Optical control of internal electric fields in band gap-graded InGaN nanowires

InGaN nanowires are suitable building blocks for many future optoelectronic devices. We show that a linear grading of the indium content along the nanowire axis from GaN to InN introduces an internal electric field evoking a photocurrent. Consistent with quantitative band structure simulations we observe a sign change in the measured photocurrent as a function of photon flux. This negative differential photocurrent opens the path to a new type of nanowire-based photodetector. We demonstrate that the photocurrent response of the nanowires is as fast as 1.5 ps.

Giant spin Seebeck effect in a non-magnetic material

The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ∼25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values.

Spin-seebeck effect: a phonon driven spin distribution

Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution.

Observation of the spin-Seebeck effect in a ferromagnetic semiconductor

Reducing the heat generated in traditional electronics is a chief motivation for the development of spin-based electronics, called spintronics. Spin-based transistors that do not strictly rely on the raising or lowering of electrostatic barriers can overcome scaling limits in charge-based transistors. Spin transport in semiconductors might also lead to dissipation-less information transfer with pure spin currents. Despite these thermodynamic advantages, little experimental literature exists on the thermal aspects of spin transport in solids. A recent and surprising exception was the discovery of the spin-Seebeck effect, reported as a measurement of a redistribution of spins along the length of a sample of permalloy (NiFe) induced by a temperature gradient. This macroscopic spatial distribution of spins is, surprisingly, many orders of magnitude larger than the spin diffusion length, which has generated strong interest in the thermal aspects of spin transport. Here, the spin-Seebeck effect is observed in a ferromagnetic semiconductor, GaMnAs, which allows flexible design of the magnetization directions, a larger spin polarization, and measurements across the magnetic phase transition. This effect is observed even in the absence of longitudinal charge transport. The spatial distribution of spin currents is maintained across electrical breaks, highlighting the local nature of this thermally driven effect.

A Net Sink for Atmospheric CH3Br in the East Pacific Ocean

Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH(3)Br) in most areas except for coastal and upwelling regions, with saturation anomalies ranging from + 100 percent in coastal waters to -50 percent in open ocean areas, representing a regionally weighted mean of -16 (-13 to -20) percent. The partial lifetime of atmospheric CH(3)Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH3Br in the atmosphere was 9.8 +/- 0.6 parts per trillion, with an interhemispheric ratio of 1.31 +/- 0.08. These data indicate that approximately 8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH3Br could be attributed to an uneven global distribution of oceanic sources and sinks.

Zero-field optical manipulation of magnetic ions in semiconductors

Controlling and monitoring individual spins is desirable for building spin-based devices, as well as implementing quantum information processing schemes. As with trapped ions in cold gases, magnetic ions trapped on a semiconductor lattice have uniform properties and relatively long spin lifetimes. Furthermore, diluted magnetic moments in semiconductors can be strongly coupled to the surrounding host, permitting optical or electrical spin manipulation. Here we describe the zero-field optical manipulation of a few hundred manganese ions in a single gallium arsenide quantum well. Optically created mobile electron spins dynamically generate an energy splitting of the ion spins and enable magnetic moment orientation solely by changing either photon helicity or energy. These polarized manganese spins precess in a transverse field, enabling measurements of the spin lifetimes. As the magnetic ion concentration is reduced and the manganese spin lifetime increases, coherent optical control and readout of single manganese spins in gallium arsenide should be possible.

Onset of Ferromagnetism in Low-Doped Ga1-xMnxAs

We develop a quantitatively predictive theory for impurity-band ferromagnetism in the low-doping regime of Ga1-xMnxAs. We compare it with measurements of a series of samples whose compositions span the transition from paramagnetic insulating to ferromagnetic conducting behavior. The theoretical Curie temperatures depend sensitively on the local fluctuations in the Mn-hole binding energy, which originate from Mn disorder and As antisite defects. The experimentally determined hopping energy is an excellent predictor of the Curie temperature, in agreement with the theory.

Generating spin currents in semiconductors with the spin Hall effect

We investigate electrically induced spin currents generated by the spin Hall effect in GaAs structures that distinguish edge effects from spin transport. Using Kerr rotation microscopy to image the spin polarization, we demonstrate that the observed spin accumulation is due to a transverse bulk electron spin current, which can drive spin polarization nearly 40 microns into a region in which there is minimal electric field. Using a model that incorporates the effects of spin drift, we determine the transverse spin drift velocity from the magnetic field dependence of the spin polarization.

Suppression of spin relaxation in submicron InGaAs wires

We investigate electron-spin dynamics in narrow two-dimensional n-InGaAs channels as a function of the channel width. The spin relaxation times increase with decreasing channel width, in accordance with recent theoretical predictions based on the dimensionally constrained D'yakonov-Perel' mechanism. Surprisingly, the suppression of the relaxation rate, which is anticipated for the one-dimensional limit, is observed for widths that are an order of magnitude larger than the electron mean free path. We find the spin precession length and the channel width to be the relevant length scales for interpreting these results.

Enhancement of spin coherence using Q-factor engineering in semiconductor microdisc lasers

Semiconductor microcavities offer unique means of controlling light-matter interactions in confined geometries, resulting in a wide range of applications in optical communications and inspiring proposals for quantum information processing and computational schemes. Studies of spin dynamics in microcavities, a new and promising research field, have revealed effects such as polarization beats, stimulated spin scattering and giant Faraday rotation. Here, we study the electron spin dynamics in optically pumped GaAs microdisc lasers with quantum wells and interface-fluctuation quantum dots in the active region. In particular, we examine how the electron spin dynamics are modified by the stimulated emission in the discs, and observe an enhancement of the spin-coherence time when the optical excitation is in resonance with a high-quality (Q approximately 5,000) lasing mode. This resonant enhancement, contrary to expectations from the observed trend in the carrier-recombination time, is then manipulated by altering the cavity design and dimensions. In analogy with devices based on excitonic coherence, this ability to engineer coherent interactions between electron spins and photons may provide new pathways towards spin-dependent quantum optoelectronics.

Antiferromagnetic s-d exchange coupling in GaMnAs

Measurements of coherent electron spin dynamics in Ga1-xMnxAs/Al0.4Ga0.6As quantum wells with 0.0006%<x<0.03% show an antiferromagnetic (negative) exchange between s-like conduction band electrons and electrons localized in the d shell of the Mn2+ impurities. The magnitude of the s-d exchange parameter, N0alpha, varies as a function of well width indicative of a large and negative contribution due to kinetic exchange. In the limit of no quantum confinement, N0alpha extrapolates to -0.09+/-0.03 eV indicating that antiferromagnetic s-d exchange is a bulk property of GaMnAs. Measurements of the polarization-resolved photoluminescence show strong discrepancy from a simple model of the exchange enhanced Zeeman splitting, indicative of additional complexity in the exchange split valence band.

Observation of the spin Hall effect in semiconductors

Electrically induced electron-spin polarization near the edges of a semiconductor channel was detected and imaged with the use of Kerr rotation microscopy. The polarization is out-of-plane and has opposite sign for the two edges, consistent with the predictions of the spin Hall effect. Measurements of unstrained gallium arsenide and strained indium gallium arsenide samples reveal that strain modifies spin accumulation at zero magnetic field. A weak dependence on crystal orientation for the strained samples suggests that the mechanism is the extrinsic spin Hall effect.

Current-induced spin polarization in strained semiconductors

The polarization of conduction electron spins due to an electrical current is observed in strained nonmagnetic semiconductors using static and time-resolved Faraday rotation. The density, lifetime, and orientation rate of the electrically polarized spins are characterized by a combination of optical and electrical methods. In addition, the dynamics of the current-induced spins are investigated by utilizing electrical pulses generated from a photoconductive switch. These results demonstrate the possibility of a spin source for semiconductor spintronic devices without the use of magnetic materials.

Coherent spin manipulation without magnetic fields in strained semiconductors

A consequence of relativity is that in the presence of an electric field, the spin and momentum states of an electron can be coupled; this is known as spin-orbit coupling. Such an interaction opens a pathway to the manipulation of electron spins within non-magnetic semiconductors, in the absence of applied magnetic fields. This interaction has implications for spin-based quantum information processing and spintronics, forming the basis of various device proposals. For example, the concept of spin field-effect transistors is based on spin precession due to the spin-orbit coupling. Most studies, however, focus on non-spin-selective electrical measurements in quantum structures. Here we report the direct measurement of coherent electron spin precession in zero magnetic field as the electrons drift in response to an applied electric field. We use ultrafast optical techniques to spatiotemporally resolve spin dynamics in strained gallium arsenide and indium gallium arsenide epitaxial layers. Unexpectedly, we observe spin splitting in these simple structures arising from strain in the semiconductor films. The observed effect provides a flexible approach for enabling electrical control over electron spins using strain engineering. Moreover, we exploit this strain-induced field to electrically drive spin resonance with Rabi frequencies of up to approximately 30 MHz.

Local manipulation of nuclear spin in a semiconductor quantum well

The shaping of nuclear spin polarization profiles and the induction of nuclear resonances are demonstrated within a parabolic quantum well using an externally applied gate voltage. Voltage control of the electron and hole wave functions results in nanometer-scale sheets of polarized nuclei positioned along the growth direction of the well. Applying rf voltages across the gates induces resonant spin transitions of selected isotopes. This depolarizing effect depends strongly on the separation of electrons and holes, suggesting that a highly localized mechanism accounts for the observed behavior.

Difficulties associated with the development and licensing of vaccines for protection against bio-warfare and bio-terrorism

Today there is an increasing need to license vaccines for the protection of individuals against bio-warfare and bio-terrorism. While the need is apparent, the actual road to developing, producing and licensing such vaccines successfully is as yet undefined. Bio-defence vaccine candidates may come from several sources. They may come from vaccines that were previously licensed but are no longer in production, vaccines that are currently in an IND status, vaccines currently licensed in foreign countries, and newer vaccines currently under development. The issues that apply to the development and licensing of these vaccines can be defined by currently accepted standards for manufacture, and the requirement to demonstrate safety and efficacy to a level that gives the scientific and medical community, regulatory agencies, users and the public at large confidence. Requirements for manufacturing and demonstration of safety will be consistent with vaccines being developed for traditional purposes. However, demonstration of efficacy will be more difficult. Because field trials for these vaccines are generally not feasible and the conduct of human challenge studies is generally considered unethical, the demonstration of efficacy will need to be based on existing efficacy data, a thorough understanding of both the disease's pathogenesis and mechanism of protection, the ability to identify surrogate markers for efficacy, and the use of the proposed FDA "animal rule".

Gigahertz electron spin manipulation using voltage-controlled g-tensor modulation

We present a scheme that enables gigahertz-bandwidth three-dimensional control of electron spins in a semiconductor heterostructure with the use of a single voltage signal. Microwave modulation of the Landé g tensor produces frequency-modulated electron spin precession. Driving at the Larmor frequency results in g-tensor modulation resonance, which is functionally equivalent to electron spin resonance but without the use of time-dependent magnetic fields. These results provide proof of the concept that quantum spin information can be locally manipulated with the use of high-speed electrical circuits.

The acute toxicity and primary irritancy of glutaraldehyde solutions

Glutaraldehyde (GA, CAS Number 110-30-8), an aliphatic dialdehyde, has a wide range of industrial, scientific, and medical applications. It is available in aqueous solutions, whose concentrations vary up to 50% (w/w) and from which there is a potential during use for skin and eye contact and exposure to the vapor. The acute toxicity and primary irritancy of a wide range of GA concentrations were investigated to determine the differential hazards for such solutions. The acute peroral toxicity in the rat, expressed as ml of solution dosed, was moderate for solutions of 5% and above (LD50 range 0.88-3.25 ml/kg) and generally varied little for solutions up to 50%. Solutions less than 5% GA were of slight toxicity (LD50 range 3.34-12.30 ml/kg for 1 and 2% solutions). When lethality was expressed as absolute amount of GA dosed (mg GA/kg), there was a reciprocal relationship between the concentration of GA solution dosed and LD50. This was confirmed in the mouse, which is more susceptible than the rat to acute peroral toxicity. The acute percutaneous toxicity of GA solutions to rabbits (24 h occlusion) was moderate (LD50 range 1.59-2.71 ml/kg) for 46 and 50% solutions, and slight for 25% GA solutions (8.80-16.00 ml/kg). At 15% and less, 16.0 ml/kg was not lethal. Exposures (4-8 h) of rats to saturated vapor atmospheres of GA generated dynamically or statistically at ambient temperature (17-25 C) produced only transient peripheral sensory irritant effects to the eyes and respiratory tract. In contrast, vapor atmosphere generated dynamically at elevated temperature (60 or 65 C) produce severe effects, including mortality (4-h LC50 range 23.5-44.3 ppm). Histopathology in rats that died included exposure concentration-related acute inflammation and necrosis in the nasal mucosa, larynx, trachea, and bronchi. Standard primary skin irritation tests in the rabbit indicated severe skin irritation and necrosis at 45 and 50% GA; necrosis occurred with 1 and 4 h contact at 50% and at 4 h with 45%. Inflammation was moderate at 25%, slight to moderate with 5 and 10% GA, minor at 2%, and threshold at 1%. Standard primary eye irritation tests showed 45% GA to produce severe conjunctival and corneal injury, which was persistent. At 2% GA corneal injury was mild, and at 5% marked. The lowest concentration producing corneal injury was 1.0%, and the no-effects concentration was 0.5%. The threshold for conjunctival effects was 0.2%, and the no-effects concentration 0.1%. At 1% GA, conjunctival hyperemia and chemosis were moderate to marked, and became more severe with higher GA concentrations. The results suggest potential acute handling hazards with various concentrations of GA solutions and indicate industrial hygiene considerations.

Black holes radiate mainly on the brane

We examine the evaporation of a small black hole on a brane in a world with large extra dimensions. Since the masses of many Kaluza-Klein modes are much smaller than the Hawking temperature of the black hole, it has been claimed that most of the energy is radiated into these modes. We show that this is incorrect. Most of the energy goes into the modes on the brane. This raises the possibility of observing Hawking radiation in future high energy colliders if there are large extra dimensions.

Acute toxicity, primary irritancy, and genetic toxicity studies with 3-(methylthio)propionaldehyde

Basic acute toxicity, primary irritancy, and genetic toxicity studies were conducted with 3-(methylthio)propionaldehyde (3-MTP). The acute rat peroral LD50 (with 95% confidence limits) for 3-MTP as a 25% (v/v) dilution in corn oil was 1.00 (0.59-1.70) ml/kg (males) and 1.68 (0.95-2.99) ml/kg (females); most deaths occurred 1.5 to 4 h postdosing. By 24-h occluded contact with undiluted 3-MTP, the rabbit acute percutaneous LD50 was 0.71 (0.43-1.15) ml/kg (males) and 0.79 (0.49-1.30) ml/kg (females): times to death ranged from 2 h to 2 d after the start of dosing. Exposure of rats to a statically generated saturated atmosphere killed all 5 males with a 40 min exposure and all 5 females with a 24 min exposure. In contrast, a 4-h exposure of rats to a dynamically generated saturated vapor atmosphere of 3-MTP did not produce any mortalities or signs of toxicity. A 4-hr occluded contact with 0.5 ml undiluted 3-MTP caused moderate to severe erythema and severe edema resolving by 7 to 17 d. Five/6 animals had necrosis apparent on removal of the occlusive dressing and persisting 10 to 17 d. On the rabbit eye, 0.1 ml undiluted 3-MTP produced moderate to severe corneal injury with iritis and moderate conjunctival inflammation which persisted 21 d in 3/6 animals; 0.01 ml caused moderate diffuse corneal injury and moderate conjunctival inflammation with healing by 7 d. 3-MTP did not produce mutagenic activity either in the absence or presence of metabolic activation with a Salmonella typhimurium reverse mutation assay using strains TA98, TA100, TA1535, TA1537 and TA1538. In a mouse lymphoma cell (L5178Y/tk +/-) assay, 3-MTP produced concentration-related increases in mutant colonies, both in the absence and presence of metabolic activation. Increases were mainly in the sigma (chromosomal damaging) colonies. In a mouse bone marrow micronucleus study, with vapor exposures to 37.4, 88.5 and 155.6 ppm for 1 h/d for 2 consecutive d, there were exposure concentration-related increases in micronucleated erythrocytes which were statically significant for male mice.

Influence of alkalinization of glutaraldehyde biocidal solutions on acute toxicity, primary irritancy, and skin sensitization

Aqueous glutaraldehyde (GA) is used at a concentration around 2% for the cold sterilization of endoscopy and dental instruments. Stock GA solution (pH 3.1-4.5) is alkalinized (pH 7.8-8.0) before use to optimize biocidal activity. The possible differential handling hazards between acidic unbuffered GA (UGA) and alkaline buffered GA (BGA) were compared for acute toxicity, primary irritancy and skin sensitizing potential using a 2.2% GA solution. Peroral LD5.0 values (with 95% confidence limits) in rats (combined sexes) were 3.45 (3.13-3.80) g/kg for UGA and 4.16 (3.13-5.52) g/kg for BGA; signs and gross pathology were similar. A 24-h occluded cutaneous application of 16.0 g/kg in the rabbit did not produce mortality; moderate skin irritancy was observed. No systemic effects occurred with UGA and only a few with BGA (unsteady gait, sluggishness, rapid breathing). Local skin irritation from a 4-h occluded contact with 0.5 ml was relatively minor and slightly more marked with BGA than UGA. Rats exposed to a statistically generated saturated vapor atmosphere for 6 h did not show any signs or gross pathology, and only slight weight loss occurred (UGA females). Rabbit eye irritation studies (0.1 ml) showed slightly more marked conjunctival reactions with BGA, but corneal injury was marked and persistent with BGA and only slight and transient with UGA. With 0.01 ml, no corneal injury occurred, but conjunctival reaction was more marked with UGA. A guinea pig maximization study showed UGA to produce a higher sensitizing index (68% at challenge, 32% at rechallenge) than BGA (30% at challenge, 5% at rechallenge). Severity indices at challenge was also higher for UGA [0.84 (24 h), 0.47 (48 h)] than BGA [0.45 (24 h), 0.18 (48 h)]. Both UGA and BGA have generally similar acute toxicity and skin irritancy; BGA has greater corneal injuring potential, and UGA has a greater skin sensitizing potential.

Comparative acute toxicity and primary irritancy of the ethylidene and vinyl isomers of norbornene

The acute toxicity and primary irritancy of the industrial chemicals 5-ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB) were studied. They are of moderate acute peroral toxicity in the rat, with LD50 values for ENB of 2.54 (male) and 5.66 (female) ml kg(-1), and for VNB of 5.90 (male) and 11.9 (female) ml kg(-1). Percutaneous toxicity is slight in the rabbit by 24-h occluded contact, with no mortalities for ENB up to 8.0 ml kg(-1) and only one mortality (male) at 16.0 ml kg(-1) VNB. Dynamically generated saturated vapor atmosphere LT50 values for ENB in the rat were 75 (male) and 125 (female) min, and for VNB they were 28 (male) and 37 (female) min. The 4-h LC50 values for ENB were 2717 (male) and 3015 (female) ppm, and for VNB they were 2231 (male) and 2518 (female) ppm. Intravenously, the ENB LD50 ranged from 0.09 (male rabbit) to 0.11 ml kg(-1) (female); corresponding LD50 values for VNB were 0.10-0.05 mg kg(-1). Acute neurotoxic signs were seen by the intravenous and inhalation routes of exposure, including tremors, ataxia and convulsions; the latter were sufficient to cause vertebral column luxation or fracture, producing spinal cord compression and resultant hindlimb paralysis. Both ENB and VNB are moderately irritating to the skin (rabbit), causing erythema and edema, but not necrosis. Both materials cause slight conjunctival hyperemia and chemosis in rabbits, but not corneal injury.

Decline in the Tropospheric Abundance of Halogen from Halocarbons: Implications for Stratospheric Ozone Depletion

Analyses of air sampled from remote locations across the globe reveal that tropospheric chlorine attributable to anthropogenic halocarbons peaked near the beginning of 1994 and was decreasing at a rate of 25 &plusmn; 5 parts per trillion per year by mid-1995. Although bromine from halons was still increasing in mid-1995, the summed abundance of these halogens in the troposphere is decreasing. To assess the effect of this trend on stratospheric ozone, estimates of the future stratospheric abundance of ozone-depleting gases were made for mid-latitude and polar regions on the basis of these tropospheric measurements. These results suggest that the amount of reactive chlorine and bromine will reach a maximum in the stratosphere between 1997 and 1999 and will decline thereafter if limits outlined in the adjusted and amended Montreal Protocol on Substances That Deplete the Ozone Layer are not exceeded in future years.

The acute toxicity, primary irritancy and skin sensitizing potential of glutaric anhydride

Glutaric anhydride (GA), an industrial chemical, was found of moderate acute peroral lethal toxicity with LD50 values (95% confidence limits) in the rat of 1.41 (0.80-2.49) g/kg (males) and 0.54 (0.36-0.79) g/kg (females), with death being due in part to gastrointestinal irritancy. Dilution with water given by gavage after peroral dosing had no effect on lethal toxicity. Acute percutaneous LD50 values (rabbit) by 24-h occlusion were 6.25 (5.34-7.33) g/kg in males and 5.66 (3.21-9.95) g/kg in females; local skin effects included erythema, edema, necrosis and ulceration. A 6-h exposure to a statically generated saturated vapor atmosphere (rat) produced no signs of toxicity or irritancy. A 4-h, but not 1-h or 3-min occluded contact with 0.5 g of moistened GA (rabbit) produced erythema, edema and necrosis. Contamination of the eye (rabbit) with 10 mg GA produced conjunctivitis (hyperemia, chemosis and discharge) which persisted 7 to 14 d, mild iritis of 2 to 14 d duration, and mild to severe corneal injury which healed within 14 d. A maximization study in guinea pigs by the method of Magnusson and Kligman showed no potential for skin sensitization with GA. The major acute hazards of GA were by swallowing, eye contact and sustained skin contact.

Evaluation of intravenous administration of concentrated immunoglobulin G to colostrum-deprived foals

Ten foals of various breeds were deprived of colostrum from birth to 36 hours of age, then were allotted to 2 groups. Foals of group 1 (n = 6) were given 20 g (200 ml) of purified equine IgG IV in a 10% solution, and foals of group 2 (n = 4) were given 30 g (300 ml) of the same preparation. Total administration time for each 10 g of IgG in 100 ml was approximately 10 minutes. Serum IgG concentration in foals was assessed prior to, between 24 and 48 hours, and at 7 and 14 days after IgG administration. Between 24 and 48 hours after IgG administration, mean serum IgG concentration in group-1 foals was 425 mg/dl (range, 350 to 480 mg/dl). Mean body weight for this group of foals was 50.3 kg (range, 43.3 to 54.7 kg). For group-2 foals, mean serum IgG concentration was 768 mg/dl (range, 640 to 920 mg/dl) between 24 and 48 hours after administration of IgG. Foals of this group had mean body weight of 43.2 kg (range, 36.5 to 47.5 kg). Serum IgG concentration in group-2 foals at 24 to 48 hours was significantly (P = 0.005) greater than that in group-1 foals. Mean total IgG recovery at 24 to 48 hours, calculated on the basis of 94.5 ml of plasma volume/kg of body weight, was approximately 100%. Values of IgG measured in all foals 1 and 2 weeks after administration of the IgG concentrate were equivalent to values expected after normal decay of passively acquired IgG.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemiluminescence in a macrophage cell line modulated by biological response modifiers

We have studied a murine macrophage cell line, J774, and found these cells capable of a zymosan-triggered chemiluminescent oxidative burst. Such activity was enhanced by preincubation with Corynebacterium parvum (CP), bacillus Calmette-Guerin, and lipopolysaccharide (LPS). Under similar conditions, CP and LPS were shown to enhance J774-mediated tumor cell lysis. We have also demonstrated that murine interferon alpha + beta rendered J774 cells more sensitive to the actions of CP and LPS. These results indicate that J774 cells may be useful for the in vitro evaluation of biological response modifiers as well as the study of oxygen radical production by macrophages.

Modulation of hematoporphyrin derivative-sensitized phototherapy with corynebacterium parvum in murine transitional cell carcinoma

The interaction of photodynamic therapy (PDT) with hematoporphyrin derivative (Hpd) and immunotherapy with Corynebacterium parvum (CP) was studied in a murine transitional cell carcinoma (MBT-2) model. C3H/He mice were transplanted subcutaneously in the hind limb with 2.5 X 10(5) tumor cells. One day after transplantation, mice were randomized into groups to receive saline (control), PDT, CP 25 micrograms, CP 250 micrograms, CP 25 micrograms + PDT, and CP 250 micrograms + PDT. PDT was administered by intraperitoneal (IP) injection of Hpd (12.5 micrograms/g body weight), followed twenty-four hours later by photoirradiation. CP was given intralesionally at the same time as IP injection of Hpd (24 hours before photoirradiation). A low dose of CP (25 micrograms) was shown to enhance the effect of PDT while PDT reduced the benefit obtained with high dose of CP (250 micrograms). In a second series of experiments, CP (250 micrograms) treatment after photoirradiation was shown to give significantly greater benefit than CP treatment before photoirradiation. The study thus indicates that the effectiveness of combined immunophototherapy is dependent on the sequence of the combination and its intricate relationship with the dosage of CP. The enhancement of PDT by low dose of CP in this model suggests the usefulness of this combined immunophototherapy in enhancing tumor control and in lessening deleterious side effects.

The acute toxicity of tris(dimethylamino)silane

The acute handling hazards of tris(dimethylamino)silane [TDMAS] were investigated. The acute male rat peroral LD50 (with 95% confidence limits) was 0.71 (0.51-0.97) ml/kg, and the acute male rabbit percutaneous LD50 was 0.57 (0.35-0.92) ml/kg. The liquid was severely irritating to the rabbit eye and skin, and the vapor severely irritating to the rat eye. The dynamically generated saturated vapor Lt50 in female rats was 12 (9.7-15) min. The effect of varying the atmospheric concentration of vapor from TDMAS on acute inhalation toxicity was investigated by passing ordinary moist air countercurrent to liquid TDMAS metered into a slightly heated glass tube. Based on nominal concentrations, the 4 hr-LC50 for vapor from TDMAS was 734 (603-893) ppm in female rats by this procedure. Stoichiometrically, this accords with toxicity due to liberation of dimethylamine (DMA) from TDMAS. In a subsequent study designed to assess the influence of relative humidity on vapor toxicity, nitrogen was passed over heated liquid TDMAS and the resultant atmosphere was introduced into the air intake duct of the inhalation exposure chamber. Gas chromatographically measured TDMAS concentrations (+/- SD) were 395 +/- 111, 127 +/- 25, 62 +/- 8 and 23 +/- 21 ppm; the corresponding DMA vapor concentrations were 112 +/- 171, 31 +/- 43, 10 +/- 6 and 26 +/- 44 ppm. The 4-hr LC50 (males and females) was 38 (34-43) ppm TDMAS vapor. Thus, TDMAS is of moderate acute peroral and percutaneous toxicity, a severe primary skin and eye irritant, an aspiration hazard, and of high intrinsic acute inhalation toxicity, but in moist air conditions lethal toxicity may be reduced and in such circumstances DMA may be a significant factor in toxicity.