state of two photons, but for larger numbers of particles it is difficult to create the necessary multiparticle entangled states. Here we demonstrate experimentally a technique for producing a maximally entangled three-photon state from initially non-entangled photons. The method can in principle be applied to generate states of arbitrary photon number, giving arbitrarily large improvement in measurement resolution. The method of state construction requires non-unitary operations, which we perform using post-selected linear-optics techniques similar to those used for linear-optics quantum computing.

Journal Article↗
PubMed2003

Diagnosis, prescription, and prognosis of a bell-state filter by quantum process tomography.

We apply the techniques of quantum process tomography to characterize errors and decoherence in a prototypical two-photon operation, a singlet-state filter. The quantum process tomography results indicate a large asymmetry in the process and also the required operation to correct for this asymmetry. We quantify residual errors and decoherence of the filtering operation after this modification.

Journal Article↗
PubMed1987

Magnetic resonance imaging in the evaluation and differentiation of uveal melanoma.

We evaluated 39 patients with intraocular disease by magnetic resonance imaging (MRI). Malignant uveal melanoma was considered the likely diagnosis in 25 patients. Seventeen patients underwent surgery, and the histopathologic diagnosis of melanoma was confirmed. The authors observed that uveal melanomas had characteristic MRI features consisting of a relatively high-signal intensity in T1-weighted images and a relatively low-signal intensity in T2-weighted images. These images reflected their inherently relative short T1 and T2 relaxation times. Choroidal lesions elevated more than 3 mm were well visualized on MRIs. MRI also proved valuable for differentiating uveal melanoma from associated subretinal effusion, choroidal hemangioma, choroidal metastasis, and hemorrhagic and serous choroidal detachments.

Adult↗
PubMedDate not supplied

Determination of fat in raw and processed milks by the Gerber method: collaborative study.

The Gerber method is used worldwide as a simple and rapid method for determining fat in raw and processed milks. However, the volume of the test portion used in the method has not been internationally agreed upon. A collaborative study was conducted to evaluate performance of the Gerber method using either a weighed test portion (11.13 g) or by a 10.77 mL test portion delivered by pipet. For each method, laboratories received 10 test samples: 5 raw and 5 pasteurized homogenized milks, 2 of which were blind duplicate pairs. Eleven and 10 laboratories participated in the evaluation of aliquot addition by weight and pipet, respectively. Mojonnier ether extraction (Method 989.05) was used as the reference method. Interlaboratory study statistics were similar between methods of test portion addition and between raw and processed materials; therefore, summary interlaboratory study statistics were pooled. The fat content of milk samples ranged from 0.96 to 5.48%. Absolute reproducibility and repeatability were not affected by fat level, and pooled statistical performance (invalid and outlier data removed) was (g fat/100 g milk) s(r) = 0.026, s(R) = 0.047, r = 0.074, and R = 0.132. Relative standard deviations increased with decreasing fat content, and were summarized by fat level: 1-2% fat milk, mean = 1.437, RSD(r) = 1.809%, RSD(R) = 3.271%; 2-6% fat milk, mean = 4.156, RSD(r) = 0.626%, RSD(R) = 1.131%. Compared with ether extraction, test results by the Gerber method were slightly lower (0.02% fat) using a weighed test portion and significantly lower (0.06% fat) using a 10.77 mL volume addition by pipet. A trend toward underestimating fat content at lower fat concentrations (1-2% fat) was observed with the weighed test portion but not when a pipet was used. The Associate Referee recommends that the Gerber method using a weighed test portion be adopted as First Action with applicability limited to whole milk.

Animals↗