The Determination of the Dielectric Constants of Aqueous Salt Solutions at Ultra High Frequencies

The determination of the dielectric constants of aqueous salt solutions is accomplished by an adaptation of the method used by Paul Drude in 1897. A stable ultra high frequency vacuum tube oscillator is used to produce standing waves in an inductively coupled Lecher wire system. The wave length used is 123 cm. The resonant point on the parallel wires, crossed by a condenser containing the salt solution, is used to measure the dielectric constant. The results obtained with KCl and K2SO4 solutions indicate that interesting and reliable results may be expected even for good conductors

Semi-Micro Analysis of Tungsten

The growing use of tungsten in high speed steels and for electrical purposes makes it increasingly desirable to include this element in the scheme of analysis. Metallic tungsten is seldom if ever found in nature, but occurs in several well-crystallized tungsten minerals of which Scheelite, CaW04 , is typical. From its position in the periodic table, Group VI - Series 6, one should expect tungsten to have amphoteric properties. Although we are more familiar with tungsten in the metallic state, it almost invariably behaves as a non-metal in chemical combination. For this reason in analytical work tungsten naturally falls among the anions

Some Observations of the Boiling Point of Ternary Liquid Mixtures

An exposition of an apparatus for the determination of the boiling points of liquid mixtures under constant pressure, and the results of preliminary investigations upon ternary mixtures of some common organic liquids

The Determination of Surface Tension by Standing Waves

The velocity with which a wave travels over the surface of a liquid depends upon the surface tension of the liquid as well as on a gravity force due to the displacement of the liquid from its undisturbed position. For waves of large wavelength the effect of surface tension on the velocity of the wave is small; however for small wavelengths the gravity force is very small and the velocity of the wave is determined almost entirely by the surface tension. We shall therefore consider waves of very small wavelength

The Use of Electron Tubes as Super-Sensitive Relays

A brief discussion of the use of electron tubes in relay circuits controlling physical apparatus. The construction and operation of several relay units were shown

The Construction and Use of a Concave Grating Spectrograph

In order to learn some of the fundamentals of analytical spectrography, a concave grating spectrograph was constructed as a cooperative student-faculty project. Details of construction and methods of use were given. Both qualitative and quantitative applications of the instrument are considered

Manual versus automatic bladder wall thickness measurements: a method comparison study

Purpose To compare repeatability and agreement of conventional ultrasound bladder wall thickness (BWT) measurements with automatically obtained BWT measurements by the BVM 6500 device. Methods Adult patients with lower urinary tract symptoms, urinary incontinence, or postvoid residual urine were urodynamically assessed. During two subsequent cystometry sessions the infusion pump was temporarily stopped at 150 and 250 ml bladder filling to measure BWT with conventional ultrasound and the BVM 6500 device. For each method and each bladder filling, repeatability and variation was assessed by the method of Bland and Altman. Results Fifty unselected patients (30 men, 20 women) aged 21–86 years (median 62.5 years) were prospectively evaluated. Invalid BWT measurements were encountered in 2.1–14% of patients when using the BVM 6500 versus 0% with conventional ultrasound (significant only during the second measurement at 150 ml bladder filling). Mean difference in BWT values between the measurements of one technique was -0.1 to +0.01 mm. Measurement variation between replicate measurements was smaller for conventional ultrasound and the smallest for 250 ml bladder filling. Mean difference between the two techniques was 0.11–0.23 mm and did not differ significantly. The BVM 6500 device was not able to correctly measure BWTs above 4 mm. Conclusions Both BWT measurements are repeatable and agree with each other. However, conventional ultrasound measurements have a smaller measurement variance, can measure BWT in all patients, and BWTs above 4 mm

Catalytic Enantioselective Cross-Couplings of Secondary Alkyl Electrophiles with Secondary Alkylmetal Nucleophiles: Negishi Reactions of Racemic Benzylic Bromides with Achiral Alkylzinc Reagents

We have developed a nickel-catalyzed method for the asymmetric cross-coupling of secondary electrophiles with secondary nucleophiles, specifically, stereoconvergent Negishi reactions of racemic benzylic bromides with achiral cycloalkylzinc reagents. In contrast to most previous studies of enantioselective Negishi cross-couplings, tridentate pybox ligands are ineffective in this process; however, a new, readily available bidentate isoquinoline–oxazoline ligand furnishes excellent ee’s and good yields. The use of acyclic alkylzinc reagents as coupling partners led to the discovery of a highly unusual isomerization that generates a significant quantity of a branched cross-coupling product from an unbranched nucleophile

Humoral and Cellular CMV Responses in Healthy Donors; Identification of a Frequent Population of CMV-Specific, CD4+ T Cells in Seronegative Donors

CMV status is an important risk factor in immune compromised patients. In hematopoeitic cell transplantations (HCT), both donor and recipient are tested routinely for CMV status by serological assays; however, one might argue that it might also be of relevance to examine CMV status by cellular (i.e., T lymphocyte) assays. Here, we have analyzed the CMV status of 100 healthy blood bank donors using both serology and cellular assays. About half (56%) were found to be CMV seropositive, and they all mounted strong CD8+ and/or moderate CD4+ T cell responses ex vivo against the immunodominant CMV protein, pp65. Of the 44 seronegative donors, only five (11%) mounted ex vivo T cell responses; surprisingly, 33 (75%) mounted strong CD4+ T cell responses after a brief in vitro peptide stimulation culture. This may have significant implications for the analysis and selection of HCT donors