Physics-based RTD current-voltage equation

An analytic expression for the current-voltage characteristics of resonant tunneling diodes is derived from basic principles. The form is ideal for insertion into circuit simulation models. It is demonstrated for a conventional InGaAs-AlAs RTD and for an InAs-AlSb-GaSb RIT diode. The expression is based on the quantum tunneling formalism and contains parameters that originate from physical quantities, but which can also be treated as empirical. Empirical fitting is straightforward and results in an excellent match to the data. Additional levels of physical realism can be incorporated in a natural way     

Do prostate specific antigen and prostate specific antigen density enhance the detection of prostate carcinoma after initial diagnosis of prostatic intraepithelial neoplasia without concurrent carcinoma?

BACKGROUND: Prostatic intraepithelial neoplasia (PIN) is considered to be a precursor of prostate carcinoma in which serum levels of prostate specific antigen (PSA) have been correlated with PIN grades. The aim of this study was to determine whether PSA and prostate specific antigen density (PSAD), obtained at the time of initial diagnosis of PIN without concurrent carcinoma, can be used as predictive factors to discriminate patients with subsequent cancer on repeat biopsy. METHODS: We studied, retrospectively, the records of 93 patients with PIN (low and high grade) without concurrent carcinoma at the time of their first needle biopsy. We assessed the relationship between initial PIN grade, PSA, and PSAD with later detection of carcinoma on repeat biopsy. Patients were divided into 3 subgroups for analysis according to their initial PSA level (0-4, 4.1-10, >10 ng/mL). RESULTS: Carcinoma detection rate on repeat biopsy was 13.3% for patients with low grade PIN and 47.7% for patients with high grade PIN (P < 0.006). High grade PIN was frequently associated with subsequent carcinoma whatever the PSA level (33.3-61.9%). Low grade PIN was associated with subsequent carcinoma in 42.8% of the cases when PSA was greater than 10 ng/mL. When PSA was between 4 and 10 ng/mL, low grade PIN carcinoma was found on repeat biopsies in only 10.7% of the cases (P = 0.05). In none of the PSA subgroups did PSAD enhance later cancer detection. CONCLUSIONS: For patients with high grade PIN, the incidence of subsequent carcinoma is high, whatever the PSA values. For these cases repeat biopsies should be recommended. Patients with low grade PIN and PSA greater than 10 ng/mL should have repeat biopsies because the incidence of subsequent carcinoma is high and comparable to high grade PIN. PSAD did not provide additional information.     

Differential histochemical peanut agglutinin stain in benign and malignant human prostate tumors: relationship with prostatic specific antigen immunostain and nuclear DNA content

The histochemical binding pattern of the peanut (Arachis hypogaea) lectin (PNA) was quantitatively described by means of computer-assisted microscope analysis in 28 benign prostatic hyperplasias (BPH), 15 prostatic intraepithelial neoplasias (PIN), and 119 prostatic adenocarcinomas. PNA exhibits nonimmune but selective binding to glycoproteins with beta-D-galactosyl(1,3)-N-acetyl-D-galactosamine residues. We also investigated whether a relationship existed between the number of histochemical-related PNA acceptors and the histochemical prostate-specific antigen (PSA) stain intensity, and between the number of PNA receptors and DNA ploidy level. The results show that neoplastic prostate tissues and high-grade intraepithelial prostatic neoplasias (PIN2_3) exhibit a significantly higher number of PNA acceptors than benign prostatic hyperplasias and low (PIN1) grade prostatic intraepithelial neoplasias. A statistically significant correlation was observed between the number of histochemically related PNA acceptors and PSA immunostain intensity. Lastly, diploid prostatic tumors, whether benign or malignant, exhibited a significantly higher number of PNA acceptors than aneuploid ones. These results suggest that PNA acceptors play an important role in the biology of prostate tumors.     

Multiple joint procedures in a single operative session on hemophilic patients

Hemophilia is a coagulation disorder wherein frequent hemarthroses result in premature joint degradation. This hemophilic osteoarthropathy is polyarticular, and despite modern coagulation possibilities, acute hemarthroses and chronic synovitis are common. Because repair of a single joint in polyarthritic conditions may not improve the patient's functional ability a policy has been adopted to create a functional limb. This therapeutic protocol succeeded in gaining the objectives of a functional limb, and it was noted that the complication rate was less than expected and that the rehabilitation period was relatively short.     

Binding of N-substituted anthracenecarboxamides to double-stranded DNA: an electronic spectral study

The electronic absorption and fluorescence spectra of two isomeric anthracenecarboxamides substituted with quaternary alkyl ammonium groups were studied as a function of solvent polarity, solvent rigidity, and state of protonation. These relatively simple environmental perturbations of the electronic spectra were employed to interpret spectral shifts caused by complexation with the bases or base pairs of DNA. The exocyclic side chains of the compounds studied have some freedom of movement when the spectroscopic probes are bound to double-stranded DNA.     

Emulating cellular automata in chemical reaction–diffusion networks

Chemical reactions and diffusion can produce a wide variety of static or transient spatial patterns in the concentrations of chemical species. Little is known, however, about what dynamical patterns of concentrations can be reliably programmed into such reaction–diffusion systems. Here we show that given simple, periodic inputs, chemical reactions and diffusion can reliably emulate the dynamics of a deterministic cellular automaton, and can therefore be programmed to produce a wide range of complex, discrete dynamics. We describe a modular reaction–diffusion program that orchestrates each of the fundamental operations of a cellular automaton: storage of cell state, communication between neighboring cells, and calculation of cells’ subsequent states. Starting from a pattern that encodes an automaton’s initial state, the concentration of a “state” species evolves in space and time according to the automaton’s specified rules. To show that the reaction–diffusion program we describe produces the target dynamics, we simulate the reaction–diffusion network for two simple one-dimensional cellular automata using coupled partial differential equations. Reaction–diffusion based cellular automata could potentially be built in vitro using networks of DNA molecules that interact via branch migration processes and could in principle perform universal computation, storing their state as a pattern of molecular concentrations, or deliver spatiotemporal instructions encoded in concentrations to direct the behavior of intelligent materials.     

Wave-packet scattering without kinematic entanglement: convergence of expectation values

The wave packet spread of a particle in a collection of different mass particles, all with Gaussian wave functions, evolves to a value that is inversely proportional to the mass of the particle. The assumptions underlying this result and its derivation are reviewed. A mathematical demonstration of the convergence of an iteration central to this assertion is presented. Finally, the question of in-principle measurement of wave packet spread is taken up.     

Risk factors for a farm vehicle public road crash

Driver, vehicle, public road, and farm enterprise characteristics were examined for their combined association with farm vehicle public road crash group membership. North Carolina farms experiencing a public road crash from 1992 to 2003 (n = 200) were compared with a non-crash control group (n = 185) for a 1:1 case:control ratio. Five characteristics were associated with increased odds of crash group membership in the combined model (likelihood ratio = 175.95; d.f. = 15; p < .001): use of non-English speaking drivers (OR = 3.71); use of non-family hired help drivers (OR = 4.25); types of non-farm vehicle public road use (OR = 1.39); farm injury history (OR = 1.33); and, use of younger farm vehicle drivers (OR = 1.02). Farms reporting older farm vehicle drivers (OR = 0.97), and low farm income (OR = 0.29) were less likely crash group members. Recommendations are discussed for incorporating findings into farm vehicle crash prevention research and interventions.