Consequences of imperfect mixing the Gray-Scott model.

We study an autocatalytic reaction-diffusion scheme, the Gray-Scott model, when the mixing processes do not homogenize the reactants. Starting from the master equation, we derive the resulting coupled, nonlinear, stochastic partial differential equations that rigorously include the spatiotemporal fluctuations resulting from the interplay between the reaction and mixing processes. The fields are complex and depend on correlated complex noise terms. We implement a method to solve for these complex fields numerically and extract accurate information about the system evolution and stationary states under different mixing regimes. Through this example, we show how the reaction-induced fluctuations interact with the temporal nonlinearities, leading to results that differ significantly from the mean-field (perfectly mixed) approach. This procedure can be applied to an arbitrary nonlinear reaction diffusion scheme.

Reaction-diffusion model for pattern formation in E. coli swarming colonies with slime.

A new experimental colonial pattern and pattern transition observed in E. coli MG1655 swarming cells grown on semisolid agar are described. We present a reaction-diffusion model that, taking into account the slime generated by these cells and its influence on the bacterial differentiation and motion, reproduces the pattern and successfully predicts the observed changes when the colonial collective motility is limited. In spite of having small nonhyperflagellated swarming cells, under these experimental conditions E. coli MG1655 can very rapidly colonize a surface, with a low branching rate, thanks to a strong fluid production and a locally incremented density of motile, lubricating cells.

Erectile function after anterior urethroplasty.

PURPOSE: We ascertained the impact of anterior urethroplasty on male sexual function. MATERIALS AND METHODS: A validated questionnaire was mailed to 200 men who underwent anterior urethroplasty to evaluate postoperative sexual function. Questions addressed the change in erect penile length and angle, patient satisfaction with erection, preoperative and postoperative coital frequency, and change in erection noted by the sexual partner. Results were stratified by the urethral reconstruction method, namely anastomosis, buccal mucosal graft, penile flap and all others, and compared with those in a similar group of men who underwent circumcision only. RESULTS: Of the 200 men who underwent urethroplasty 152 who were 17 to 83 years old (mean age 45.7) completed the questionnaire. Average followup was 36 months (range 3 to 149). Overall there was a similar incidence of sexual problems after urethroplasty and circumcision. Penile skin flap urethroplasty was associated with a slightly higher incidence of impaired sexual function than other procedures (p >0.05). Men with a longer stricture were most likely to report major changes in erectile function and penile length (p <0.05) but improvement was evident with time in 61.8%. CONCLUSIONS: Overall anterior urethral reconstruction appears no more likely to cause long-term postoperative sexual dysfunction than circumcision. Men with a long stricture may be at increased risk for transient erectile changes.

Heat kernel regularization of the effective action for stochastic reaction-diffusion equations.

The presence of fluctuations and nonlinear interactions can lead to scale dependence in the parameters appearing in stochastic differential equations. Stochastic dynamics can be formulated in terms of functional integrals. In this paper we apply the heat kernel method to study the short distance renormalizability of a stochastic (polynomial) reaction-diffusion equation with real additive noise. We calculate the one-loop effective action and its ultraviolet scale dependent divergences. We show that for white noise a polynomial reaction-diffusion equation is one-loop finite in d=0 and d=1, and is one-loop renormalizable in d=2 and d=3 space dimensions. We obtain the one-loop renormalization group equations and find they run with scale only in d=2.

Relationship of prostate-specific antigen and prostate volume in patients with biopsy proven benign prostatic hyperplasia.

BACKGROUND: Emerging data suggest a direct correlation between prostate-specific antigen (PSA) and prostate volume in patients with lower urinary tract symptoms (LUTS) and clinical evidence of benign prostatic hyperplasia (BPH). We attempt to confirm that a similar correlation exists between PSA and prostate volume in patients with biopsy-proven BPH. METHODS: Over a 5 year period, 2,270 patients were confirmed to have BPH as the only histological diagnosis after evaluation with serum PSA, trans-rectal ultrasound (TRUS) biopsy, and prostate volume measurement. PSA and prostate volume were statistically analyzed by age-stratified cohorts, including multiple regression analysis and assessment of correlation using the Pearson correlation coefficient (r). RESULTS: Mean PSA and prostate volume increased with each advancing cohort of age, and the correlation of PSA and prostate volume was determined to be statistically significant (P < 0.001) in each cohort with a correlation coefficient ranging from 0.33 to 0.41. CONCLUSIONS: We confirm that the relationship between PSA and prostate volume in a large series of patients with biopsy-proven BPH provides a comparable correlation to data for patients with LUTS and clinical BPH. As such, PSA represents a valuable approximation of prostate volume, and may prove to be clinically useful in the management of patients with BPH.

Renormalization group analysis of a quivering string model of posture control.

Scaling concepts and renormalization group methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise, intended to model the corrections of the physiological control system. We find that adding a weak quadratic nonlinearity to the posture control model opens up a rich and complicated phase space (representing the dynamics) with various nontrivial fixed points and basins of attraction. The transition from diffusive to saturated regimes of the linear model is understood as a crossover phenomenon, and the robustness of the linear model with respect to weak nonlinearities is confirmed. Correlations in posture fluctuations are obtained in both time and space domains. There is an attractive fixed point identified with falling. The scaling of the correlations in the front-back displacement, which can be measured in the laboratory, is predicted for both large-separation (along the string) and long-time regimes of posture control.

The expression pattern of Epstein-Barr virus latent genes in vivo is dependent upon the differentiation stage of the infected B cell.

Epstein-Barr virus-infected B cells in vivo demonstrate three distinct patterns of latent gene expression, depending on the differentiation stage of the cell. Tonsillar naive B cells express the EBNA2-dependent lymphoblastoid phenotype, characteristic of direct infection. Germinal center centroblasts and centrocytes as well as tonsillar memory B cells express a more restricted pattern of latent genes (EBNA1(Q-K)+, LMP1+, LMP2+, EBNA2-) that has only been seen previously in EBV-positive tumors. Peripheral memory cells express an even more restricted pattern where no latent genes are expressed, with the possible exception of LMP2. These results are consistent with a model where EBV uses the normal biology of B lymphocytes to gain access to and persist within the long-lived memory B cell compartment.

Interstitial fibrosis of unilateral ureteral obstruction is exacerbated in kidneys of mice lacking the gene for inducible nitric oxide synthase.

Unilateral ureteral obstruction (UUO) is characterized by decreases in renal function and increases in interstitial fibrosis. Previous studies have indicated that pharmacologic manipulations that increase nitric oxide (NO) are beneficial to the obstructed kidneys. NO is produced from arginine by nitric oxide synthase (NOS), an enzyme that exists in both constitutive and inducible (iNOS) forms. To determine the role of the inducible form of NOS in UUO, we used mice with a targeted deletion of iNOS (iNOS -/- mice) and compared them with wild-type (WT) mice. Kidneys were obstructed for 2 weeks in both WT and iNOS -/- mice, and were then removed and bisected. Half of the kidney was embedded in paraffin and tissue sections were examined for interstitial volume or the presence of macrophages. The remainder was flash-frozen and samples were used to measure tissue collagen (hydroxyproline) or transforming growth factor-beta (TGF-beta). This study demonstrates that both cortex and medulla of obstructed kidneys of iNOS -/- mice exhibit significantly increased interstitial volume and interstitial macrophages as compared with their WT counterparts. Furthermore tissue collagen was increased to 9.2+/-1.3 microg/mg tissue in WT obstructed kidneys, whereas in iNOS -/- kidneys, collagen was increased to 13.2+/-0.8 microg/mg tissue. The profibrotic cytokine TGF-beta was also significantly increased in obstructed kidneys of iNOS -/- mice, as compared with WT mice. No differences were noted between the unobstructed kidneys of iNOS -/- mice compared with WT mice in any of the parameters examined. These results demonstrate that targeted deletion of the iNOS results in exacerbation of fibrotic events in the obstructed kidney. These results confirm previous pharmacologic studies, and suggest that NO produced via the inducible NOS normally serves a protective function in UUO.

Effective action for stochastic partial differential equations.

Stochastic partial differential equations (SPDEs) are the basic tool for modeling systems where noise is important. SPDEs are used for models of turbulence, pattern formation, and the structural development of the universe itself. It is reasonably well known that certain SPDEs can be manipulated to be equivalent to (nonquantum) field theories that nevertheless exhibit deep and important relationships with quantum field theory. In this paper we systematically extend these ideas: We set up a functional integral formalism and demonstrate how to extract all the one-loop physics for an arbitrary SPDE subject to arbitrary Gaussian noise. It is extremely important to realize that Gaussian noise does not imply that the field variables undergo Gaussian fluctuations, and that these nonquantum field theories are fully interacting. The limitation to one loop is not as serious as might be supposed: Experience with quantum field theories (QFTs) has taught us that one-loop physics is often quite adequate to give a good description of the salient issues. The limitation to one loop does, however, offer marked technical advantages: Because at one loop almost any field theory can be rendered finite using zeta function technology, we can sidestep the complications inherent in the Martin-Siggia-Rose formalism (the SPDE analog of the Becchi-Rouet-Stora-Tyutin formalism used in QFT) and instead focus attention on a minimalist approach that uses only the physical fields (this "direct approach" is the SPDE analog of canonical quantization using physical fields). After setting up the general formalism for the characteristic functional (partition function), we show how to define the effective action to all loops, and then focus on the one-loop effective action and its specialization to constant fields: the effective potential. The physical interpretation of the effective action and effective potential for SPDEs is addressed and we show that key features carry over from QFT to the case of SPDEs. An important result is that the amplitude of the two-point function governing the noise acts as the loop-counting parameter and is the analog of Planck's constant in this SPDE context. We derive a general expression for the one-loop effective potential of an arbitrary SPDE subject to translation-invariant Gaussian noise, and compare this with the one-loop potential for QFT.

Thyrotoxic periodic paralysis in a black man.

We report a case of thyrotoxic hypokalemic periodic paralysis occurring in a black man. This previously healthy 41-year-old man had a 3-year history of recurrent paroxysmal episodes of paresis in the upper and lower extremities proximally, often occurring after heavy exercise. The patient had no history of hyperthyroidism, nor family history of periodic paralysis. This case reveals a particularly rare characteristic of this disorder in which periodic paralysis is the presenting symptom of hyperthyroidism. This condition has been reported most commonly among Asians and is extremely rare in black men, only five cases having been described during the past 30 years.

Incidental prostatic adenocarcinoma in patients undergoing radical cystoprostatectomy for bladder cancer.

To determine if patients with bladder cancer have a higher incidence of unsuspected prostate cancer, 40 cases were studied. All except one case had no evidence of prostate cancer on preoperative clinical assessment. Detailed pathological evaluation of cystoprostatectomy specimens with sections at 2- to 3-mm intervals was done. Adenocarcinoma of the prostate was identified in 18 of 40 patients (45%). Multifocal prostatic intraepithelial neoplasia (PIN) was present in 19 cases (47.5%); 4 (10%) without an associated prostate cancer and 15 (37.5%) in conjunction with adenocarcinoma of the prostate. Twelve cases of unsuspected prostate cancer were stage pT1a, 4 were pT1b, and 2 were pT3. No patients exhibited nodal or distance metastases by the prostate cancer. At a mean follow-up of 15.2 months (range 3-34 months), 37 of the 40 patients are alive. Among prostate cancer patients, no clinical or biochemical evidence of disease recurrence or prostate cancer related mortality has been observed. Our findings support the previously reported high incidence rate of prostate cancer in patients undergoing cystoprostatectomy for bladder cancer. This, though, may not be higher than the observed incidence in an age-matched general population. We recommend DRE and PSA as part of the bladder cancer workup in males, and complete removal of the prostate at cystoprostatectomy to prevent the dilemma of residual prostate cancer.