Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation

High-power Z pinches on Sandia National Laboratories' Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF2 were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution in each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s-->2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1sigma to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF2 samples is understood within the accuracy of the spectroscopic method.

Management of spotted wilt vectored by Frankliniella fusca (Thysanoptera: Thripidae) in Virginia market-type peanut

Field tests were conducted during 2001 and 2002 in northeastern North Carolina to evaluate the impact of cultural practices and in-furrow insecticides on the incidence of Tomato spotted wilt virus (genus Tospovirus, family Bunyaviridae, TSWV), which is transmitted to peanut, Arachis hypogaea L., primarily by tobacco thrips, Frankliniella fusca Hinds (Thysanoptera: Thripidae). Treatments included in row plant populations of 7, 13, and 17 plants per meter; the virginia market-type 'NC V-11' and 'Perry'; planting dates of early and late May; and phorate and aldicarb insecticide applied in-furrow. The incidence of plants expressing visual symptoms of spotted wilt was recorded from mid-June through mid-September. Treatment factors that reduced the incidence of symptoms of plants expressing spotted wilt symptoms included establishing higher plant densities, delaying planting from early May until late May, and applying the in-furrow insecticide phorate. Peanut cultivar did not have a consistent, significant effect on the incidence of symptomatic plants in this experiment.

ROC study of the effect of stereoscopic imaging on assessment of breast lesions

An observer performance study was conducted to evaluate the usefulness of assessing breast lesion characteristics with stereomammography. Stereoscopic image pairs of 158 breast biopsy tissue specimens were acquired with a GE Senographe 2000D full field digital mammography system using a 1.8x magnification geometry. A phantom-shift method equivalent to a stereo shift angle of +/- 3 degrees relative to a central axis perpendicular to the detector was used. For each specimen, two pairs of stereo images were taken at approximately orthogonal orientations. The specimens contained either a mass, microcalcifications, both, or normal tissue. Based on pathological analysis, 39.9% of the specimens were found to contain malignancy. The digital specimen radiographs were displayed on a high resolution MegaScan CRT monitor driven by a DOME stereo display board using in-house developed software. Five MQSA radiologists participated as observers. Each observer read the 316 specimen stereo image pairs in a randomized order. For each case, the observer first read the monoscopic image and entered his/her confidence ratings on the presence of microcalcifications and/or masses, margin status, BI-RADS assessment, and the likelihood of malignancy. The corresponding stereoscopic images were then displayed on the same monitor and were viewed through stereoscopic LCD glasses. The observer was free to change the ratings in every category after stereoscopic reading. The ratings of the observers were analyzed by ROC methodology. For the 5 MQSA radiologists, the average Az value for estimation of the likelihood of malignancy of the lesions improved from 0.70 for monoscopic reading to 0.72 (p=0.04) after stereoscopic reading, and the average Az value for the presence of microcalcifications improved from 0.95 to 0.96 (p=0.02). The Az value for the presence of masses improved from 0.80 to 0.82 after stereoscopic reading, but the difference fell short of statistical significance (p=0.08). The visual assessment of margin clearance was found to have very low correlation with microscopic analysis with or without stereoscopic reading. This study demonstrates the potential of using stereomammography to improve the detection and characterization of mammographic lesions.

An observer study comparing spot imaging regions selected by radiologists and a computer for an automated stereo spot mammography technique

We are developing an automated stereo spot mammography technique for improved imaging of suspicious dense regions within digital mammograms. The technique entails the acquisition of a full-field digital mammogram, automated detection of a suspicious dense region within that mammogram by a computer aided detection (CAD) program, and acquisition of a stereo pair of images with automated collimation to the suspicious region. The latter stereo spot image is obtained within seconds of the original full-field mammogram, without releasing the compression paddle. The spot image is viewed on a stereo video display. A critical element of this technique is the automated detection of suspicious regions for spot imaging. We performed an observer study to compare the suspicious regions selected by radiologists with those selected by a CAD program developed at the University of Michigan. True regions of interest (TROIs) were separately determined by one of the radiologists who reviewed the original mammograms, biopsy images, and histology results. We compared the radiologist and computer-selected regions of interest (ROIs) to the TROIs. Both the radiologists and the computer were allowed to select up to 3 regions in each of 200 images (mixture of 100 CC and 100 MLO views). We computed overlap indices (the overlap index is defined as the ratio of the area of intersection to the area of interest) to quantify the agreement between the selected regions in each image. The averages of the largest overlap indices per image for the 5 radiologist-to-computer comparisons were directly related to the average number of regions per image traced by the radiologists (about 50% for 1 region/image, 84% for 2 regions/image and 96% for 3 regions/image). The average of the overlap indices with all of the TROIs was 73% for CAD and 76.8% +/- 10.0% for the radiologists. This study indicates that the CAD determined ROIs could potentially be useful for a screening technique that includes stereo spot mammography imaging.

Estimating the effects of informal radiology resident teaching on radiologist productivity: what is the cost of teaching?

RATIONALE AND OBJECTIVES

One mission of an academic radiology department is to teach. The greatest teaching effort is directed at radiology residents. As clinical work demands increase, informal, non-revenue-generating, teaching may suffer. We sought to determine the economic consequences of teaching.

MATERIALS AND METHODS

With the use of a picture archiving and communications system, 6 radiology faculty members independently interpreted and dictated digitally acquired bone and chest radiographs for 1 hour alone and again 10-12 weeks later with a first-year resident. During the second session, the quality of teaching was graded by independent observers. The number of cases, relative value units (RVUs), and reimbursement for each session were calculated.

RESULTS

The difference in number of cases dictated working alone (mean, 44.7) and with a first-year resident (mean, 23.5) was significant (P = 0.007). The difference between RVUs generated by faculty alone (mean, 9.0) and with a resident (mean, 4.5) also was significant (P = 0.006), and the difference in dollars billed when working alone (mean, $1558.45) and with a resident (mean, $777.65) was significant (P = 0.007). As teaching quality increased, the number of cases interpreted, dollars billed, and RVUs trended lower.

CONCLUSION

Informal resident teaching significantly reduces clinical throughput, reducing examination volume, RVUs, and dollars billed by approximately half.

Small (<2.0-cm) Breast Cancers: Mammographic and US Findings at US-guided Cryoablation—Initial Experience

PURPOSE

To determine the mammographic and ultrasonographic (US) findings at cryoablation of small solitary invasive breast cancers and compare them with presence of residual malignancy after treatment.

MATERIALS AND METHODS

Institutional review board approval and informed patient consent were obtained. Nine patients with small solitary invasive breast cancers diagnosed at core biopsy were treated with US-guided cryoablation and a 2.7-mm cryoprobe. Mean cancer size was 12 mm (range, 8-18 mm); four were palpable. Tabletop argon gas-based cryoablation system with a double-freeze-thaw protocol was used to treat cancers in outpatient setting. Tumor sites were excised at lumpectomy 2-3 weeks after cryoablation. Findings at mammography and US before, during, and after cryoablation were assessed to categorize densities and masses on mammograms and masses on US images with Breast Imaging Reporting and Data System (BI-RADS); maximum cancer size was measured. Imaging findings and clinical breast examination data were compared with histologic findings from lumpectomy specimens to determine presence of intraductal or invasive cancer.

RESULTS

With US guidance, ice balls (maximal mean size, 4.4 cm) were formed around cancers. Before excision, eight patients underwent mammography; all had new focal densities (maximum size, 2.5-5.0 cm) at cancer sites. Six patients underwent preexcisional US; 100% of them had new hyperechogenicity in tissue surrounding cancer site. Seven (78%) of nine patients had no residual cancer; specimens contained fat necrosis. One patient had a small focus of invasive cancer; one had extensive multifocal ductal carcinoma in situ. Patients with BI-RADS category 1 or 2 densities on mammograms or nonpalpable tumors had no residual malignancy. No residual invasive cancer occurred in tumors 17 mm or smaller or in cancers without spiculated margins at US.

CONCLUSION

After cryoablation, there was increased echogenicity at US and increased density at mammography; these findings were observed in areas that approximated location and size of the ice ball. Tumor size, mammographic density, and US characteristics may be indicators of likelihood of complete cryoablation.

Using sleep to evaluate comparative serotonergic effects of paroxetine and citalopram

BACKGROUND

SSRIs suppress rapid eye movement (REM) sleep, probably by increasing serotonin in the brainstem, and also increase sleep fragmentation. Although in the UK, paroxetine (PAR) and citalopram (CIT) have recommended doses of 20 mg/day for the treatment of depression, the recommended dose of CIT in USA is higher (40 mg). If similar doses of PAR and CIT have similar effects on central serotonin then they should have similar effects on sleep measures in volunteers.

METHOD

This was a randomised, double blind placebo controlled crossover study in 12 healthy volunteers. Subjects took PAR 20 mg mane, CIT 20 mg mane or placebo mane for 3 days and sleep was recorded overnight at home on the third night. Standard measures of sleep were derived.

RESULTS

REM sleep was significantly suppressed and sleep fragmentation increased by both drugs. Measures of REM sleep and sleep continuity previously found to be altered by SSRIs were considered together and compared with placebo as a 'serotonin response'; this was significantly greater in the PAR group.

CONCLUSIONS

Sleep effects typical of SSRIs were greater with PAR 20 mg/day than CIT 20 mg/day, suggesting greater effects on 5HT uptake blockade.

Effects of magnification and zooming on depth perception in digital stereomammography: an observer performance study

We are evaluating the application of stereoscopic imaging to digital mammography. In the current study, we investigated the effects of magnification and zooming on depth perception. A modular phantom was designed which contained six layers of 1-mm-thick Lexan plates, each spaced 1 mm apart. Eight to nine small, thin nylon fibrils were pasted on each plate in horizontal or vertical orientations such that they formed 25 crossing fibril pairs in a projected image. The depth separation between each fibril pair ranged from 2 to 10 mm. A change in the order of the Lexan plates changed the depth separation of the two fibrils in a pair. Stereoscopic image pairs of the phantom were acquired with a GE full-field digital mammography system. Three different phantom configurations were imaged. All images were obtained using a Rh target/Rh filter spectrum at 30 kVp tube potential and a +/- 3 stereo shift angle. Images were acquired in both contact and 1.8X magnification geometry and an exposure range of 4 to 63 mAs was employed. The images were displayed on a Barco monitor driven by a Metheus stereo graphics board and viewed with LCD stereo glasses. Five observers participated in the study. Each observer visually judged whether the vertical fibril was in front of or behind the horizontal fibril in each fibril pair. It was found that the accuracy of depth discrimination increased with increasing fibril depth separation and x-ray exposure. The accuracy was not improved by electronic display zooming of the contact stereo images by 2X. Under conditions of high noise (low mAs) and small depth separation between the fibrils, the observers' depth discrimination ability was significantly better in stereo images acquired with geometric magnification than in images acquired with a contact technique and displayed with or without zooming. Under our experimental conditions, a 2 mm depth discrimination was achieved with over 60% accuracy on contact images with and without zooming, and with over 90% accuracy on magnification images. This study indicates that stereoscopic imaging, especially with magnification, may be useful for visualizing the spatial distribution of microcalcifications in a cluster and for differentiating overlapping tissues from masses on mammograms.

Charge-state distribution and Doppler effect in an expanding photoionized plasma

The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter xi=20-25 erg cm s(-1) under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.

X-ray emission from z pinches at 10 7 A: current scaling, gap closure, and shot-to-shot fluctuations

We have measured the x-ray power and energy radiated by a tungsten-wire-array z pinch as a function of the peak pinch current and the width of the anode-cathode gap at the base of the pinch. The measurements were performed at 13- and 19-MA currents and 1-, 2-, 3-, and 4-mm gaps. The wire material, number of wires, wire-array diameter, wire-array length, wire-array-electrode design, normalized-pinch-current time history, implosion time, and diagnostic package were held constant for the experiments. To keep the implosion time constant, the mass of the array was increased as I2 (i.e., the diameter of each wire was increased as I), where I is the peak pinch current. At 19 MA, the mass of the 300-wire 20-mm-diam 10-mm-length array was 5.9 mg. For the configuration studied, we find that to eliminate the effects of gap closure on the radiated energy, the width of the gap must be increased approximately as I. For shots unaffected by gap closure, we find that the peak radiated x-ray power P(r) proportional to I1.24+/-0.18, the total radiated x-ray energy E(r) proportional to I1.73+/-0.18, the x-ray-power rise time tau(r) proportional to I0.39+/-0.34, and the x-ray-power pulse width tau(w) proportional to demonstrate that the internal energy and radiative opacity of the pinch are not responsible for the observed subquadratic power scaling. Heuristic wire-ablation arguments suggest that quadratic power scaling will be achieved if the implosion time tau(i) is scaled as I(-1/3). The measured 1sigma shot-to-shot fluctuations in P(r), E(r), tau(r), tau(w), and tau(i) are approximately 12%, 9%, 26%, 9%, and 2%, respectively, assuming that the fluctuations are independent of I. These variations are for one-half of the pinch. If the half observed radiates in a manner that is statistically independent of the other half, the variations are a factor of 2(1/2) less for the entire pinch. We calculate the effect that shot-to-shot fluctuations of a single pinch would have on the shot-success probability of the double-pinch inertial-confinement-fusion driver proposed by Hammer et al. [Phys. Plasmas 6, 2129 (1999)]. We find that on a given shot, the probability that two independent pinches would radiate the same peak power to within a factor of 1+/-alpha (where 0< or =alpha<<1) is equal to erf(alpha/2sigma), where sigma is the 1sigma fractional variation of the peak power radiated by a single pinch. Assuming alpha must be < or =7% to achieve adequate odd-Legendre-mode radiation symmetry for thermonuclear-fusion experiments, sigma must be <3% for the shot-success probability to be > or =90%. The observed (12/2(1/2))%=8.5% fluctuation in P(r) would provide adequate symmetry on 44% of the shots. We propose that three-dimensional radiative-magnetohydrodynamic simulations be performed to quantify the sensitivity of the x-ray emission to various initial conditions, and to determine whether an imploding z pinch is a spatiotemporal chaotic system.

Hot dense capsule-implosion cores produced by Z-pinch dynamic Hohlraum radiation

Hot dense capsule implosions driven by Z-pinch x rays have been measured using a approximately 220 eV dynamic Hohlraum to implode 1.7-2.1 mm diameter gas-filled CH capsules. The capsules absorbed up to approximately 20 kJ of x rays. Argon tracer atom spectra were used to measure the T(e) approximately 1 keV electron temperature and the n(e) approximately 1-4 x 10(23) cm(-3) electron density. Spectra from multiple directions provide core symmetry estimates. Computer simulations agree well with the peak emission values of T(e), n(e), and symmetry, indicating reasonable understanding of the Hohlraum and implosion physics.

Invasive Cancers Detected after Breast Cancer Screening Yielded a Negative Result: Relationship of Mammographic Density to Tumor Prognostic Factors

PURPOSE

To evaluate common breast tumor prognostic characteristics, including estrogen receptor (ER) status, grade, size, and method of detection, in relationship to mammographic density.

MATERIALS AND METHODS

The study involved 121 women who had negative results at both screening mammography and breast physical examination within 17 months before a diagnosis of breast cancer. Mammographic density was classified according to Breast Imaging Reporting and Data System patterns 1 through 4 (where 1 indicates a fatty breast and 4 indicates a dense breast). Axillary nodal status and tumor histologic ER status, histologic grade, size, stage, and method of detection (mammography alone, palpation alone, or both palpation and mammography) were analyzed by density category and tested for statistically significant differences across categories by using analysis of variance.

RESULTS

Statistically significant differences (P <.05) by density category were found for the following variables: ER positivity (15 of 15 tumors in category 1 breasts, 32 of 41 tumors in category 2 breasts, 37 of 49 tumors in category 3 breasts, and eight of 16 tumors in category 4 breasts were ER positive), occurrence of grade 1 tumors (eight, 11, 19, and four tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were grade 1), mean tumor size (11.3, 13.0, 14.7, and 19.7 mm for category 1, category 2, category 3, and category 4 breasts, respectively), detection with mammography alone (13, 31, 36, and four tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were detected with mammography alone), and occurrence of stage I tumors (10, 25, 28, and five tumors in category 1, category 2, category 3, and category 4 breasts, respectively, were stage I).

CONCLUSION

In women with negative results at clinical and mammographic screening within 17 months before breast tumor detection, subsequently diagnosed cancers tend to be ER negative, of higher grade, and larger in size in those with dense tissue patterns than in those with fat patterns.

Does the brain noradrenaline network mediate the effects of the CO2 challenge?

The inhalation of carbon dioxide (CO2) is commonly used in patients and volunteers as a means of producing anxiety or panic. It is generally believed that patients with panic disorder are more vulnerable to the effects of CO2 than patients with other anxiety disorders or healthy volunteers and there is speculation and debate as to the mechanism for this apparent sensitivity. Recent work from our group has shown that a single inhalation of 35% CO2 activates the hypothalamic-pituitary-adrenocortical (HPA) axis, increases blood pressure (BP) and increases subjective fear responses in healthy volunteers. Correlation analyses reveal a relationship between the changes in BP and the cortisol increase. These findings led us to postulate that a common mechanism may mediate these and the subjective responses to inhalation of CO2. We propose that the noradrenergic system, particularly the locus coeruleus (LC), but including the A1 and A2 cell groups, may be a key mediator of these responses. This article examines the evidence and discusses the results of studies from our laboratory in relation to a neuroanatomical model centring on the LC.

Use of a wave reverberation technique to infer the density compression of shocked liquid deuterium to 75 GPa

A novel approach was developed to probe density compression of liquid deuterium (L-D2) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22-75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.

Effects of 5 weeks of administration of fluoxetine and dothiepin in normal volunteers on sleep, daytime sedation, psychomotor performance and mood

This was a placebo-controlled, double-blind randomized crossover study of long-term (5 weeks) administration of fluoxetine (20 mg/day) and dothiepin (75 mg/day for 1 week followed by 150 mg/day for 4 weeks) in 12 healthy male volunteers. Subjects were studied on day 10 and day 36 of treatment, with tests of nocturnal sleep, driving performance, continuous electroencephalogram (EEG), sleep during scheduled naps, computerized visual attention tasks, saccadic eye movement measurement and visual analogue ratings of mood. Both drugs had a marked suppressive effect on nocturnal rapid eye movement (REM) sleep; these effects were less at 36 days than at 10 days, and fluoxetine decreased and dothiepin increased REM in daytime naps. Sleep fragmentation after fluoxetine is similar to that reported in the literature. We found no sleep-promoting effects of dothiepin, in contrast to our previous single-dose study, and no subjective sleep effects of either drug. Subjects were less sleepy after both antidepressants than placebo at 5 weeks measured by sleep latencies and EEG. Saccadic eye movement measures were significantly faster after 5 weeks of fluoxetine than after 5 weeks of placebo. Reaction times to a peripheral stimulus during computerized tracking task were shorter after 10 days of dothiepin compared with placebo. Driving performance, visual attention and mood ratings showed no treatment effects. Subjective health reports during each 5 weeks of treatment were similar in number for the two drugs but showed a different profile of side-effects.

Resistance of Peanut to Sclerotinia Blight and the Effect of Acibenzolar-S-methyl and Fluazinam on Disease Incidence

Sclerotinia minor, a soilborne fungal pathogen of peanut, can cause serious yield loss in North Carolina. A field test was implemented to study genotype reaction, and the effect of aciben-zolar-S-methyl (a plant activator) and the fungicide fluazinam on disease incidence. In all, 13 genotypes in 1997 and 12 genotypes in 1998 were evaluated. Three applications of acibenzolar-S-methyl (0.14 kg a.i./ha) or fluazinam (0.58 kg a.i./ha) were made on a calendar-based schedule. Disease ratings were made weekly in 1997 and every other week in 1998. Fluazinam suppressed disease at all sites and increased yield at two of three locations. Acibenzolar-S-methyl had no effect on disease incidence or yield. The advanced breeding line N92056C and cvs. Tam-run 98 (TX 901417) and Perry (N93112C) had moderate to high levels of resistance to S. minorand produced high yields compared with susceptible cv. NC 7. Lines derived from wild species also demonstrated moderate to high levels of resistance relative to NC 7 and represent potential breeding lines.

X-ray absorption spectroscopy measurements of thin foil heating by Z-pinch radiation

Absorption spectroscopy measurements of the time-dependent heating of thin foils exposed to intense z-pinch radiation sources are presented. These measurements and their analysis provide valuable benchmarks for, and insights into, the radiative heating of matter by x-ray sources. Z-pinch radiation sources with peak powers of up to 160 TW radiatively heated thin plastic-tamped aluminum foils to temperatures approximately 60 eV. The foils were located in open slots at the boundary of z-pinch hohlraums surrounding the pinch. Time-resolved Kalpha satellite absorption spectroscopy was used to measure the evolution of the Al ionization distribution, using a geometry in which the pinch served as the backlighter. The time-dependent pinch radius and x-ray power were monitored using framing camera, x-ray diode array, and bolometer measurements. A three-dimensional view factor code, within which one-dimensional (1D) radiation-hydrodynamics calculations were performed for each surface element in the view factor grid, was used to compute the incident and reemitted radiation flux distribution throughout the hohlraum and across the foil surface. Simulated absorption spectra were then generated by postprocessing radiation-hydrodynamics results for the foil heating using a 1D collisional-radiative code. Our simulated results were found to be in good general agreement with experimental x-ray spectra, indicating that the spectral measurements are consistent with independent measurements of the pinch power. We also discuss the sensitivity of our results to the spectrum of the radiation field incident on the foil, and the role of nonlocal thermodynamic equilibrium atomic kinetics in affecting the spectra.

Bioprocess applications of a Sindbis virus-based temperature-inducible expression system

The production and study of toxic proteins requires inducible expression systems with low basal level expression and high inducibility. Here, we describe bioprocess applications of the pCytTS temperature-regulatable Sindbis virus replicon-based expression system. We used green fluorescent protein as a marker protein to optimize the selection of stable transfected clones with increased expression levels. Using the optimized protocol, clones were constructed that produced the growth-inhibiting, anti-viral protein interferon beta (beta-IFN). Selected clones were analyzed for temperature-dependent beta-IFN production in adherent and suspension cultures in serum free medium. Specific expression levels were around 1.0 x 10(5) IU/10(6) cells/day (0.5 microg/10(6) cells/day) in suspension cultures and over 1.5 x 10(6) IU/mL/day (7.5 microg/mL/day) in hollow fiber reactors using adherent cells. Hexahistidine-tagged beta-IFN purified from T-flask cultures was highly glycosylated and showed high specific activity. beta-IFN mRNA amplified by the viral replicase for 10 days did not show an accumulation of mutations. These data suggest the applicability of the pCytTS-inducible expression system for the production of high-quality glycoproteins in different reactors.

Analysis of fermentation processes using flow microfluorometry: Single-parameter observations of batch bacterial growth

The laser flow microfluorometer (FMF) can determine the amounts of certain components in single cells at sample rates of several thousand cells per second. This technique has been employed to characterize Bacillus subtilis populations in batch fermentations with different inocula. Protein and nucleic acid distributions obtained by FMF analyses at different times during the batch have been decomposed using an optimized fit of summed subpopulation distributions. The results of these decomposition calculations, some of which have been approximately confirmed by independent microscopic observations, indicate that the relative numbers of single rods, cell chains, spores, and swollen rounded cells change dramatically during the entire fermentation including the stationary phase. The dynamics of these subpopulations may be related to secondary metabolite production.

X-ray imaging measurements of capsule implosions driven by a Z-pinch dynamic hohlraum

The radiation and shock generated by impact of an annular tungsten Z-pinch plasma on a 10-mm diam 5-mg/cc CH(2) foam are diagnosed with x-ray imaging and power measurements. The radiative shock was virtually unaffected by Z-pinch plasma instabilities. The 5-ns-duration approximately 135-eV radiation field imploded a 2.1-mm-diam CH capsule. The measured radiation temperature, shock radius, and capsule radius agreed well with computer simulations, indicating understanding of the main features of a Z-pinch dynamic-hohlraum-driven capsule implosion.

Mammographic screening of TRAM flap breast reconstructions for detection of nonpalpable recurrent cancer

PURPOSE

To evaluate findings from routine mammographic screenings in patients with transverse rectus abdominis musculocutaneous (TRAM) flap reconstructions.

MATERIALS AND METHODS

During a 25-month study period, 214 consecutive screening mammograms in 113 asymptomatic women (mean age, 51 years) with TRAM flap reconstructions were obtained. Mastectomies were performed for cancer in 106 (94%) of the 113 women and for prophylaxis in seven (6%). Prospectively, a Breast Imaging Reporting and Data System (BI-RADS) assessment category 1-5 was assigned to each mammogram. Surgical, medical, pathologic, and radiographic records were retrospectively reviewed. CIs were determined by the normal approximation to the binomial distribution.

RESULTS

Seven (3%) of 214 examinations were BI-RADS category 4 or 5. Six (86%) of seven patients underwent biopsy. Two (33%) of these six biopsies demonstrated invasive ductal carcinoma. Cancer detection rate for mammography was 1.9% (two of 106) (95% CI: 0.33%, 7.32%) for women with reconstruction for breast cancer during the 2-year period. One (6%) of 16 BI-RADS category 3 examinations later proved to be invasive ductal carcinoma at follow-up. No interval cancer was discovered in 171 cases of BI-RADS category 1 or 2 examinations with 1-year follow-up. No cancers occurred in women who underwent prophylactic mastectomy. A biopsy positive predictive value of 33% (95% CI: 6%, 76%) was observed.

CONCLUSION

Screening mammography of TRAM flap-reconstructed breasts enables detection of nonpalpable cancer before clinical examination.

Metabolic flux responses to pyruvate kinase knockout in Escherichia coli

The intracellular carbon flux distribution in wild-type and pyruvate kinase-deficient Escherichia coli was estimated using biosynthetically directed fractional 13C labeling experiments with [U-13C6]glucose in glucose- or ammonia-limited chemostats, two-dimensional nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids, and a comprehensive isotopomer model. The general response to disruption of both pyruvate kinase isoenzymes in E. coli was a local flux rerouting via the combined reactions of phosphoenolpyruvate (PEP) carboxylase and malic enzyme. Responses in the pentose phosphate pathway and the tricarboxylic acid cycle were strongly dependent on the environmental conditions. In addition, high futile cycling activity via the gluconeogenic PEP carboxykinase was identified at a low dilution rate in glucose-limited chemostat culture of pyruvate kinase-deficient E. coli, with a turnover that is comparable to the specific glucose uptake rate. Furthermore, flux analysis in mutant cultures indicates that glucose uptake in E. coli is not catalyzed exclusively by the phosphotransferase system in glucose-limited cultures at a low dilution rate. Reliability of the flux estimates thus obtained was verified by statistical error analysis and by comparison to intracellular carbon flux ratios that were independently calculated from the same NMR data by metabolic flux ratio analysis.