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At least 163 records · Page 9Linked to original sources
PubMed2005

Physical entropy and the senses.

With reference to two specific modalities of sensation, the taste of saltiness of chloride salts, and the loudness of steady tones, it is shown that the laws of sensation (logarithmic and power laws) are expressions of the entropy per mole of the stimulus. That is, the laws of sensation are linear functions of molar entropy. In partial verification of this hypothesis, we are able to derive an approximate value for the gas constant, a fundamental physical constant, directly from psychophysical measurements. The significance of our observation lies in the linking of the phenomenon of "sensation" directly to a physical measure. It suggests that if the laws of physics are universal, the laws of sensation and perception are similarly universal. It also connects the sensation of a simple, steady physical signal with the molecular structure of the signal: the greater the number of microstates or complexions of the stimulus signal, the greater the magnitude of the sensation (saltiness or loudness). The hypothesis is currently tested on two sensory modalities.

Entropy↗
PubMed1987

Photographic detection of luminescence in Escherichia coli containing the gene for firefly luciferase.

The gene for firefly luciferase (luc) can be used as a generalized genetic probe. A method that aids in the analysis of shuttle vectors containing luc by allowing verification in Escherichia coli of a functional coding sequence is presented here. Colonies containing a functional form of luc are detected on film after luciferin is added to initiate the luminescent reaction. Two conditions, lowering the pH of the environment and maintaining aerobic conditions, were found to greatly improve the sensitivity of the assay. This technique may be useful in the development of genetic constructs that alter the natural coding sequence of luc, such as in gene fusions.

Animals↗
PubMed1979

Statistics of flexible chain configurations.

When Monte Carlo methods are employed to study the statistical dimensions of flexible polymer chains, it is necessary that the sampling be statistically unbiased. One Monte Carlo procedure is the so-called "slithering snake" technique, which has proved to be very useful. A question arises, however, as to how long it takes for a "slithering snake" to be completely regenerated to avoid biasing the samples around a particular configuration. It is demonstrated theoretically and verified by Monte Carlo studies that the number of iterations required to completely regenerate a sample polymer is a quadratic function of the chain length. This verification applies to chains in dilute solution but may not hold for bulk polymers.

Journal Article↗
PubMedDate not supplied

Mitral valve replacement in patients after aortic valve replacement.

BACKGROUND: Mitral valve replacement in patients who previously had undergone aortic valve replacement is a technical challenge. The rigid aortic prosthesis limits visualization of the anterior mitral annulus and placement of sutures. METHODS: Reoperative mitral valve replacement was performed in five patients after aortic valve replacement. Two patients underwent resternotomy to allow verification of normal aortic prosthetic valve function. Anterolateral right thoracotomy was used for reentry in the remaining three patients. Exposure of the anterior mitral annulus was accomplished by initial traction on the intact anterior leaflet, with resection of this leaflet only after placement of sutures. RESULTS: All patients survived the surgical procedure and are well 2 to 30 months after operation. In one patient it was impossible to open one cusp of the mitral prosthesis, nor was it possible to rotate the valve. The valve was reimplanted, but sutures were tied only after testing for full free cusp motion. CONCLUSIONS: When appropriate, right thoracotomy incision offers excellent exposure of the mitral valve with minimal dissection. Placement of sutures along the anterior portion of the annulus is facilitated by traction downwards on the anterior leaflet. Full range of motion of the prosthetic cusps should be verified before tying the sutures.

Aged↗
PubMed1978

Cricopharyngeal achalasia associated with Arnold-Chiari malformation in childhood.

Six patients with myelomeningocele and the Arnold-Chiari malformation developed cricopharyngeal achalasia and lower cranial nerve deficits. Diagnosis is established by cine-esophagram. Distortion of the brain stem or cranial nerves secondary to the Arnold-Chiari malformation may produce the autonomic imbalance necessary for cricopharyngeal achalasia. Treatment is supportive and includes verification of cerebral spinal fluid shunt function. Suboccipital craniectomy may reverse progressive lower cranial nerve deficits and reduce cricopharyngeus spasm. Cricopharyngeal myotomy may be considered when the cranial nerve deficits and cricopharyngeal achalasia are fixed, irreversible, and continue to cause disability.

Arnold-Chiari Malformation↗
PubMedDate not supplied

Effects of mild hypercapnia on somatosensory evoked potentials in experimental cerebral ischemia.

In a previous report, the authors demonstrated the effectiveness of mild hypercapnia in enhancing decreased perfusion flow in ischemic, non-infarcted brain tissues. However, the previous work lacked in verification of improvement of suppressed brain function. Therefore, this report was attempted to evaluate the effect of hypercapnia on somatosensory evoked potential (SEP), using the similar ischemic model as previously. The results showed that mild hypercapnia of 43 to 55 mm Hg range was beneficial not only for enhancing decreased perfusion flow but also for restoring suppressed SEP. This report seems to be the first publication which verifies a presence of correlation between local cortical blood flow (LCBF) and SEP under mild hypercapnia in mildly to moderately ischemic brain tissues.

Animals↗
PubMed2026

MCM8 promotes colorectal cancer progression by competitively inhibiting HRD1-mediated CDC42 ubiquitination and degradation.

BACKGROUND: Colorectal cancer (CRC) ranks among the top three in both incidence and mortality rates of malignant tumors worldwide. For patients with advanced colon cancer, radical surgery is challenging, and chemotherapy drugs are prone to inducing drug resistance, resulting in a five-year survival rate of only 13.1%. Therefore, in-depth analysis of the occurrence, development, and drug resistance mechanisms of colon cancer is of great clinical significance for optimizing treatment strategies and improving patient prognosis. As one of the homologous recombination repair proteins, minichromosomal maintenance protein 8 (MCM8) not only participates in DNA replication initiation, homologous recombination repair, and genome stability maintenance in normal cells, but also has been reported to be abnormally highly expressed in multiple tumors (e.g. glioblastoma, cholangiocarcinoma, bladder cancer) to promote malignant progression. METHODS: This study focused on the expression and function of MCM8 in colon cancer. The expression level of MCM8 in colon cancer tissues and cells was detected, and its correlation with patients’ clinicopathological features and prognosis was analyzed. Combined with cell function experiments, protein-protein interaction verification assays, and in vivo tumorigenesis experiments, the effects of MCM8 on the biological behaviors of colon cancer cells and the underlying molecular mechanisms were explored. Meanwhile, rescue experiments were conducted to identify the key downstream molecules and pathways mediated by MCM8. Additionally, the relationship between MCM8 and chemoresistance of colon cancer cells was investigated. RESULTS: Our study indicated that MCM8 promotes the transition of the cell cycle from the G1 phase to the S phase in CRC cell lines(SW620, HCT116, CX-1). Moreover, our study showed that MCM8 interacted with Cdc42(Cell Division Cycle 42) and promoted its protein stability by competitively inhibiting the ubiquitination modification of Cdc42‘s E3 ubiquitin ligase HRD1(Hydroxymethylglutaryl Reductase Degradation Protein 1). The rescue experiment showed that MCM8 promoted the proliferation, cell cycle progression, invasion, tumor-forming ability in vivo and resistance to 5-FU of CRC cell lines (SW620FR, HCT15FR) through Cdc42, while inhibiting cell apoptosis. CONCLUSIONS: MCM8 is abnormally highly expressed in CRC and stabilizes Cdc42 protein by competitively inhibiting HRD1, thereby promoting the occurrence and development of CRC and the formation of 5-FU resistance.

Humans↗
PubMed1987

Reading fields of magnifying loupes.

For the purpose of understanding the influence of the use of magnifying loupes on the reading process, the reading field is a relevant concept. Three possible reading fields are distinguished: the monocular reading field, the binocular reading field, and the composite reading field. Theoretical expressions for the widths of reading fields are derived as a function of the physical parameters of the loupe and the geometry of the reading situation. Variation of reading-field width as a function of magnification is illustrated. For verification, experimentally determined reading-field widths were compared with the theoretical ones. There were small systematic deviations, probably caused by achromatic aberrations. In order to learn about the strategies that subjects use when reading with the aid of a loupe, loupe displacement was measured while subjects read text under conditions that provided a variety of reading-field widths. It was found that individual subjects use different strategies (i.e., they use different reading-field widths).

Fovea Centralis↗
PubMed1989

Are words represented by nodes?

Semantic priming in a lexical decision task was investigated with concurrent pretarget and posttarget primes. The posttarget prime also served as a pattern mask of the lexical decision target. Forward priming is defined as the presence of a semantically related pretarget prime and an unrelated posttarget prime. Backward priming is defined as the presence of a semantically related posttarget prime and an unrelated pretarget prime. Forward and backward priming were compared both when the nonword foils were "legal" and when they were "illegal" with respect to English orthography. Predictions were derived for two general approaches to word recognition: spreading-activation and expectancy-set theories. Both approaches assume that word representations occupy distinct, nonoverlapping locations in memory. Backward-prime facilitation was equivalent to forward-prime facilitation when nonword foils were illegal; however, backward-prime facilitation was not significant when nonword foils were legal. These results challenge both approaches. The proposed solution uses semantic-space (distributed) representations that are functionally unitized by a resonant matching (verification) process.

Adult↗
PubMedDate not supplied

[Thyroid carcinoma in childhood].

A retrospective analysis of the thyroid gland carcinoma in children, cured at the Institute of Oncology, was more frequent in girls (76%) than in boys. The changes were analysed according to TNM classification using the protocol for diagnostic and treatment procedures. The approach of the protocol was the same for children and adult population. In children the primary process ecpanded very fast in regional lymph nodes. Surgery of different size with or without the functionally neck dissection, proved the pathohistological verification. After the surgery, in 10 of 29 children, 131-I was applied. Spreading of the disease in lungs was observed in four of 29 children. The parameters of the successful therapy of the thyroid gland carcinoma in childhood were the general status, local status, the concentration of thyroglobulin value (Tg), and the serum titres of antithyroglobulin antibodies.

Adolescent↗
PubMed2005

[Research on metrological verification and the development of the verification equipment for digital electrocardiographs].

In order to guarantee that digital electrocardiographs with an adequate accuracy and reliabity are available for measurements in clinical practice, it is very important to determine the metrological characteristics, methods and to develop the equipments for verification. This paper elaborates the basic functions, specification, schematic drawing and key techniques of calibration equipments as well as test items for digital electrocardiographs.

Electrocardiography↗
PubMed1991

[Comparison of the results of early and delayed rehabilitation in patients with surgery for disco-radicular problems in the lumbar spine].

When painful remission and functional spine restitution with patients with verificated lumbal dischernia haven't been achieved by an adequate conservative treatment, an operation is to be performed. The aim of post-operative way of rehabilitation is to give the spine back the most possible nimbleness, to remove remained pains, to make the existing motoric deficit better if possible and to make the patient fit socially as well as professionally. Post-operation rehabilitation results of patients treated by inter-laminectomy of L4/L5 or L5/S1 segments were analysed retrospectively in this study. Compared groups differed in rehabilitation programme beginning time, so with group A it began 10-20 days and with group B 35 or more days after the operation. Clinical parametres observed were lumbal spine flexibility, paravertebral muscularity tension, motile painfulness, Lasegue sign presence and neurotic outbursts in motorical and sensual sphere. The achieved results show that late beginning of rehabilitation has no advantage in definite medical treatment results. Therefore the patients should be sent to rehabilitation centres after the catgut being taken out.

Adult↗
PubMed1990

Evaluation of an in-situ output probe-microphone method for hearing aid fitting verification.

Several hearing aid prescription procedures specify frequency gain functions in terms of the desired levels of amplified speech. The most direct method for verifying hearing aid fittings based on these procedures requires a measurement of amplified speech in the ear canal. This paper describes the evaluation of a probe microphone measurement procedure designed to measure amplified speech to verify hearing aid fittings using the MSUv3 prescription procedure. With minor modifications, the same protocol could be used with other prescriptive procedures. Hearing aids were fitted to a group of subjects with sensorineural hearing impairment. Data derived from the fittings were analyzed to assess several issues relating to the procedure itself and to prescriptive fittings in general. The main results were: (1) with over the ear hearing aids, most prescriptions can be matched with an RMS error of 5 dB or less through the frequency range from 500 to 2500 Hz; (2) even though actual fittings usually do not perfectly correspond with their prescriptions, differences among frequency gain prescriptions are preserved in hearing aid fittings if the RMS error of the fitting is 5 dB or less; (3) if sound field stimuli presented to the hearing aid are precisely controlled, an in situ output verification method produces valid results; (4) when hearing aids are fitted with gain similar to that prescribed by the MSUv3 procedure, the maximum comfortable speech input level is typically about 72 dB; (5) the SSPL90 prescription generated by the MSUv3 procedure overestimates desired SSPL90 by 7 dB on average.

Audiometry↗
PubMed2006

Demonstration of lysosomal localization for the mammalian ependymin-related protein using classical approaches combined with a novel density shift method.

Most newly synthesized soluble lysosomal proteins are delivered to the lysosome via the mannose 6-phosphate (Man-6-P)-targeting pathway. The presence of the Man-6-P post-translational modification allows these proteins to be affinity-purified on immobilized Man-6-P receptors. This approach has formed the basis for a number of proteomic studies that identified multiple as yet uncharacterized Man-6-P glycoproteins that may represent new lysosomal proteins. Although the presence of Man-6-P is suggestive of lysosomal function, the subcellular localization of such candidates requires experimental verification. Here, we have investigated one such candidate, ependymin-related protein (EPDR). EPDR is a protein of unknown function with some sequence similarity to ependymin, a fish protein thought to play a role in memory consolidation and learning. Using classical subcellular fractionation on rat brain, EPDR co-distributes with lysosomal proteins, but there is significant overlap between lysosomal and mitochondrial markers. For more definitive localization, we have developed a novel approach based upon a selective buoyant density shift of the brain lysosomes in a mutant mouse lacking NPC2, a lysosomal protein involved in lipid transport. EPDR, in parallel with lysosomal markers, shows this density shift in gradient centrifugation experiments comparing mutant and wild type mice. This approach, combined with morphological analyses, demonstrates that EPDR resides in the lysosome. In addition, the lipidosis-induced density shift approach represents a valuable tool for identification and validation of both luminal and membrane lysosomal proteins that should be applicable to high throughput proteomic studies.

Animals↗
PubMed2000

New computer procedure for routine EPR-dosimetry on tooth enamel: description and verification.

A software code was developed for fitting the EPR tooth enamel spectrum using linear combinations of Gaussian functions. The software is fastening EPR dose reconstruction for routine applications. The verification of the software was done comparing with the selective saturation method as an independent procedure of signal evaluation. Both methods were applied for the dose reconstruction of 13 teeth mostly from the Techa riverside. The evaluated doses by the two methods demonstrate an excellent agreement.

Dental Enamel↗
PubMed2002

Density functional calculations for modeling the oxidized states of the active site of nickel-iron hydrogenases. 1. Verification of the method with paramagnetic Ni and Co complexes.

ZORA relativistic DFT calculations are presented which aim to reproduce geometric structures and EPR properties of [Ni(mnt)(2)](-) (H(2)mnt = maleonitrildithiol), two other paramagnetic low-spin Ni(III) complexes, and an asymmetric paramagnetic Co(II) complex. The study tests the accuracy of the computational method as a prior step to the modeling of the geometric and electronic structure of the active site of NiFe hydrogenases in its EPR-active oxidized states Ni-A and Ni-B. Systematic deviations from experiment are found for the calculated g-values; relative differences among them are, however, well reproduced. Because no significant improvements have been achieved by using larger basis sets or more sophisticated functionals, g-values may be calculated rather rapidly at the VWN level. This is most important for the modeling of the active site of NiFe hydrogenases because its complexity does not permit calculations at high levels of theory. For [Ni(mnt)(2)](-), excellent agreement between calculated and experimental results is obtained for the (14)N quadrupole coupling, whereas the calculated hyperfine couplings are not always in good agreement with experimental data.

Anisotropy↗
PubMed2001

Verification of a distortion in the microstructure of GaN detected by EXAFS using ab initio density functional theory calculations.

X-ray absorption fine structure (XAFS) measurements on a series of epitaxially grown GaN samples have shown a distortion in the microstructure of GaN. More specifically the central N atom is 4-fold coordinated but the four Ga atoms are not equidistant. It has been shown that 2.9 to 3.5 of them (depending on the growth conditions) are found in the expected from XRD distance of 1.94 A and the remaining are at a distance longer by approximately 15%. Second derivative calculation of the conformation energy using the Density Functional Theory (DFT) is used to investigate if the symmetric GaN cluster as given by XRD is the most energetically favorable configuration and if not which distorted structure corresponds to the most energetically favorable one. A very good agreement between DFT results and experimental XAFS spectra has been found. Generalization this technique to other dislocated clusters is also discussed.

Journal Article↗