julilili42/papers huggingface dataset:
Chemical freeze-out parameters at RHIC from microscopic model calculations
2001-04-06

The relaxation of hot nuclear matter to an equilibrated state in the central zone of heavy-ion collisions at energies from AGS to RHIC is studied within the microscopic UrQMD model. It is found that the system reaches the (quasi)equilibrium stage for the period of 10-15 fm/ . Within this time the matter in the cell expands nearly isentropically with the entropy to baryon ratio . Thermodynamic characteristics of the system at AGS and at SPS energies at the endpoints of this stage are very close to the parameters of chemical and thermal freeze-out extracted from the thermal fit to experimental data. Predictions are made for the full RHIC energy AGeV. The formation of a resonance-rich state at RHIC energies is discussed.
Electronic effects in scanning tunneling microscopy of dendritic, Cr-filled carbon nanotubes
2001-04-06

We have used ultrahigh vacuum scanning tunneling microscopy (STM) to investigate Cr-filled multiwalled carbon nanotubes. Dendritic and bamboo features were observed in this material. Anomalous contrast effects, resulting in extreme width-to-height ratios, are ascribed to tip effects as well as to intrinsic electronic properties of the filled tubes. In particular, we find that strong apparent height variations along the tube axis are sensitively dependent on the imaging bias. These results suggest that Cr filling of carbon nanotubes results in strong electronic interactions between tube and filling materials.
Simvastatin strongly reduces levels of Alzheimer's disease β-amyloid peptides Aβ42 and Aβ40 in vitro and in vivo
2001-04-10

Recent epidemiological studies show a strong reduction in the incidence of Alzheimer's disease in patients treated with cholesterol-lowering statins. Moreover, elevated Aβ42 levels and the ɛ4 allele of the lipid-carrier apolipoprotein E are regarded as risk factors for sporadic and familial Alzheimer's disease. Here we demonstrate that the widely used cholesterol-lowering drugs simvastatin and lovastatin reduce intracellular and extracellular levels of Aβ42 and Aβ40 peptides in primary cultures of hippocampal neurons and mixed cortical neurons. Likewise, guinea pigs treated with high doses of simvastatin showed a strong and reversible reduction of cerebral Aβ42 and Aβ40 levels in the cerebrospinal fluid and brain homogenate. These results suggest that lipids are playing an important role in the development of Alzheimer's disease. Lowered levels of Aβ42 may provide the mechanism for the observed reduced incidence of dementia in statin-treated patients and may open up avenues for therapeutic interventions.
Substantial stream-disc overflow found in three-dimensional SPH simulations of cataclysmic variables
2001-04-11

We study numerically the interaction of the infalling gas stream and the rim of the accretion disc in cataclysmic variables. The simulations were performed with a smoothed particle hydrodynamics scheme with high spatial resolution. Parameters of the systems AM CVn, OY Car, DQ Her, U Gem and IP Peg were used for the simulations. The simulations cover a wide range of orbital periods, mass ratios and mass transfer rates, as well as different thermal states of the accretion disc. The main result of this study is that the accretion stream is not stopped at the impact region (the bright spot at the outer rim of the disc). In fact, after undergoing the shock interaction, most of the matter is deflected vertically and flows in a more or less diffuse stream to inner parts of the disc, hitting the disc surface close to the circularization radius at orbital phase 0.5. This is a common feature in all systems for all simulated parameters. This stream overflow can cause the X-ray absorption dips observed in cataclysmic variables (CVs) and low-mass X-ray binaries (LMXBs) around orbital phase 0.7, if the inclination is at least 65 degrees. Under certain circumstances, namely a sudden increase of the mass transfer rate from the secondary or a rather small disc, parts of the overflowing stream bounce off the disc surface after hitting it at orbital phase approximate to0.5. Another absorption region can be expected around orbital phase 0.2. In our simulations most of the infalling matter reaches the inner disc very quickly. This must alter the evolution of the quiescent disc and the outburst behaviour considerably compared with purely Viscous transport of the material through the disc from the outer rim, and therefore should be taken into account in dwarf nova outburst cycle calculations. To our knowledge, the consequences of such a massive stream overflow for the dwarf nova outburst cycle have not been considered yet.
Comparative study of the acute nephrotoxicity from standard dose cisplatin +/- ifosfamide and high-dose chemotherapy with carboplatin and ifosfamide.
2001-04-12

The nephrotoxic effects of different platinum compounds based combination chemotherapies were compared. Chemotherapy consisted of either cisplatin fractionated over 5 days (5 x 20 mg/m2) or given as a single-day infusion (1 x 50 mg/m2) plus ifosfamide (4 g/m2) or high-dose chemotherapy was applied including carboplatin (3 x 500 mg/m2) and ifosfamide (3 x 4 g/m2) fractionated over three consecutive days. Conventional parameters such as serum creatinine and glomerular filtration rate (GFR), as well as urinary protein excretion of N-acetyl-beta-D-glucosaminidase (NAG)) and alpha 1-micro-globulin were assessed in 52 patients. Fractionation over 5 days without adding other nephrotoxic agents, i.e. ifosfamide, prevented decreases in GFR following cisplatin, whereas the combination of conventional dose cisplatin and ifosfamide, given as a single-day infusion, and high-dose carboplatin/ifosfamide yielded a pronounced fall of GFR. All groups showed increases in the urinary excretion levels of serum derived proteins and NAG, but with significant differences; about 2 to 3-fold for 5-days cisplatin, 3 to 5-fold for single-day cisplatin/ifosfamide, and 20 to 35-fold for high-dose chemotherapy. Thus, conventional approaches can reduce but not prevent the nephrotoxicity of cisplatin-based chemotherapy. In particular, high-dose chemotherapy regimens including carboplatin and ifosfamide are associated with comparable or even higher nephrotoxicity to single-day cisplatin/ifosfamide. In the light of the long-term consequences of persistent renal damage prevention of nephrotoxicity should be further improved.
Telomerase activity in long-standing ulcerative colitis.
2001-04-12

Telomerase activity is frequently associated with neoplasia. It is a ribonucleoprotein capable of replacing telomeric DNA sequences that are lost at each cell division. Neoplastic progression in chronic ulcerative colitis is characterized by the development of epithelial dysplasia which is accompanied by genetic alterations. Therefore we tested telomerase activity in 128 biopsy samples of four colectomy specimens with long-standing ulcerative pancolitis by using the Telomerase PCR ELISA System. In three patients with multiple dysplastic or carcinomatous lesions, telomerase activity was detected in 22 samples with a regional association to dysplastic or carcinomatous areas. 15 of the samples with telomerase activity (68%) were found in dysplastic/carcinomatous samples or in the direct vicinity of dysplastic areas, 4 (18%), 2 positions (about 4 cm) and the remaining three (14%) not more than 3 positions away from such areas. In the fourth patient, resected because of clinical deterioration despite medical treatment and who had no dysplastic lesions, no telomerase activity was detected. These results show that telomerase activity might be used as a complementary marker to histology for the identification of patients with ulcerative colitis who are at an increased risk for neoplastic progression.
N-cadherin is developmentally regulated and functionally involved in early hematopoietic cell differentiation
2001-04-15

ABSTRACT The cadherins, an important family of cell adhesion molecules, are known to play major roles during embryonic development and in the maintenance of solid tissue architecture. In the hematopoietic system, however, little is known of the role of this cell adhesion family. By RT-PCR, western blot analysis and immunofluorescence staining we show that N-cadherin, a classical type I cadherin mainly expressed on neuronal, endothelial and muscle cells, is expressed on the cell surface of resident bone marrow stromal cells. FACS analysis of bone marrow mononuclear cells revealed that N-cadherin is also expressed on a subpopulation of early hematopoietic progenitor cells. Triple-color FACS analysis defined a new CD34+ CD19+ N-cadherin+ progenitor cell population. During further differentiation, however, N-cadherin expression is lost. Treatment of CD34+ progenitor cells with function-perturbing N-cadherin antibodies drastically diminished colony formation, indicating a direct involvement of N-cadherin in the differentiation program of early hematopoietic progenitors. N-cadherin can also mediate adhesive interactions within the bone marrow as demonstrated by inhibition of homotypic interactions of bone-marrow-derived cells with N-cadherin antibodies. Together, these data strongly suggest that N-cadherin is involved in the development and retention of early hematopoietic progenitors within the bone marrow microenvironment.
Cutting Edge: Characterization of Allorestricted and Peptide-Selective Alloreactive T Cells Using HLA-Tetramer Selection
2001-04-15

Abstract The vast majority of alloreactive T cells recognize foreign MHC molecules in a peptide-dependent manner. A subpopulation of these peptide-dependent alloreactive T cells is peptide-specific and contains T cells that are of interest for tumor immunotherapy. Allorestricted T cells (i.e., peptide-specific and alloreactive) specific for tumor-associated Ags can be raised in vitro. However, it is technically difficult to distinguish between peptide-specific and peptide-nonspecific alloreactive T cells by functional assays in vitro. Here we show for the first time that allorestricted T cells specifically bind HLA-peptide tetrameric complexes, as nominal Ag-specific T cells would do. In consequence, fluorescent HLA-peptide tetrameric complexes can be used for sorting and cloning of allorestricted CTLs specific for a peptide of interest. We also show by the mean of HLA-peptide tetramers the existence of peptide-selective alloreactive T cells that recognize a conformation on the foreign-MHC brought about by some but not all peptides bound.
Nonafluorobutanesulfonyl Fluoride
2001-04-15

[375-72-4] C4F10O2S (MW 302.11) InChI = 1S/C4F10O2S/c5-1(6,3(9,10)11)2(7,8)4(12,13)17(14,15)16 InChIKey = LUYQYZLEHLTPBH-UHFFFAOYSA-N (mild alkylating reagent for amines and alkoxysilanes; precursor for nonafluorobutanesulfinic and -sulfonic acids and various nonafluorobutyl sulfones) Alternate Name: NfF. Physical Data: bp 65–66 °C/760 mmHg; d 1.682 g cm−3. Solubility: sol ether, THF; insol CH2Cl2. Form Supplied in: colorless to pale yellow liquid of 90% purity; impurities are branched nonafluorobutanesulfonyl fluorides. Analysis of Reagent Purity: 19F NMR;1 MS.2 Preparative Methods: by electrochemical fluorination of alkanesulfonyl halides in anhyd HF at 4–6 V,3 or, better, by electrochemical fluorination of sulfolene.1 Purification: dried over CaCl2 and distilled. Handling, Storage, and Precautions: store in amber colored bottles protected from light; for prolonged storage, PVC bottles are recommended.
Methanesulfonic Acid
2001-04-15

[75-75-2] CH4O3S (MW 96.12) (cyclocondensation reagent; precursor for methanesulfonyl chloride and anhydride; catalyst for polymerization, alkylation, and esterification reactions) Alternate Name: MsOH. Physical Data: mp 20 °C; bp 167 °C/10 mmHg, 122 °C/1 mmHg; d 1.481 g cm−3; nD20 1.3210. Solubility: sol water, ethanol, ether; insol hexane; very sparingly sol benzene, toluene. Form Supplied in: technical quality is 95% pure containing 2% water. Analysis of Reagent Purity: 17O NMR.1 Preparative Method: by oxidation of Dimethyl Sulfide with Dimethyl Sulfoxide in the presence of water and a catalytic amount of Hydrogen Bromide.17 Purification: stir with P2O5 (20 g for 500 mL of the acid) at 100 °C for 0.5 h and then distill under vacuum. Handling, Storage, and Precautions: irritant and highly corrosive liquid; should be stored in glass containers. Use in a fume hood.
Trifluoromethanesulfonic Acid
2001-04-15

[1493-13-6] CHF3O3S (MW 150.09) (one of the strongest organic acids; catalyst for oligomerization/polymerization of alkenes and ethers; precursor for triflic anhydride and several metal triflates; acid catalyst in various reactions) Alternate Name: triflic acid. Physical Data: bp 162 °C/760 mmHg, 84 °C/43 mmHg, 54 °C/8 mmHg; d 1.696 g cm−3. Solubility: sol water and in many polar organic solvents such as DMF, sulfolane, DMSO, dimethyl sulfone, acetonitrile; sol alcohols, ketones, ethers, and esters, but these generally are not suitable inert solvents (see below). Analysis of Reagent Purity: IR;2 19F NMR.4 Preparative Methods: best prepared by basic hydrolysis of CF3SO2F followed by acidification.2 Purification: distilled with a small amount of Tf2O.6 Handling, Storage, and Precautions: is a stable, hygroscopic liquid which fumes copiously on exposure to moist air. Transfer under dry nitrogen is recommended. Contact with cork, rubber, and plasticized materials will cause rapid discoloration of the acid and deterioration of the materials. Samples are best stored in sealed glass ampules or glass bottles with Kel-FTM or PTFE plastic screw cap linings. Use in a fume hood.
Propylene Oxide
2001-04-15

[75-56-9] C3H6O (MW 58.09) (monomer for polymerization; electrophile; chiral building block) Alternate Names: 1,2-epoxypropane; methyloxirane. Physical Data: mp −112 °C; bp 34 °C; d 0.859 g cm−3; [α]D20 +14.6° for the (R)-enantiomer, corrected to 100% ee. Solubility: sol H2O (405 g L−1); miscible with organic solvents. Form Supplied in: colorless liquid; commercially available as a racemic mixture and as the enantiomers. Drying: distillation from calcium hydride or calcium. Upon cooling, a hydrate C3H6O·(H2O)16 of mp −3 °C is precipitated from the moist oxirane as white crystals.2 Analysis of Reagent Purity: 13C NMR (CDCl3): δ 47.1, 46.8 (C-1, C-2), 17.2 (C-3) ppm; determination of ee by complexation gas chromatography on nickel(II) bis[3-heptafluorobutanoyl-(1R)-camphorate] in squalane, separation factor α 1.24 at 50 °C;3 other suitable chiral stationary phases are nickel(II) bis[2-heptafluorobutanoyl-(S)-4-methylthujan-3-onate] and manganese(II) bis[3-heptafluorobutanoyl-(1R)-camphorate].4 Preparative Methods: (R)-propylene oxide is prepared (eq 1) in three steps: diazotization of (S)-alanine with Sodium Nitrite in hydrochloric acid; to give (S)-2-chloropropanoic acid; reduction to 2-chloropropan-1-ol with Lithium Aluminum Hydride; and cyclization by distillation from Potassium Hydroxide pellets.4, 5 (1) The (S)-enantiomer is prepared from (S)‐Ethyl Lactate via (S)-propane-1,2-diol, and cyclization of a mixture of (S)-2-acetoxy-1-bromopropane and (R)-2-bromo-1-acetoxypropane (eq 2).6, 7 (2) Alternatively, conversion of (S)-ethyl lactate into the mesylate is followed by reduction of the ester group with Aluminum Hydride/THF and ring closure with aqueous KOH.8 Another route to (S)-propylene oxide involves protection of the (secondary) hydroxyl group of (S)-ethyl lactate with Ethyl Vinyl Ether, followed by reduction of the ester group with LiAlH4, conversion of the primary hydroxyl group into the tosylate, acidic deprotection of the secondary hydroxyl group, and cyclization with aqueous KOH.9 By means of a combined microbial/chemical synthesis, (R)-propylene oxide is obtained from glucose with ee >99%.10 Metal-mediated access to both enantiomers is provided by either chromatographic or kinetic resolution of racemic propylene oxide, and also by asymmetric epoxidation of propylene.11 Handling, Storage, and Precautions: a suspected carcinogen for humans; it is inflammable and explosive; because of its high volatility, cooling to 0 °C before use is recommended. Use in a fume hood.
Sensorimotor mapping of the human cerebellum: fMRI evidence of somatotopic organization
2001-04-17

Abstract Functional magnetic resonance imaging (fMRI) was employed to determine areas of activation in the cerebellar cortex in 46 human subjects during a series of motor tasks. To reduce the variance due to differences in individual anatomy, a specific transformational procedure for the cerebellum was introduced. The activation areas for movements of lips, tongue, hands, and feet were determined and found to be sharply confined to lobules and sublobules and their sagittal zones in the rostral and caudal spino‐cerebellar cortex. There was a clear symmetry mirroring at the midline. The activation mapped as two distinct homunculoid representations. One, a more extended representation, was located upside down in the superior cerebellum, and a second one, doubled and smaller, in the inferior cerebellum. The two representations were remarkably similar to those proposed by Snider and Eldred [ 1951 ] five decades ago. In the upper representation, an intralimb somatotopy for the right elbow, wrist, and fingers was revealed. The maps seem to confirm earlier electrophysiological findings of sagittal zones in animals. They differ, however, from micromapping reports on fractured somatotopic maps in the cerebellar cortex of mammals. We assume that the representations that we observed are not solely the result of spatial integration of hemodynamic events underlying the fMRI method and may reflect integration of afferent peripheral and central information in the cerebellar cortex. Hum. Brain Mapping 13:55–73, 2001. © 2001 Wiley‐Liss, Inc.
Oxoammonium Resins as Metal-Free, Highly Reactive, Versatile Polymeric Oxidation Reagents
2001-04-17

Polymer-supported oxidation of alcohols was conducted very efficiently by employing oxoammonium salts, the reactive intermediates in TEMPO oxidations (TEMPO=2,2,6,6-tetramethylpiperidinoxyl). These highly reactive salts (see scheme; X=Br, Cl) could be prepared and isolated on the polymeric support, and were used for the conversion of single compounds as well as of complex mixtures of alcohols.
Influence of flap design on peri-implant interproximal crestal bone loss around single-tooth implants.
2001-04-19

The anterior maxilla represents a therapeutic challenge for single-tooth replacement with implants. The surgical trauma delivered to soft and hard tissues during implant placement can influence the future esthetic result. The clinician should use surgical techniques that prevent esthetic complications, such as increased crown length or loss of interdental papillae, without compromising osseointegration. This prospective study investigated the interproximal crestal bone loss occurring after placement of single-tooth implants using 2 different flap designs: a widely mobilized flap design that included papillae, and a limited flap design that protected papillae. The interproximal crestal bone loss was of practical importance and statistically significantly less following the use of a limited flap design versus the widely mobilized flap procedure.
Protein Determination
2001-04-19

Abstract Protein determination aims at estimating the concentration of protein in unknown samples by comparing the unknown sample with a known standard. Sample preparation and choice of a suitable standard are the most important criteria for the accuracy of the results.
Shoots and Buds
2001-04-19

Abstract The shoot of higher plants carries the branches, foliage and flowers. Repetitive organ formation takes place at the tip of shoots and in floral buds by the activity of stem cell systems, the shoot and flower meristems.
Trichomes
2001-04-19

Abstract A ‘trichome’ (or hair) is an outgrowth derived from the shoot or root epidermis of a plant. The form and distribution of trichomes differs between plant species or genera, but recent molecular work reveals that there are common regulatory pathways for trichome development of different types within the same plant species and possibly also across plant species.
MR‐guided biopsy of musculoskeletal lesions in a low‐field system
2001-04-23

Abstract Thirty magnetic resonance (MR)‐guided biopsies were obtained from 20 skeletal and 10 soft‐tissue lesions in 31 patients using an open 0.2 T MR system equipped with interventional accessories. The results from aspiration ( N = 3), core biopsy ( N = 15), and transcortical trephine biopsy ( N = 12) were evaluated for accuracy and clinical efficacy. Specimens were successfully obtained from 29 patients. Results were clinically effective in 23 patients, rated definitive in 16, nonconclusive in 9, and unspecific in 2 patients. A false diagnosis due to sampling error occurred in 2 patients, and biopsy sampling was impossible in one case. The best diagnostic yield was achieved from nontranscortical biopsies of osteolytic or soft‐tissue masses. Results from transcortical biopsies were less specific due to the predominance of benign lesions. MR fluoroscopy for needle guidance was applied in 13 patients. Complete needle placement inside the magnet could be performed in 16 patients. MR‐guided biopsy using an open low‐field MR imager is feasible and clinically effective and will become a valuable tool in the management of musculoskeletal lesions. J. Magn. Reson. Imaging 2001;13:761–768. © 2001 Wiley‐Liss, Inc.
Association of 4F2hc with light chains LAT1, LAT2 or y+LAT2 requires different domains
2001-04-24

Heterodimeric amino acid transporters are comprised of a type-II membrane protein named the heavy chain (4F2hc or rBAT) that may associate with a number of different polytopic membrane proteins, called light chains. It is thought that the heavy chain is mainly involved in the trafficking of the complex to the plasma membrane, whereas the transport process itself is catalysed by the light chain. The 4F2heavy chain (4F2hc) associates with at least six different light chains to induce distinct amino acid-transport activites. To test if the light chains are specifically recognized and to identify domains involved in the recognition of light chains, C-terminally truncated mutants of 4F2hc were constructed and co-expressed with the light chains LAT1, LAT2 and y+LAT2. The truncated isoform T1, comprised of only 133 amino acids that form the cytosolic N-terminus and the transmembrane helix, displayed only a slight reduction in its ability to promote LAT1 expression at the membrane surface compared with the 529 amino acid wild-type 4F2hc protein. Co-expression of increasingly larger 4F2hc mutants caused a delayed translocation of LAT1. In contrast to the weak effects of 4F2hc truncations on LAT1 expression, surface expression of LAT2 and y+LAT2 was almost completely lost with all truncated heavy chains. Co-expression of LAT1 together with the other light chains did not result in displacement of LAT2 and y+LAT2. The results suggest that extracellular domains of the heavy chain are responsible mainly for recognition of light chains other than LAT1 and that the extracellular domain ensures proper translocation to the plasma membrane.
History of Ecology
2001-04-25

Abstract Although there have been ‘ecological’ ideas and investigations over many centuries, the history of ecology as a self‐conscious science started only in the last decades of the nineteenth century. A description of the development of ecology since then shows both the plurality of approaches and subjects and the desire to arrive at unifying theories.
Plant Tissues
2001-04-25

Abstract Higher plants are organized into three tissue layers: the epidermis, the ground tissue and the vascular system. The separation of the three layers is established in the meristems and they are largely maintained as separate tissues, reflecting their separate cell lineages.