cssi/SciSciGPT-SciSciNet huggingface dataset:
Single-Molecule Observation of Viral DNA Targeting by CRISPR/Cas Immune Systems

Bacteria and archaea maintain a history of viral infections by integrating small fragments of foreign DNA into specialized genomic loci called clustered regularly interspaced short palindromic repeats (CRISPRs). An adaptive immune response is triggered during subsequent infections by CRISPR-derived RNAs (crRNAs), which function together with CRISPR-associated (Cas) proteins to identify and destroy complementary viral DNA sequences. DNA targeting by crRNA/Cas ribonucleoprotein surveillance complexes proceeds via RNA-DNA base-pairing interactions and requires melting of the double-stranded substrate, as well as protein-mediated recognition of a proximal DNA sequence motif to discriminate self from non-self. How these complexes find short target sequences within the larger context of genomic DNA is unknown, and prior studies have been limited by their use of oligonucleotide substrates and dependence on bulk electrophoretic mobility shift assays that obscure all dynamics of the search process. To gain deeper insights into this critical step of CRISPR/Cas based immunity, we are using fluorescence microscopy to visualize single crRNA/Cas complexes on nanofabricated curtains of viral DNA in real-time. These experiments enable direct observation of the kinetics and position-dependence of DNA binding, and have revealed the mechanism by which phylogenetically distinct surveillance complexes use sequence information in the crRNA to locate complementary DNA targets. Ongoing work is aimed at understanding how this recognition event promotes destruction of viral DNA by dedicated Cas nucleases.
Intensive intervention improves primary care follow-up for uninsured emergency department patients.

Objectives: To test an intervention designed to improve primary care use and decrease emergency department (ED) utilization for uninsured patients using the ED. Methods: Using a randomized design, an intensive case-management intervention was tested with patients identified at a Level 1 urban trauma center from April 2002 through July 2002. Following assessment in the ED, six-month follow-up data were gathered from four primary care sites (two Federally Qualified Health Centers, two hospital outpatient clinics) and two area hospitals. Eligible participants were uninsured, were at least 18 years of age, and did not have a regular primary care provider. Of 281 patients approached, 273 (97.2%) agreed to participate. After 42 patients were eliminated following enrollment due to ineligibility, there were 121 intervention and 109 comparison subjects. Health Promotion Advocates (HPAs) in the ED gathered information from all study participants. On intervention shifts, HPAs assisted patients in choosing a primary care provider and faxed all information to a case worker at the selected site. Case managers attempted to contact patients and schedule appointments. On comparison shifts, patients received care as usual. Primary care contact in 60 days and subsequent ED visits in six months post-ED assessment were the main outcome measures. Results: Intervention subjects were more likely to have a primary care contact (51.2% vs. 13.8%, p < 0.0001). There was no statistically significant difference between groups in either number of inpatient admissions or postintervention ED visits, although postintervention ED visits for the intervention group were less expensive. Conclusions: This project has demonstrated that it is possible to improve primary care follow-up for uninsured ED patients.
Dual regulatory role for thyroid-hormone receptors allows control of retinoic-acid receptor activity

BOTH thyroid hormone (T3) and retinoic acid signal essential steps in development, differentiation and morphogenesis. Specific nuclear receptors for these ligands have recently been cloned1-8. Previously we have noted a close homology between the DNA-binding domains of the e-retinoic acid receptor (RAR-e, also designated RAR-β), the thyroid hormone receptors and the oes-trogen receptor2,9. We have now found that RAR-e is very efficient at inducing transcription from two distinct thyroid-hormone responsive elements (TREs). Transcription induced by ligand-activated RAR-e from a TRE can, however, be repressed by thyroid-hormone receptor in the absence of its ligand. Conversely, in the presence of its ligand, thyroid-hormone receptor will activate tran-scription from a TRE irrespective of the presence of unbound RAR. The use of hybrid receptors has shown that the DNA-binding domain of RAR is the essential target for inhibition by thyroid-hormone receptors. These data, together with in vitro DNA-binding studies, suggest that thyroid-hormone receptors may have dual regulatory roles: in the presence of hormone they function as TRE-specific transcriptional activators; in the absence of hormone, however, they can function as TRE-specific repressers.
Fast parameterless density-based clustering via random projections

Clustering offers significant insights in data analysis. Density based algorithms have emerged as flexible and efficient techniques, able to discover high-quality and potentially irregularly shaped- clusters. We present two fast density-based clustering algorithms based on random projections. Both algorithms demonstrate one to two orders of magnitude speedup compared to equivalent state-of-art density based techniques, even for modest-size datasets. We give a comprehensive analysis of both our algorithms and show runtime of O(dNlog2N), for a d-dimensional dataset. Our first algorithm can be viewed as a fast variant of the OPTICS density-based algorithm, but using a softer definition of density combined with sampling. The second algorithm is parameter-less, and identifies areas separating clusters.
Biocompatibility of Synthetic Poly(Ester urethane)/Polyhedral Oligomeric Silsesquioxane Matrices with Embryonic Stem Cell Proliferation and Differentiation

Incorporation of polyhedral oligomeric silsesquioxanes (POSS) into poly (ester urethane)s (PEU) as a building block results in a PEU/POSS hybrid polymer with increased mechanical strength and thermostability. An attractive feature of the new polymer is that it forms a porous matrix when cast in the form of a thin film, making it potentially useful in tissue engineering. In this study, we present detailed microscopic analysis of the PEU/POSS matrix and demonstrate its biocompatibility with cell culture. The PEU/POSS polymer forms a continuous porous matrix with open pores and interconnected grooves. From SEM image analysis, it is calculated that there are about 950 pores per mm 2 of the matrix area with pore size ranging from 1 to 15 μm in diameter. The area occupied by the pores represents approximately 7.6 % of matrix area. Using mouse embryonic stem cells (ESCs), we demonstrate that the PEU/POSS matrix provides excellent support for cell proliferation and differentiation. Under the cell culture condition optimized to maintain self-renewal, ESCs grown on a PEU/POSS matrix exhibit undifferentiated morphology, express pluripotency markers, and have similar growth rate to cells grown on gelatin. When induced for differentiation, ESCs underwent dramatic morphological change, characterized by the loss of clonogenecity and increased cell size with well-expanded cytoskeleton networks. Differentiated cells are able to form a continuous monolayer that is closely embedded on the matrix. The excellent compatibility between the PEU/POSS matrix and ESC proliferation/ differentiation demonstrates the potential of using PEU/POSS polymers in future ESC-based tissue engineering.
Size variation in the postcranium ofAustralopithecus afarensis and extant species of hominoidea

The postcranial sample ofA. afarensis can be divided into two size groups. Among the best preserved elements which are represented by both morphs are the distal femur, proximal ulna, and capitate. The difference between the large and small fossil femora is similar to the difference between average male and femaleG. gorilla andP. pygmaeus. The distal femora ofH. sapiens are less sexually dimorphic while those ofP. paniscus, P. troglodytes, andH. lar are not significantly dimorphic at all. Large and small capitates and proximal ulnae ofA. afarensis differ slightly more than the highly dimorphic species of extant Hominoidea. In my sample of Amerindians, the capitate and proximal ulna are also strongly dimorphic. The two species ofPan have insignificant sexual dimorphism in these traits.
Crystal structure of W[C(CMe3)C(Me)C(Me)]Cl3, the archetypal example of a planar delocalized tungstenacyclobutadiene complex

Abstract The complex W[C(CMe 3 )C(Me)C (Me)]Cl3 has been subjected to a single-crystal X-ray diffraction study. The complex crystallizes in the centrosymmetric monoclinic space group P21/c (No. 14) with a 10.2710(22), b 10.1132(21), c 12.7205(26) A, gb 96.099(17)°, V 1313.8(5) A3 and D(calcd) 2.09 g cm−3 for mol. wt. 413.43 and Z = 4. Diffractometer data were collected for reflections with 2θ = 3.7–50.0° (Mo-Kα) and the structure was solved and refined to RF 4.6% for 2327 data. The tungsten atom has a distorted trigonal bipyramidal coordination geometry. Two chloride ligands are in axial sites (WCl(1) 2.404(2), WCl(2) 2.394(2) A), while the third occupies an equatorial position (WCl(3) 2.330(3) A). The tungstenacyclobutadiene system, WC(1)C(6)C(7), is planar and occupies two equatorial sites. The WC(α) linkages (WC(1) 1.861(9), WC(7) 1.864(8) A) are equivalent, as are the C(α)-C(β) bond lengths (C(1)C(6) 1.455(13), C(6)C(7) 1.478(12) A).
Ultrastructure of the frontal ganglion of Chaoborus and observations on neurosecretory cells during the annual cycle

Abstract The frontal ganglion contains approximately 20 cells and rests on the two posterior elevator muscles of the roof of the pharynx, thus locating the ganglion ventral and anterior to the brain. Two frontal nerves, a pair of lateral connectives, and the single recurrent nerve connect with the ganglion. There is a centrally located neuropile which is surrounded by the perineurium which in turn is covered by the neural lamella. The perineruium contains numerous glial cells and neurons with two large neurosecretory cells located in a dorsal lateral position of the ganglion. The neurosecretory cells were examined on five occasions during the year, and no significant changes occurred in the fine structure of the organelles or cellular products. The cells appear to be engaged in the synthesis of elementary neurosecretory granules throughout the year. This observation differs from previous studies on diapausing lepidopterous larvae and pupae. Axons from these two cells enter the lateral connectives and extend toward the protocerebrum.
Using Corporate-Based Methods to Assess Technical Communication Programs

Assessment continues to be an important issue for technical communicators in both practitioner and academic contexts. In this article, we investigate methods of program assessment used by corporate learning sites and we profile value add methods as a new way to both construct and evaluate academic programs in technical communication. Our goal is to introduce value added assessment methods as one way to supplement and expand current methods of program assessment. The article initially reviews Return on Investment (ROI) indicators as a widely used model for assessing programs. However, we are critical of these indicators, suggesting that they are biased against technical communication in both practitioner and academic contexts. The article then examines and critiques assessment methods from corporate training environments. These include methods employed by corporate universities and value added process-based assessment methods. The second half of the article profiles value added methods by applying them in a brief assessment of a technical communications certificate program. We conclude that while the program uses ROI indicators as a marketing device, the value the program brings and adds to its university is the portal it creates for university and business community collaboration. This value cannot be fully demonstrated solely through the use of ROI indicators. The article then discusses the kinds of programmatic negotiations value added processes require within university contexts that may impose non-value added activities on departments and programs. The article concludes by critically examining the appropriateness of corporate assessment methods for academic contexts.
Titanium−Carbon Clusters: New Evidence for High Stability of Neutral Met-Cars

The objective of the present study is to establish whether the neutral titanium metallocarbohedrene cluster (Met-Car), Ti8C12, has a high stability as does its cation counterpart. In this investiga...
A simple method for the assay of carbon-14 in compounds or mixtures.

A method is presented for the rapid and quantitative oxidation of water- soluble C/sup 14/ compounds or mixtures of compounds, to C/sup 14/-labeled CO/sub 2/. The C/sup 14/O/sub 2/ is absorbed into a carbonate-free NaOH solution. The C/sup 14/ may then be determined by precipitation of the C/sup 14/ as barium carbonate and counting. Total carbon is determined by titration of an aliquot of the NaOH-Na/sub 2/CO/sub 3/ mixture to both the phenolphthalein and brom cresyl green end-points. For the oxidation of samples of pure C/sup 14/-lactic acid, 800 mg K/sub 2/S/sub 2/O/sub 8/ was adequate for the complete and quantitative oxidation of amounts of lactic acid equivalent to 13 mg of carbon. Replicate resuIts for total carbon recovery on pure lactic acid solutions yielded recoveries of 97 to 100%, (M.C.G.)
K-centers Min-Max clustering algorithm over heterogeneous wireless sensor networks

This paper proposes a clustering algorithm for heterogeneous wireless sensor networks, addressing energy dissipation as a key issue. Energy dissipation required by sensor nodes to transmit data depends on the distance between sensor nodes and cluster heads or a base station. Clustering is one of the best techniques for reducing energy consumption and extending sensor network lifetimes. Desirable features of the proposed clustering algorithm include: adaptation to changes in sensor distribution; energy efficiency; localized and distributed data aggregation and decision making; immunity to partial damage; and self-recovery. It employs a smallest disc covering algorithm to achieve a minimum of the maximum distance between a cluster head and sensor nodes compared to k-means clustering. Lawson's multiplicative rule is used for the smallest disc covering algorithm. Our simulation demonstrates that the proposed algorithm takes 50.8% fewer iterations to converge for cluster formation, with 33.9% and 23.2% shorter maximum and average intra-cluster distances versus k-means clustering. Performance is also improved.
How Bid-Protest Mechanisms Mitigate Opportunism in Government Contracting

ABSTRACT This article proposes that government contracting, especially the source-selection process, gives rise to a particularly intractable set of transactional hazards: governmental opportunism and third-party opportunism. It shows how the first of these hazards can be addressed by third-party intervention and how third-party intervention leads to third-party opportunism. It argues that existing arrangements governing the source-selection process, primarily the GAO's bid-protest mechanism, mitigate the consequences of governmental opportunism and the direct harm resulting from third-party opportunism. More formally put, it concludes that the bid-protest mechanism works to minimize the maximum losses resulting from opportunistic behavior in the source-selection process. Therefore, existing governance arrangements are reasonably effective solutions to the idiosyncratic transactional hazards associated with source selection in government contracting.
Structural studies of ordered monolayers using atomic force microscopy

Abstract The invention of the atomic force microscope (AFM) in 1986 by Binnig, Quate and Gerber has provided researchers with a powerful tool for the investigation of surfaces of nonconductive materials. This technique is of special interest to biologists since, not only it is possible to image various surfaces, but since scanning can be done under a liquid, buffer solutions can be employed such that biological molecules can be imaged under physiologically realistic conditions. One increasingly popular application of AFM is the investigation of Langmuir-Blodgett (LB) films. These are thin organic layers formed by transferring a monolayer of amphiphiles from the surface of an aqueous subphase onto a solid substrate. Not only do LB films have possible applications in materials science and optics, but they provide model systems for the study of biological membranes. AFM has been used extensively in the investigation and characterization of both local bond ordering and overall film integrity in these quasi-two-dimensional structures. The local nature of this investigative technique can yield valuable information not provided by other methods.
Evaluating the Effectiveness of an Illustrated Permission/Assent Form

Issues of language and literacy represent a significant barrier to participation in clinical research. This study was designed to explore whether illustrating the permission/assent (P/A) document offers an alternative strategy for communicating study related information to underserved populations. Participants were verbally introduced to a mock study and asked to review the corresponding P/A form with companion pictorials. Questionnaires were used to examine whether the form addressed essential elements of a P/A (as defined under the Code of Federal Regulations) and evaluate the effectiveness of the companion pictures. Over 93% of participants agreed that the form addressed the required basic elements of a P/A. Pictures depicting study procedures were highly effective while images depicting nebulous concepts such as research and voluntariness were deemed less effective. The medical research community can expand enrollment opportunities to underserved populations by using visual aids to complement the informed consent process.
Incidence and severity of hand-foot syndrome in colorectal cancer patients treated with capecitabine: a single-institution experience.

Background: Hand–foot syndrome (HFS) has been previously reported as a side effect in 45–56% of patients treated with capecitabine. However, the natural history of HFS has not been fully characterized. In this study, we investigate the incidence, severity, and time course of HFS. Design: Toxicity data collected for 41 patients treated in two clinical trials were analyzed for the occurrence of HFS. Proportions of patients developing HFS after capecitabine treatment were calculated, and the severity and time course of HFS were analyzed. Results: Twenty-eight (68.3%) of the 41 patients had at least one episode of HFS. Most patients had their first (92.9%) or most severe (67.9%) episode of HFS within the first two cycles of treatment. Eighty-nine percent of the HFS episodes were grade 1 or 2; only 11% were grade 3. Conclusions: HFS is common in patients treated with capecitabine, and usually starts within the first two cycles of therapy.
Chain length dependent thermodynamics of saturated symmetric‐chain phosphatidylcholine bilayers

A molecular interpretation for the chain length dependent thermotropic behavior of saturated symmetric-chain phosphatidylcholine bilayers is proposed. It is suggested that the bilayer interface region and conformationally inequivalent terminal ends of the fatty acyl chains perturb the packing associations of the rest of the hydrocarbon chains in the gel phase of the bilayer. These perturbing effects, which are seen to increase with decreasing acyl chain length, have been quantitatively defined by a perturbation parameter, P. The thermodynamic parameters of the thermal phase transition of these phosphatidylcholines are found to be linearly correlated to P and these linear relationships can be used to predict the minimum number of carbon atoms in the acyl chain necessary in order for a bilayer phase transition to occur.
Endoscopic Management of Nonlifting Colon Polyps

Background and Study Aims. The nonlifting polyp sign of invasive colon cancer is considered highly sensitive and specific for cancer extending beyond the mid-submucosa. However, prior interventions can cause adenomas to become nonlifting due to fibrosis. It is unclear whether nonlifting adenomas can be successfully treated endoscopically. The aim of this study was to evaluate outcomes in a referral practice incorporating a standardized protocol of attempted endoscopic resection of nonlifting lesions previously treated by biopsy, polypectomy, surgery, or tattoo placement. Patients and Methods. Retrospective review of patients undergoing colonoscopy by one endoscopist at two hospitals found to have nonlifting lesions from prior interventions. Lesions with biopsy proven invasive cancer or definite endoscopic features of invasive cancer were excluded. Lesions ≥ 8 mm were routinely injected with saline prior to attempted endoscopic resection. Polypectomy was performed using a stiff snare, followed by argon plasma coagulation (APC) if necessary. Results. 26 patients each had a single nonlifting lesion with a history of prior intervention. Endoscopic resection was completed in 25 (96%). 22 required snare resection and APC. 1 patient had invasive cancer and was referred for surgery. The recurrence rate on follow-up colonoscopy was 26%. All of the recurrences were successfully treated endoscopically. There was 1 postprocedure bleed (4%), no perforations, and no other complications. Conclusions. The majority of adenomas that are nonlifting after prior interventions can be treated successfully and safely by a combination of piecemeal polypectomy and ablation. Although recurrence rates are high at 26%, these too can be successfully treated endoscopically.
Numerical modeling of tidal currents and the effects of power extraction on estuarine hydrodynamics along the Georgia coast, USA

The tidal stream power potential along the coast of the state of Georgia is evaluated based on numerical modeling and validated with the available data. The Georgia coast consists of a complex network of tidal rivers and inlets between barrier islands that funnel and locally amplify the strength of the ambient tidal currents in the region. The number of existing tidal current prediction locations is not sufficient to resolve the temporal and spatial changes in the current speeds and patterns. Therefore, the currents are modeled with the Regional Ocean Modeling System (ROMS) to determine the locations with high tidal stream power potential and the results are validated against measurements. The wetlands and the topographical features are integrated in the computational model with wetting and drying of computational cells. The locations with the largest mean tidal stream power density are identified and their characteristics are provided. The effect of power extraction on estuarine hydrodynamics is simulated by implementing an additional retarding force in the governing momentum equations in ROMS. Two different power extraction schemes are simulated at the Canoochee River. The first scheme involves extracting 20% of the original kinetic power across the entire cross-section of the river, and is found to have substantially lower impact on the original flow than the second scheme with 45% extraction. The summation of removed and residual kinetic powers is found to be larger than the original kinetic power in the cross-section, which is attributed to the recovery in the flow momentum through reorganization of stream flow energy. In both of the cases the major impact on the currents is limited to a partial reach of the river. The change in the maximum and minimum water levels is observed to be on the order of centimeters.
Kinesin and Dynein-Dynactin at Intersecting Microtubules: Motor Density Affects Dynein Function

Kinesin and cytoplasmic dynein are microtubule-based motor proteins that actively transport material throughout the cell. Microtubules can intersect at a variety of angles both near the nucleus and at the cell periphery, and the behavior of molecular motors at these intersections has implications for long-range transport efficiency and accuracy. To test motor function at microtubule intersections, crossovers were arranged in vitro using flow to orient successive layers of filaments. Single kinesin and cytoplasmic dynein-dynactin molecules fused with green-fluorescent protein, and artificial bead cargos decorated with multiple motors, were observed while they encountered intersections. Single kinesins tend to cross intersecting microtubules, whereas single dynein-dynactins have a more varied response. For bead cargos, kinesin motion is independent of motor number. Dynein beads with high motor numbers pause, but their actions become more varied as the motor number decreases. These results suggest that regulating the number of active dynein molecules could change a motile cargo into one that is anchored at an intersection, consistent with dynein's proposed transport and tethering functions in the cell.
Inhibition of Calsequestrin Phosphorylation Leads to its Trafficking from Rough Endoplasmic Reticulum

Calsequestrin 2 (CSQ) is a protein in heart cells that concentrates within the sarcoplasmic reticulum (SR), where it incorporates into Ca2+-release complexes. CSQ has a single N-linked glycan that can be used to determine the extent of its trafficking through the secretory system, and multiple C-terminal protein kinase CK2 sensitive phosphorylation sites. Recent data suggests that polymerization of CSQ defines its localization, and leads to its retention within discrete secretory compartments. In these studies, we show that phosphorylation may be responsible for localization of cardiac CSQ within the rough ER of nonmuscle cells and cardiomyocytes. Triple point mutations were made to wild-type canine CSQ (CSQ-WT) phosphorylation sites, either mimicking (CSQ-aPP, S378,382,386E) or inhibiting phosphorylation (CSQ-nPP, S378,382,386A). Overexpression into COS cells showed that, compared to CSQ-WT, mannose trimming of the CSQ glycan increased for CSQ-nPP, reflecting movement out of rough ER; whereas no change was seen for CSQ-aPP. This apparent phosphorylation-dependent change in subcellular localization in COS cells could be observed by confocal immunofluorescence microscopy. The CK2 specific inhibitor tetrabromocinnamic acid (TBCA) blocks phosphorylation of CSQ in vitro by CK2 or by endogenous CSQ kinases with an identical dose response, supporting the identity of CK2 as the CSQ kinase. TBCA (100μM) also inhibited phosphorylation in cultured cells by roughly 80%. Analysis of CSQ overexpressed in these cells showed an effect on CSQ trafficking that was highly similar to the effects of the phosphorylation-site mutant CSQ-nPP. These data support a hypothesis that CSQ phosphorylation by protein kinase CK2 acts to retain cardiac CSQ in rough ER. In cardiomyocytes, growth-dependent phosphorylation of CSQ produces rough ER retention resulting in redistribution of CSQ from junctional SR to the nuclear envelope, the site of IP3-dependent ER Ca2+ storage.
Qualitative assessment of study materials and communication strategies used in studies that include DNA collection.

To understand motivations and barriers to participation in studies that include DNA collection, focus group discussions were held with mothers who had participated in a case–control study of birth defects. Recruited mothers had completed an interview and had received a mailed kit containing cytobrushes to collect buccal cells for DNA from herself, her infant, and her infant's father. Six moderator-led focus groups were attended by a total of 38 women residing in Atlanta, Georgia. Focus groups were segmented by DNA collection status (biologics participants or nonparticipants), infant case–control status, infant birthweight, and maternal race and ethnicity. This report assesses maternal attitudes toward study materials and communication strategies. Across groups, respondents expressed concern about how their contact information was obtained. Study materials were described as clear and professional by most women, although some respondents reported confusion about disclosure of individual genetic results. Respondents generally reported that monetary incentives were not a motivation to participate, but increased perceived study legitimacy. Biologics nonparticipants expressed concerns about kit component sterility; government involvement; and DNA sample use, storage, and disposal. Respondents suggested that investigators provide feedback on whether sample collection was performed correctly and provide materials targeted to fathers to help alleviate paternal skepticism. Participation in DNA collection might be improved by strengthening study materials and communication strategies. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.
Tight junction dynamics: is paracellular transport regulated?

The tight junction, or zonula occludens (ZO), is a narrow belt-like structure on the plasma membrane of transporting epithelial cells that circumferentially wraps each cell and adjoinsit with its neighbors. In general, the ZO resides at the apical pole of the cell and separates the apical and basolateral plasma membranes (figure). Focally within this ZO belt, the lateral membranes of adjacent cells closely approximate one another. These sites of intimate contact, colloquially termed membrane “kisses:’ are thought to represent the physical sites at which diffusion of molecules across the ZO is impeded. As viewed en face in replicas of freeze-fractured plasma membranes, the ZO appears as an anastamosing web of strands. These strands represent the kiss sites and thus allow one to trace the course of the kisses along the plane of the lateral membrane (see Gumbiner, Am. J. Physiol. 253, C749-C758, 1987). The ZO has two known functions. First, by helping to restrict specific transporters, pumps, and channels to either the apical or basolateral membrane domains, it assists in-but is not solely responsible for-the maintenance of the surface polarity required for vectorial transepithelial transport processes (e.g., salt absorption). Second, by acting as a diffusion barrier, it helps retain the differences in extracellular fluid composition that exist across epithelia as a result of vectorial transport. There are only two pathways by which molecules can cross the epithelium: the transcellular and the paracellular (figure). The ZO appears to be the rate-limiting barrier that restricts flow through the paracellular pathway. It is now generally agreed that the ZO is a relative. rather than an absolute, barrier. For example, the electrical resistance of epithelia from different tissues can vary by two orders of magnitude, and these differences are thought largely to reflect variations in ZO ion permeability (see Powell, Minireview
Modeling the CAPTEX Vertical Tracer Concentration Profiles

Abstract Perfluorocarbon tracer concentration profiles measured by aircraft 600–900 km downwind of the release locations during CAPTEX are discussed and compared with some model results. In general, the concentrations decreased with height in the upper half of the boundary layer where the aircraft measurements were made. The results of a model sensitivity study suggested that the shape of the profile was primarily due to winds increasing with height and relative position of the sampling with respect to the upwind and downwind edge of the plume. Further modeling studies showed that relatively simple vertical mixing parameterizations could account for the complex vertical plume structure when the model had sufficient vertical resolution. In general, the model performed better with slower winds and corresponding longer transport times.
Tyrosine phosphatase CD45 is essential for coupling T-cell antigen receptor to the phosphatidyl inositol pathway

Stimulation of T lymphocytes through their antigen receptor (T-cell receptor; TCR) results in the activation of a tyrosine kinase and the generation of phosphatidyl inositol (PtdIns)-derived second messengers. Several reports have indicated that CD45, a haematopoietic cell-specific surface glycoprotein with tyrosine phosphatase activity in its cytoplasmic domain, is important in lymphocyte activation. To examine the possibility that CD45 might influence proximal signal transduction events through the TCR, we have isolated a variant of the human T-cell leukaemic line, HPB-ALL, which fails to express this phosphatase. Unlike cells expressing CD45, stimulation of the TCR in the CD45-negative cell does not result in PtdIns-derived second messengers. Reconstitution of CD45 expression restored early signalling events through the TCR. To localize the site of CD45 action, the human muscarinic type 1 receptor, which also activates the PtdIns second messenger pathway, was transfected into the CD45-negative cell. Although stimulation of the TCR failed to generate PtdIns-derived second messengers, there was normal activity of the PtdIns pathway when human muscarinic receptor type 1 was stimulated, despite the absence of CD45. These data indicate that CD45 influences a cellular component that is essential for effective coupling of the TCR to the PtdIns second messenger pathway.
cis-Acting Sequences 5E, M, and 3E Interact To Contribute to Primer Translocation and Circularization during Reverse Transcription of Avian Hepadnavirus DNA

Hepadnaviral reverse transcription requires template switches for the genesis of relaxed circular (RC) DNA, the major genomic form in virions. Two template switches, primer translocation and circularization, are required during the synthesis of the second, or plus, strand of DNA. Studies of duck hepatitis B virus (DHBV) indicate that in addition to the requirement for repeated sequences at the donor and acceptor sites, template switching requires at least three other cis-acting sequences, 5E, M, and 3E. In this study we analyzed a series of variant heron hepatitis B viruses (HHBV) in which the regions of the genome that would be expected to contain 5E, M, and 3E were replaced with DHBV sequence. We found that all single and double chimeras were partially defective in the synthesis of RC DNA. In contrast, the triple chimera was able to synthesize RC DNA at a level comparable to that of unchanged HHBV. These results indicate that the three cis-acting sequences, 5E, M, and 3E, need to be compatible to contribute to RC DNA synthesis, suggesting that these sequences interact during plus-strand synthesis. Second, we found that the defect in RC DNA synthesis for several of the single and double chimeric viruses resulted from a partial defect in primer translocation/utilization and a partial defect in circularization. These findings indicate that the processes of primer translocation and circularization share a mechanism during which 5E, M, and 3E interact.
Rearrangement of symmetrical dicubane clusters into topological analogues of the P cluster of nitrogenase: nature's choice?

Reaction schemes have been developed that lead to clusters having the topology of the PN cluster of nitrogenase. The single cubane clusters [(Tp)MFe3S4Cl3]z (M = Mo, z = 1−; M = V, z = 2−) react with PEt3 to give [(Tp)MFe3S4(PEt3)3]1+, which are reduced to the neutral edge-bridged double cubanes [(Tp)2M2Fe6S8(PEt3)4] with highly reduced (2[MFe3S4]1+) cores. Reaction of these clusters in acetonitrile with (Et4N)(HS) results in the formation of [(Tp)2Mo2Fe6S9(SH)2]3- and [(Tp)2V2Fe6S9(SH)2]4-. X-ray structures of the Et4N+ salts reveal the bridging pattern M2Fe6(μ2-S)2(μ3-S)6(μ6-S) in which two cuboidal MFe3(μ3-S)3 units share the common bridge atom μ6-S and are externally bridged by two μ2-S atoms. The M sites possess trigonal octahedral, and the Fe sites, distorted tetrahedral coordination. Hydrosulfide ligands and sulfide atoms simulate terminal cysteinate ligation and μ2 bridges, respectively, in the protein-bound cluster Fe8S7(μ2-SCys)2(SCys)4. The synthetic clusters have the same bridging pattern as t...
A testable CMOS asynchronous counter

A testable design for an asynchronous n-bit CMOS counter is presented, with test inputs that provide full coverage for stuck-at and stuck-open faults. The test time is O(n) where the counter outputs are not observable, compared to O(n/sup 2/) for a synchronous counter. Three control signals are required for the testable counter as opposed to one reset signal for the base counter. The testable counter incorporates a scan path, utilizing the state storage in the counter cells, whereby the counter is converted into an n-bit master-slave asynchronous shift register with the counter's request input being used as the shift-register input. The only observable outputs are acknowledge and carry-out signals. The counter utilizes two-cycle (transition) signaling and guarantees that new output values are available before acknowledge is toggled. Two 16-b counters, one base design and one scan-based design, were fabricated on the same chip (2.0- mu m n-well CMOS) through MOSIS. Four parts were received, all of which passed the test suites developed. >
The effects of an enhanced inflammatory reaction on the surface properties of cast biomer

The ability of a biomaterial to withstand the rigors of the harsh biologic environment is an important consideration when considering a material for long-term biomedical applications. Using a cage implant system, the effects of an intense inflammatory reaction on cast Biomer have been investigated. The inflammatory response to cast Biomer was greatly increased by coimplanting Biomer films with a cytotoxic poly(vinyl chloride) (PVC) in rats for a period of 21 days. Cast Biomer films were characterized by weight, advancing contact angle with water in air, attenuated total reflectance infrared spectroscopy and scanning electron microscopy (SEM). The analyses were performed before any treatment, after autoclaving and sonication, and after 21 days implantation with the cytotoxic (PVC) in rats. The results of the study indicated that cast Biomer does not undergo significant chemical degradation when subjected to the effects of an intense inflammatory reaction for 21 days. Implantation does, however, lead to rearrangement that results in a more polar and hydrophilic surface, suggesting that the polymer adapts to the hydrophilic environment of the inflammatory exudate.
Genetic engineering in agriculture: hydrogen uptake (hup) genes

Abstract Molecular hydrogen (H 2 ), an energy-rich product of the metabolism of many microorganisms, can be utilized by a variety of bacteria which have evolved hydrogen uptake ( hup ) genes. The hup genes play an important role in plant productivity by recycling the considerable quantities of reducing equivalents (in the form of H 2 ) wasted during symbiotic nitrogen fixation of leguminous crops such as soybean. Attempts are being made to introduce the energy-saving hup genes into root nodule bacteria. This work, described briefly in a previous review ( TIBS , Feb., 1980, 35–39) is described here in greater detail.
Isotropic, nematic and smectic A phases in fluids of hard spherocylinders

A phase diagram with accompanying order parameters has been calculated for the fluid phases of hard spherocylinders with perfect and partial orientational order as a function of the spherocylinder length to width ratio. The predictions are based on an Onsager/density functional theory (DFT), equipped with the exact excluded volume and a somewhat ad hoc resummation of the three and higher particle correlations. For perfectly aligned spherocylinders, the (N) nematic to (SmA) smectic A transition is rendered in basic accord with that of previous workers. When rotational disorder is permitted, the calculation becomes sensitive to different implementations of DFT. Although the calculated isotropic, nematic, smectic A triple point agrees with those of other workers, the location of the N-SmA critical point remains elusive. Present evidence suggests that the N-SmA transition becomes continuous only in the limit of highly aligned systems, where there is no orientational order to be gained.
BCNU and X-ray therapy of intracerebral 9L rat tumors

Abstract Combination therapy of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and X-rays was applied to the 9L rat brain tumor model. BCNU alone (13.3 mg/kg) and X-rays alone (2,000 rad/whole brain) were given on day 16 postimplant. The two therapies were combined in three schedules with BCNU given 6 hours before, 6 hours after, and immediately preceding X-ray treatment. While either modality alone significantly increased survival, the combined therapies produced increased life spans (ILS) of 235 to 430%. The combined therapies also resulted in cure rates as high as 60%. Some toxicity was encountered as evidenced by interstitial pulmonary fibrosis when “cured” and treated non-tumor bearing animals were autopsied on day 122 or day 125.
Protein complex of Drosophila ATRX/XNP and HP1a is required for the formation of pericentric beta-heterochromatin in vivo.

ATRX belongs to the family of SWI2/SNF2-like ATP-dependent nucleosome remodeling molecular motor proteins. Mutations of the human ATRX gene result in a severe genetic disorder termed X-linked α-thalassemia mental retardation (ATR-X) syndrome. Here we perform biochemical and genetic analyses of the Drosophila melanogaster ortholog of ATRX. The loss of function allele of the Drosophila ATRX/XNP gene is semilethal. Drosophila ATRX is expressed throughout development in two isoforms, p185 and p125. ATRX185 and ATRX125 form distinct multisubunit complexes in fly embryo. The ATRX185 complex comprises p185 and heterochromatin protein HP1a. Consistently, ATRX185 but not ATRX125 is highly concentrated in pericentric beta-heterochromatin of the X chromosome in larval cells. HP1a strongly stimulates biochemical activities of ATRX185 in vitro. Conversely, ATRX185 is required for HP1a deposition in pericentric beta-heterochromatin of the X chromosome. The loss of function allele of the ATRX/XNP gene and mutant allele that does not express p185 are strong suppressors of position effect variegation. These results provide evidence for essential biological functions of Drosophila ATRX in vivo and establish ATRX as a major determinant of pericentric beta-heterochromatin identity.
A modular and efficient hardware architecture for particle swarm optimization algorithm

Particle Swarm Optimization (PSO), a population based optimization algorithm, has recently been attracting the attention of the embedded computing community. It is an efficient tool for many continuous multimodal and multidimensional problem classes. This paper first evaluates the performance of the PSO algorithm on embedded processor platforms with limited computational resources. The results on such platforms demonstrate the lack of sufficient execution speed for real-time applications. Thus, to address the shortcomings of the software PSO we developed a hardware architecture that significantly accelerates its execution performance. Besides improving the execution efficiency, the design is shown to be modular, flexible and reusable for solving different optimization problems. The accelerated execution performance of the proposed architecture is demonstrated on standard mathematical benchmark functions as well as on a real world problem scenario: emission source localization in distributed sensor networks. A parallelization scheme for further speed-up of the hardware PSO is also demonstrated.
Effects of endogenous acetylcholine on spontaneous activity in rat dorsal cochlear nucleus slices

We have examined the contribution of endogenous acetylcholine (ACh) release to the spontaneous firing of both regular (probably fusiform cells) and bursting neurons (probably cartwheel cells) in the dorsal cochlear nucleus (DCN) in rat brainstem slices. The muscarinic antagonists atropine, scopolamine, and tropicamide (1-2 microM) caused substantial decreases of firing rates in a majority of the neurons. Reversible acetylcholinesterase (AChE) inhibitors typically caused large transient increases in firing that decayed more slowly than responses to carbachol. The irreversible AChE inhibitor diisopropyl fluorophosphate (DFP) usually caused a sustained increase, with an initial peak followed by a gradual change to a final level higher than before DFP. Tropicamide caused large decreases in firing after DFP, confirming sustained ACh release. Both neostigmine and DFP applied after AChE inhibition by DFP sometimes elicited a transient response. We conclude that the level of sustained response to DFP is determined by the rate of endogenous ACh release, and that DFP and reversible AChE inhibitors exert an initial transient agonist effect that overlaps the initial effect of acetylcholinesterase inhibition. The slice experiments provide a model for cholinergic mechanisms in vivo, confirm that the release of endogenous ACh increases the firing rates of regular and bursting neurons in superficial DCN, and support the hypothesis that spontaneous firing of DCN neurons is sustained in part by cholinergic inputs.
The winter Arctic Oscillation and the timing of snowmelt in Europe

[1] Observations indicate earlier spring snowmelt in the northern hemisphere. We hypothesize that increased temperatures and decreased precipitation due to a positive trend in the winter Arctic Oscillation (AO) have advanced the date of snowmelt. To test this, we modeled snowmelt using the Simple Biosphere model, Version 2 (SiB2) and the National Centers for Environmental Prediction (NCEP) reanalysis from 1958–2002. The simulated snowmelt dates are consistent with dates derived from National Oceanic and Atmospheric Administration (NOAA) weekly snow charts. The winter AO exerts the strongest influence on the timing of snowmelt in northern Europe, with a weaker influence in eastern Siberia and almost no influence in North America. The winter AO trend can statistically explain 20–70% of simulated snowmelt trends in northern Europe.
The effects of fiscal contraction on innovation in the public sector

Beginning in the mid-1970s, fiscal limitation laws, shrinking revenue bases in older cities, and reductions in state and federal grants all have reduced the resources available to carry out the functions of local government. What do these changes portend for the amount of innovation in local government, the types of innovations that are introduced, and the processes of introduction? This paper examines these questions by reviewing the literature on factors related to innovation in public service agencies and reorienting its implications in the new fiscal environment. We conclude that on the whole the innovative process in the public sector has fallen on hard times. Yet, we identify those factors that a creative, innovative administrator can use to advantage in a period of fiscal constraints to bring about innovation. We also identify types of innovations that are likely to succeed.
Fermi-Gamow-Teller Mixing in the Allowed Isospin-Hindered Positron Decay of Co 56

A new high-precision measurement of the asymmetry coefficient, ${A}_{\ensuremath{\beta}}$, for the positron decay of polarized $^{56}\mathrm{Co}$ is reported: ${A}_{\ensuremath{\beta}}=+0.359\ifmmode\pm\else\textpm\fi{}0.009$. If one assumes the $V\ensuremath{-}A$ form of the weak interaction and time-reversal invariance, the Fermi-Gamow-Teller mixing ratio, $y=\frac{{C}_{V}{M}_{F}}{{C}_{A}{M}_{\mathrm{GT}}}$, is then -0.091\ifmmode\pm\else\textpm\fi{}0.005. Since $y$ is nonzero and isospin is not conserved, $^{56}\mathrm{Co}$ ${\ensuremath{\beta}}^{+}$ decay is a good candidate for sensitive time-reversal invariance tests of the weak interaction.