Impact of antibiotics on spermatozoa quality and bacterial load of chilled-stored camels (Camelus dromedarius) semen.

This experiment was conducted to assess the effect of different antibiotics in tris-fructose egg yolk-based diluent on bacterial load and sperm quality of dromedary camels during processing and cold storage. Ten semen ejaculates were collected from five male dromedary camels. Each sample was fractioned into four equally divided aliquots and diluted in one of four tris-fructose egg yolk. The first extender contained no antibiotic (NC). The second extender included streptomycin sulphate (1000 µg/ml) and benzyl penicillin (1000 IU/ml) (SP). The third extender was supplied with 250 µg/ml gentamicin sulphate (Gent). The fourth extender contained 500 µg/ml gentamicin sulphate,100 µg/ml tylosin tartrate, 300 µg/ml lincomycin hydrochloride and 600 µg/ml spectinomycin hydrochloride (GTLS). After dilution, the extended semen samples were cooled to 5 °C within 2 h and finally stored at 5 °C for 72 h. Microbial concentration, motility of spermatozoa, live spermatozoa, plasma membrane and acrosome integrity percentages were evaluated just after dilution at 35 °C, 0, 24, 48 and 72 h from the start of cooling to 5 °C. The results revealed that the diluent containing gentamicin had significantly (P<0.05) maximum motility percentage at the different examination intervals. The pattern of live spermatozoa percentage was varied between the different treatments at different examination intervals. The diluent supplied with Gent was distinguished with a significant peak percentage (P<0.05) of swelled spermatozoa among the other antibiotics supplied diluents. The number of colony-forming units isolated from the semen samples kept in diluent containing no antibiotics was significantly (P<0.05) higher than that isolated from the diluents supplemented with antibiotics. In conclusion, the semen diluents fortified with gentamicin generally keep the motility, acrosomal and plasma membrane integrity and live spermatozoa for 72-h preservation of dromedary semen.

Gene expression of heat shoc kproteins/factors (HSP60, HSP70, HSP90, HSF-1, HSF-3) and antioxidant enzyme activities in heat stressed broilers treated with vitamin C.

In broiler chickens, the relationship between dietary supplementation of vitamin C and hepatic, cardiac and renal heat shock proteins (HSP60, HSP70 and HSP90), heat shock factors (HSF-1 and HSF-3) and enzymatic antioxidants requires further investigation. The current study aimed to investigate this relationship at cellular and molecular levels in a 42 days experiment. Two hundred, one-day-old broiler chicks (Ross 308) were allocated into four equal groups. Chicks in the first and third groups were thermo-neutral (TN; 22°C for 24 hours/day) and fed basal diet without or with vitamin C (1g/kg basal diet), respectively. Chicks in the second and fourth groups were heat stressed (HS; 34°C for 8 hours/day) and fed basal diet without or with vitamin C, respectively. Performance parameters were recorded throughout the experiment. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX), Catalase (CAT) and gene expression of heat shock proteins (HSP60, 70 and 90) and heat shock factors (HSF 1 and 3) were analyzed in liver, heart and kidney tissues of the studied groups. Heat stress induced a negative impact on performance parameters, significant reduction in activities of all examined antioxidant enzymes and a significant up-regulation in heat shock proteins and factors genes in all studied tissues. Dietary supplementation of vitamin C corrected these parameters towards the normal control values. Conclusively, dietary supplementation of the examined dose of vitamin C was efficient at ameliorating the detrimental effects of heat stress on liver, heart and kidney tissues of broilers chickens at cellular and molecular levels.

Effect of heavy metals arsenic, cadmium, and lead on the semen variables of dromedary camels (Camelus dromedarius).

In this study, there was investigation of the effect of heavy metals on the fertility of dromedary camels. Fourteen camels at the Camel Research Center, King Faisal University, and 41 infertile dromedaries admitted to the Veterinary Teaching Hospital were used for semen evaluation during the breeding season. Seminal plasma and blood serum were collected from all males until analysis. Concentrations of three heavy metals [arsenic (As), cadmium (Cd), and lead (Pb)] were determined in the seminal plasma and serum using an atomic absorption spectrophotometer. The results indicate there are differences (P < 0.05 - P < 0.01) in pH, sperm motility, sperm concentration, and sperm abnormalities between the fertile and infertile male camels. In seminal plasma, there were marked differences (P < 0.01- P < 0.0001) between the control and infertile male camels in As, Cd, and Pb concentrations. In serum, there were differences (P < 0.01 - P < 0.001) between the fertile and infertile camels in serum As, Cd, and Pb concentrations. There was a positive correlation (P < 0.05; r = 0.77 and r = 0.94, respectively) between serum and seminal plasma concentrations of both As and Cd in the infertile dromedaries. In the control group, there was a positive correlation (P < 0.05; r = 0.70) between seminal plasma concentrations of Cd and percent sperm abnormalities. In conclusion, relatively greater seminal plasma and serum concentrations of As, Cd, and Pb are associated with lesser values for semen quality variables and infertility in dromedary camels.

Acute-phase proteins, oxidative stress biomarkers, proinflammatory cytokines, and cardiac troponin in Arabian mares affected with pyometra.

New biomarkers are essential for diagnosis of pyometra in mares. In this context, 12 subfertile Arabian mares suffered from pyometra were admitted to the Veterinary Teaching Hospital. The basis for diagnosis of pyometra was positive findings of clinical examination and rectal palpation. Blood samples were collected from diseased animals and from five Arabian healthy mares, which were considered as control group. Acute-phase proteins (APP), oxidative stress biomarkers, proinflammatory cytokines, and cardiac troponin I were estimated in the harvested sera of both groups. Clinical examination revealed purulent yellowish fluid discharged from vagina of affected animals and rectal palpation of the reproductive tract revealed uterine distention. The biochemical analysis of the serum revealed significant increase in cardiac troponin I, creatin kinase, alkaline phosphatase, malondialdehyde, tumor necrosis factor α, interleukins 6, prostaglandin F2α, haptoglobin, and serum amyloid A and significant decrease in reduced glutathione, superoxide dismutase (SOD), total antioxidant capacity, and nitric oxide (NO) of mares affected with pyometra compare to control. Cardiac troponin I was positively correlated with aspartate aminotransferase, creatin kinase, malondialdehyde, alkaline phosphatase, tumor necrosis factor α, interleukins 6, prostaglandin F2α, haptoglobin and serum amyloid A and negatively correlated with glutathione, superoxide dismutase, total antioxidant capacity and nitric oxide in serum of mares affected with pyometra. Moreover, there was high positive correlation between proinflammatory cytokines and APP in serum of mares affected with pyometra. The present study suggests cardiac troponin I together with APP, proinflammatory cytokines, and oxidative stress parameters as biomarkers for pyometra in Arabian mares.

Trypanosoma evansi in naturally infected dromedary camels: lipid profile, oxidative stress parameters, acute phase proteins and proinflammatory cytokines.

Additional biomarkers are essential for control of Trypanosoma evansi (T. evansi) infection in dromedary camels. Two groups of 30 camels each, one naturally infected with T. evansi and other normal healthy were executed. The basis for the infection was the positive findings of clinical examination, blood smears and latex agglutination test. Blood samples of both groups and its harvested serum were used for the estimation of present serobiochemical parameters. The present findings revealed significant decrease (P ⩽ 0.05) in triacylglycerol, cholesterol, high density lipoprotein cholesterol with significant increase (P ⩽ 0.05) in low density lipoprotein cholesterol, beta hydroxyl butyric acids, non-esterified fatty acids, haptoglobin, serum amyloid A, ceruloplasmin, fibrinogen, interleukins, tumour necrosis factor-α, interferon gamma, malondialdehyde, superoxide dismutase, reduced glutathione and catalase of infected camels compared with the control. The present study suggests lipid profile, acute phase proteins, proinflammatory cytokines and oxidative stress parameters as biomarkers for T. evansi infection in camels.

Use of the second-generation antipsychotic, risperidone, and secondary weight gain are associated with an altered gut microbiota in children.

The atypical antipsychotic risperidone (RSP) is often associated with weight gain and cardiometabolic side effects. The mechanisms for these adverse events are poorly understood and, undoubtedly, multifactorial in etiology. In light of growing evidence implicating the gut microbiome in the host's energy regulation and in xenobiotic metabolism, we hypothesized that RSP treatment would be associated with changes in the gut microbiome in children and adolescents. Thus, the impact of chronic (>12 months) and short-term use of RSP on the gut microbiome of pediatric psychiatrically ill male participants was examined in a cross-sectional and prospective (up to 10 months) design, respectively. Chronic treatment with RSP was associated with an increase in body mass index (BMI) and a significantly lower ratio of Bacteroidetes:Firmicutes as compared with antipsychotic-naïve psychiatric controls (ratio=0.15 vs 1.24, respectively; P<0.05). Furthermore, a longitudinal observation, beginning shortly after onset of RSP treatment, revealed a gradual decrease in the Bacteroidetes:Firmicutes ratio over the ensuing months of treatment, in association with BMI gain. Lastly, metagenomic analyses were performed based on extrapolation from 16S ribosomal RNA data using the software package, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Those data indicate that gut microbiota dominating the RSP-treated participants are enriched for pathways that have been implicated in weight gain, such as short-chain fatty acid production.

Biochemical and hormonal analysis of follicular fluid and serum of female dromedary camels (Camelus dromedarius) with different sized ovarian follicles.

The current study aimed to compare some biochemical and hormonal constituents in follicular fluids and serum of female dromedary camels with different sized ovarian follicles. Therefore, follicular fluids from follicles sized 1.1-1.5cm (n=10), 1.6-2.1cm (n=10) and 2.2-2.5cm (n=10) and sera were harvested from 20 female camels. The concentrations of ascorbic acid, glucose, cholesterol and activities of acid phosphatase (ACP) and alkaline phosphatase (ALP) were not changed significantly neither in follicular fluids of all follicle sizes nor in sera of female camels with different sized follicles. The concentrations of estradiol-17ß (E2) in the follicular fluid of follicles sized 2.2-2.5cm were significantly lower (P<0.01) than its corresponding value in follicular fluid of other follicle sizes. The concentrations of progesterone (P4), tri-iodothyronine (T3), thyroxin (T4), cortisol and insulin-like growth factor-1 (IGF-1) remained comparable in follicular fluids of all examined different sized follicles. The concentrations of E2, P4, T3, T4, cortisol and IGF-1 were similar in the serum of camels with different sized follicles. Interestingly, mean concentrations of P4 and IGF-1 in follicular fluids were higher than their corresponding values in sera of camels with different sized follicles and the mean concentrations of glucose, cholesterol, ALP and cortisol in sera were higher than their corresponding values in follicular fluids of the examined camels. With the exception of E2, there were no significant differences in biochemical and hormonal constituents between follicular fluids from different sized follicles.

Effect of curcumin on hepatic antioxidant enzymes activities and gene expressions in rats intoxicated with aflatoxin B1.

Twenty-eight rats were examined in a 5-week experiment to investigate the effect of curcumin on gene expression and activities of hepatic antioxidant enzymes in rats intoxicated with aflatoxin B1 (AFB1 ). The rats were divided into four groups. Rats in 1-4 groups served as control, oral curcumin treated (15 mg/kg body weight), single i.p. dose of AFB1 (3 mg/kg body weight) and combination of single i.p. dose of AFB1 with oral curcumin treated, respectively. AFB1 Liver damage and oxidative stress were evident in untreated AFB1 -intoxicated rats as indicated by a significant elevation in hepatic transaminases, elevation in lipid peroxide biomarkers (thiobarbituric acid reactive substances; TBARS), reduction of reduced glutathione (GSH) concentration, reduction in the activities of antioxidant enzymes namely catalase (CAT), total superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione-S-transferase (GST) and down-regulation of gene expression of these antioxidant enzymes compared to control. Liver sections of rats intoxicated with AFB1 showed a disrupted lobular architecture, scattered necrotic cells and biliary proliferation. Administration of curcumin with AFB1 resulted in amelioration of AFB1 -induced effects compared to untreated AFB1 -intoxicated rats via an up-regulation of antioxidant enzyme gene expression, activation of the expressed genes and increase in the availability of GSH.

Comparison of some biochemical and hormonal constituents of oversized follicles and preovulatory follicles in camels (Camelus dromedarius).

The current study was carried out to compare some biochemical and hormonal constituents in follicular fluids from oversized follicles, preovulatory follicles, and serum in camels (Camelus dromedarius). Follicular fluids from oversized follicles (N = 10), preovulatory follicles (N = 10), and sera were harvested from 20 dromedaries. The follicular fluids and sera were subjected to biochemical and hormonal analysis. The results indicated no significant differences in the concentrations of ascorbic acid, glucose, cholesterol, acid phosphatase, and alkaline phosphatase between follicular fluid from oversized follicles and preovulatory follicles. In addition, there were no significant variations in the level of ascorbic acid, glucose, cholesterol, and acid phosphatase in the serum of animals with oversized follicles and those with preovulatory follicles. Serum alkaline phosphatase was significantly greater (P < 0.05) in camels with oversized follicles. The concentrations of estradiol-17ß (E2) and insulin-like growth factor-1 (IGF-1) in the follicular fluid of oversized follicles were significantly lower (P < 0.01) than that from preovulatory follicles. There were no differences in the concentrations of progesterone, tri-iodothyronine, and thyroxin between follicular fluid from oversized follicles and that of preovulatory follicles. The concentrations of E2, progesterone, tri-iodothyronine, thyroxin, cortisol, and IGF-1 were not different in the serum of camels with oversized follicles and camels with preovulatory follicles. The current study revealed that the significant differences of biochemical and hormonal constituents between follicular fluids from oversized follicles and preovulatory follicles were restricted on E2 and IGF-1. Relaying on the aforementioned outcome we can suggest that oversized follicle phenomenon is a form of follicular atresia of anovulatory follicles.

Immunization against GnRH in the male camel (Camelus dromedarius): effects on sexual behavior, testicular volume, semen characteristics and serum testosterone concentrations.

The effect of immunization against gonadotrophin releasing hormone (GnRH) on sexual behavior, total scrotal size, semen characteristics and serum concentrations of testosterone, was evaluated for 24 wks in sexually mature camels (Camelus dromedarius). Eight bull camels were randomly divided into a treatment and control group. Four male camels were immunized using 2 mg GnRH - tandem-dimer conjugated to ovalbumin, (Pepscan Systems, the Netherlands) administered subcutaneously, 4 wks apart. Control male camels received the same amount of saline solution. Significant decline in serum testosterone level was observed in three immunized camels out of four, whereas one camel showed no effect. The testosterone levels reached to <1.0 ng/mL serum by week 4 after booster injection and remained suppressed through the course of the study. The total testicular volume was not affected until the end of the experiment. In treated animals, the sexual behavior negatively affected after the booster injection. Anti-GnRH vaccine had a seriously detrimental effect on the acrosin amidase activity and normal acrosome percentages in treated male camels. It is concluded that the vaccine was effective in reducing serum testosterone levels and libido, and it had a serious harmful effect on the acrosin amidase activity and percentages of spermatozoa with normal acrosome. The immunogen did not affect the total testicular volume.

Versatile system for the temperature-controlled preparation of oxide crystal surfaces.

We present a versatile system for the preparation of oxide crystal surfaces in the ultra-high vacuum (UHV) at temperatures up to 1300 K. Thermal treatment is accomplished by direct current heating of a tantalum foil in contact with the oxide sample. The sample temperature is measured by a thermocouple at a position close to the crystal and its reading is calibrated against the surface temperature determined by a second thermocouple temporarily attached to the surface. The design of the sample holder is based on a transferable plate originally developed for a commercial UHV scanning probe microscope. The system is, however, also suitable for the use with electron spectroscopy or electron diffraction based surface analytical techniques. We present results for the high-temperature preparation of CeO(2)(111) surfaces with atomically flat terraces exhibiting perfect atomic order and cleanliness as revealed by non-contact atomic force microscopy (NC-AFM) imaging. NC-AFM imaging is, furthermore, used to demonstrate the temperature-controlled aggregation of gold atoms on the CeO(2)(111) surface and their evaporation at high temperatures.

Investigation of selected biochemical parameters of local chickens with different age and sex in Al-Ahsa, Saudi Arabia.

In many species of birds, normal values for hematological and biochemical factors were measured and data base was established as their blood-profiles. In local Saudi chicken, measurement of serum biochemical values, which are important for diagnosis of clinical signs and symptoms when affected by diseases, are limited. Therefore, this study was carried out to investigate serum's biochemical values of local Saudi chicken. Therefore, forty chicks (1 month old; 20 males and 20 females) and another forty chicks (3 month old; 20 males and 20 females) were obtained from the farm of the Veterinary Research Station, King Faisal University, Al-Ahsa, Saudi Arabia and used as materials in the study. Blood samples were collected from all birds and the harvested sera were kept frozen at -20 degrees C until the time of analysis. The present findings indicated no significant difference (p > 0.05) of all examined biochemical parameters between male and female chickens or young and old birds. Interestingly, all investigated biochemical parameters in these chickens were lower than the recorded reference values of other birds except for glucose which exhibited higher values than the reference. The reported lower serum cholesterol and triacylglcerol concentrations might be reflected on their concentrations in meat and protecting human beings from atherosclerosis. Therefore, estimation of lipid profile in these birds is recommended for future study.

Some biochemical characteristics and preservation of epididymal camel spermatozoa (Camelus dromedarius).

Testicles were isolated from thirty five apparently healthy dromedary camels (Camelus dromedarius), aged between 5 to 18 years, in a local slaughterhouse during the rutting season. Epididymal fluid was collected from one epididymis for determination of twelve biochemical and antioxidant parameters using ELISA commercial kits. Spermatozoa were harvested from each region of the other epididymis (head, body and tail) and stored in SHOTOR®, Green buffer® + 20% egg yolk and INRA-96® extenders at 5 and 30 °C. Results revealed that, in the epididymal fluid, concentrations of testosterone, glucose, albumin, total protein, cholesterol, fatty acids, iron, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were 5.19 ± 1.69 ng/mL, 3.10 ± 0.41 mmol/L, 6.26 ± 1.26 g/dL, 0.50 ± 0.07 mg/dL, 1.74 ± 0.09 mmol/L, 6.62 ± 0.81 nmol/ul, 926.20 ± 100.18 ug/dL, 51.17 ± 7.74 mIU/ml, and 143.16 ± 18.67 mIU/ml, respectively. The antioxidants activities of catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD) in the epididymal fluid were 121.55 ± 6.57 nmol/min/ml, 59.35 ± 10.98 nmol/min/ml and 0.18 ± 0.03 U/ml, respectively. Epididymal sperm motility and concentration were higher (P < 0.05) in the body and tail than the head. The viability indices of total and forward sperm motility, at 5 and 30 °C, obtained from the tail region were superior (P < 0.05) in both SHOTOR® and INRA-96® extenders than Green buffer extender. It may be concluded that INRA-96® extender is the best for storing dromedary epididymal spermatozoa at 5 and 30 °C.

Clinical efficacy of a new monofilament fibre-containing wound debridement product.

OBJECTIVE: To evaluate the wound debridement efficacy (that is, achievement of 100% granulation tissue on the wound bed) of a new monofilament fibre product (Debrisoft). METHOD: This multicentre, prospective, observational evaluation assessed the debridement efficacy, safety, patient comfort and user satisfaction of this new product. Time taken to perform the debridement procedure was also recorded. The new product was wetted with either saline or polihexanide and applied for 2-4 minutes, following which the usual dressing regimen was applied. Clinical outcome was scored by a trained clinician. Additionally, before and after photographs were assessed by one and the same clinician, who was blinded to the treatment given. The debridement outcomes achieved with the test product were compared with results obtained using other methods of debridement, both non-surgical and surgical, taken from an electronic database but using the same scoring systems as here. RESULTS: Sixty patients with chronic wounds requiring debridement were recruited, of whom 57 were included in the analysis. Debridement was effective in 93.4% (142/152) of the sessions, and the product remained intact in 95.4% (145/152). The average time for each debridement session was 2.51 minutes, markedly less than for the current debridement methods at the evaluation centres. Visible debris and slough were successfully removed with the test product. Patients reported no pain during the procedure in 45% of cases and slight discomfort for a short duration (2.0 minutes on average) in 55% of cases. CONCLUSION: The results indicate the potential for this monofilament fibre product to replace several modes of debridement, based on its efficacy, short procedure, ease of use and patient comfort. CONFLICT OF INTEREST: The evaluation protocol was proposed and supported by Lohmann & Rauscher GmbH, who provided the evaluation products. MS and MA are employees of Lohmann & Rauscher. The other authors declare to have no relevant financial interest in the evaluation. Apart from input to the protocol, the sponsors had no role in the conduct of the study, such as data collection, analysis, or preparation, review, or approval of the manuscript.

The effect of manipulations of incubation temperature on embryonic and post-hatching growth of native Saudi chickens.

Embryonated egg is an ideal, environment in which to investigate the effects of incubation temperature on the development of the chick embryo. The objective of the current study were to investigate the effect of increasing the incubation temperature of chick embryo by 1.2 degrees C for 7 days (ED4 to ED11) on the body movement and mass of native saudi chick embryo. This objective was extended to examine the influence of pre-hatching temperature on post-hatching growth. Therefore, a total of 180 hatching egg of native Saudi chicken divided into two equal groups incubated at temperature 37.5 degrees C. The incubation temperature was raised to 38.7 degrees C from ED4 to ED11 in treated group before being returned to the control group incubation temperature (37.5 degrees C). The study revealed that elevating the incubation temperature of the eggs of native Saudi chicken by just 1.2 degrees C, from 37.5 to 38.7 degrees C, during embryonic days (ED) 4-11 causes significant increase in embryonic movement as demonstrated in day 8 in the chicks incubated at 38.7 degrees C together with an increase in embryonic development, the embryos incubated at higher temperature were heavier in weights and exhibit significantly longer legs than the controls in ED12 and 15. The increase in pre-hatching incubation temperature (38.7 degrees C) did not reveal any significant effects on post-hatching growth or of feed conversion efficiency.

Interaction of acetonitrile with thin films of solid water.

Thin films of water were prepared on Ag at 124 K. Their properties were studied with metastable impact electron spectroscopy, reflection absorption infrared spectroscopy, and temperature programmed desorption. The interaction of acetonitrile (ACN) with these films was studied with the abovementioned techniques. From the absence of any infrared activity in the initial adsorption stage, it is concluded that ACN adsorbs linearly and that the C identical withN axis is aligned parallel to the water surface (as also found on neat Ag). Initially, the interaction with water surface species involves their dangling OD groups. During the completion of the first adlayer the ACN-ACN lateral interaction becomes of importance as well, and the ACN molecules become tilted with respect to the water surface. ACN shows propensity to stay at the surface after surface adsorption even during annealing up to the onset of desorption. The present results for the ACN-water interaction are compared with available classical molecular dynamics calculations providing the orientation profile for ACN on water as well as the ACN bonding properties.

Investigations with infrared spectroscopy on films of the ionic liquid [EMIM]Tf2N.

The reflection-absorption infrared (RAIRS) spectra of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]Tf 2N) are presented as a function of temperature between 114 and 292 K. A comparison is made with the corresponding infrared spectra (obtained with transmission spectroscopy) from bulk [EMIM]Tf 2N. The liquid and amorphous films show rather similar spectra, indicating that the film structure is similar in both cases. On the other hand, these spectra differ considerably from those of crystalline films. Characteristic differences seen between the film and bulk spectra are attributed to the different structures of the respective networks. There are, however, indications that under all studied conditions the cation-anion interaction is between the C-H groups of the [EMIM] ring and the SO 2 groups of the anion.

Interaction of methanol with amorphous solid water.

The interaction of methanol (MeOH) with amorphous solid water (ASW) composed of D2O molecules, prepared at 125 K on a polycrystalline Ag substrate, was studied with metastable-impact-electron spectroscopy, reflection-absorption infrared spectroscopy, and temperature-programmed desorption mass spectroscopy. In connection with the experiments, classical molecular dynamics (MD) simulations have been performed on a single CH3OH molecule adsorbed at the ice surface (T=190 K), providing further insights into the binding and adsorption properties of the molecule at the ice surface. Consistently with the experimental deductions and previous studies, MeOH is found to adsorb with the hydroxyl group pointing toward dangling bonds of the ice surface, the CH3 group being oriented upwards, slightly tilted with respect to the surface normal. It forms the toplayer up to the onset of the simultaneous desorption of D2O and MeOH. At low coverage the adsorption is dominated by the formation of two strong hydrogen bonds as evidenced by the MD results. During the buildup of the first methanol layer on top of an ASW film the MeOH-MeOH interaction via hydrogen-bond formation becomes of importance as well. The interaction of D2O with solid methanol films and the codeposition of MeOH and D2O were also investigated experimentally; these experiments showed that D2O molecules supplied to a solid methanol film become embedded into the film.

Comparative study of the interaction of pyridine with polycrystalline Ag and amorphous solid water.

The interaction of pyridine (C5H5N) with polycrystalline Ag and amorphous solid water (D2O) is compared. Metastable impact electron spectroscopy (MIES) and reflection-absorption infrared spectroscopy (RAIRS) were utilized to obtain information on the structure of the pyridine-Ag and pyridine-water interfaces. On polycrystalline Ag, C5H5N adsorbs with its molecular axis perpendicular to the surface whereby a work function decrease of 1.5 eV takes place during the build up of the first layer. In the second layer the molecular axis is tilted with respect to the surface normal. On amorphous solid water, C5H5N is initially adsorbed on top with its ring plane oriented preferentially near parallel with respect to the surface, reflecting the contribution of two different interactions to the bonding, the formation of a pi-hydrogen bond, and competitive bonding via the nitrogen lone pair. Coverage-driven reorientation takes place during the completion of the first monolayer and increases the average tilt angle. We have followed the growth of pyridine films up to the third layer which, according to RAIRS, shows clear signs of condensation. No embedding of pyridine species into the underlying water film can be noticed when heating up to desorption. The exposure of a pyridine film at 124 K to D2O molecules does not lead to on top adsorption. Instead, D2O becomes initially embedded into the pyridine film, and RAIRS indicates solvation of the pyridine species.

Pump-probe experiments on the single-molecule magnet Fe8: measurement of excited level lifetimes.

We present magnetization measurements on the single-molecule magnet Fe8 in the presence of pulsed microwave radiation. A pump-probe technique is used with two microwave pulses with frequencies of 107 and 118 GHz and pulse lengths of several nanoseconds to study the spin dynamics via time-resolved magnetization measurements using a Hall probe magnetometer. We find evidence for short spin-phonon relaxation times of the order of 1 micros. The temperature dependence of the spin-phonon relaxation time in our experiments is in good agreement with previously published theoretical results. We also established the presence of very short energy diffusion times that act on a time scale of about 70 ns.