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Biomedical subjects

D Weiss

Publications and source records attributed to D Weiss.

At least 19 recordsLinked to original sources
PubMed2006

Magnetic vortex core reversal by excitation with short bursts of an alternating field.

The vortex state, characterized by a curling magnetization, is one of the equilibrium configurations of soft magnetic materials and occurs in thin ferromagnetic square and disk-shaped elements of micrometre size and below. The interplay between the magnetostatic and the exchange energy favours an in-plane, closed flux domain structure. This curling magnetization turns out of the plane at the centre of the vortex structure, in an area with a radius of about 10 nanometres--the vortex core. The vortex state has a specific excitation mode: the in-plane gyration of the vortex structure about its equilibrium position. The sense of gyration is determined by the vortex core polarization. Here we report on the controlled manipulation of the vortex core polarization by excitation with small bursts of an alternating magnetic field. The vortex motion was imaged by time-resolved scanning transmission X-ray microscopy. We demonstrate that the sense of gyration of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT. This reversal unambiguously indicates a switching of the out-of-plane core polarization. The observed switching mechanism, which can be understood in the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application in data storage.

Journal Article↗
PubMed2006

Dephasing in (Ga,Mn)As nanowires and rings.

To understand quantum mechanical transport in a ferromagnetic semiconductor, the knowledge of basic material properties such as the phase coherence length and corresponding dephasing mechanism are indispensable ingredients. The lack of observable quantum phenomena has prevented experimental access to these quantities so far. Here we report the observations of universal conductance fluctuations in ferromagnetic (Ga,Mn)As. The analysis of the length and temperature dependence of the fluctuations reveals a T(-1) dependence of the dephasing time.

Journal Article↗
PubMed2006

Optical and dosimetric properties of zircon.

Irradiation effects were investigated in zircon crystals by methods of optical absorption and luminescence. Special attention was given to the effects of vacuum ultraviolet (VUV) radiation. The same main thermoluminescence (TL) peaks with the same thermal activation energies appeared after VUV as after X- or beta irradiation, indicating that the same traps were induced by the different irradiations. TL excitation spectra in the VUV showed an increase <220 nm and maxima near 190 and 140 nm. Excitation spectra of phototransferred TL (PTTL) and optically stimulated luminescence (OSL) were also measured. Most TL emission bands also appeared in the X-luminescence, PTTL and OSL. Dosimetric properties such as the TL radiation sensitivity, thermal stability of radiation-induced defects and TL dose dependence were also investigated. The radiation sensitivity of zircon was by an order of magnitude lower than that of TLD-100. The 355 K TL peak showed linear dose dependence only up to approximately 500 Gy and the 520 K peak up to approximately 1800 Gy.

Dose-Response Relationship, Radiation↗
PubMed2006

Optical excitation of LiF:Mg,Ti following alpha and beta irradiation.

It is demonstrated experimentally that optical excitation of irradiated LiF:Mg,Ti (TLD-100) by 4 eV photons has the same effect for both alpha particle (high-ionisation density) irradiation and photon/electron irradiation. In both cases, peak 5a converts to peak 4 causing peak 4 to increase following the bleach. Such an observation is consistent with the major premise of track structure theory that radiation effects following heavy changed particle (HCP)/neutron irradiation are due exclusively to the interaction of the secondary electrons created by the HCP slowing down.

Alpha Particles↗
PubMed2006

[Lightning injuries: case report of a 17-year-old man and a brief review of the literature].

Lightning injury is one of the most frequent injuries caused by a natural phenomenon, but the risk of being struck by lightning is low. The most vulnerable subjects for lightning injuries are individuals who work in open fields. Although lightning injuries may involve all organ systems, injuries to the cardiovascular system and central nervous system are the most frequent. Burns, tinnitus, blindness and secondary blunt trauma have also been reported. Even though immediate death through lightning-induced cardiac arrest is well documented, the majority of cases reported in the literature describe infrequent and enormously disparate sequelae.A 17-year-old man was admitted to our hospital approximately 3 h after a lightning strike. The Glasgow coma scale was recorded as 15/15 and partial thickness burns totaling of 11% were present on the chest, stomach and right and left lower leg. The entry point was approximately the right side of the neck and the current exited through the right foot. On arrival, the patient's vital signs were normal. Cardiac and pulmonary examinations were within normal limits. The patient suffered transient symptoms, including pain, loss of consciousness, tinnitus, iritis and paresthesia. The laboratory data obtained on admission were within normal limits except serum for WBC, CK, CK-MB, troponin and CRP. We postulate that the mechanism by which lightning caused injury to this patient was a flash discharge (side splash). During his stay in hospital, a debridement of the burn surface following graft coverage and Z-plasty to close the dehiscent wound on the right neck was performed. The patient was discharged from the hospital after 14 days.

Adolescent↗
PubMed2005

Genome scan of schizophrenia families in a large Veterans Affairs Cooperative Study sample: evidence for linkage to 18p11.32 and for racial heterogeneity on chromosomes 6 and 14.

Genome-wide linkage analyses of schizophrenia have identified several regions that may harbor schizophrenia susceptibility genes but, given the complex etiology of the disorder, it is unlikely that all susceptibility regions have been detected. We report results from a genome scan of 166 schizophrenia families collected through the Department of Veterans Affairs Cooperative Studies Program. Our definition of affection status included schizophrenia and schizoaffective disorder, depressed type and we defined families as European American (EA) and African American (AA) based on the probands' and parents' races based on data collected by interviewing the probands. We also assessed evidence for racial heterogeneity in the regions most suggestive of linkage. The maximum LOD score across the genome was 2.96 for chromosome 18, at 0.5 cM in the combined race sample. Both racial groups showed LOD scores greater than 1.0 for chromosome 18. The empirical P-value associated with that LOD score is 0.04 assuming a single genome scan for the combined sample with race narrowly defined, and 0.06 for the combined sample allowing for broad and narrow definitions of race. The empirical P-value of observing a LOD score as large as 2.96 in the combined sample, and of at least 1.0 in each racial group, allowing for narrow and broad racial definitions, is 0.04. Evidence for the second and third largest linkage signals come solely from the AA sample on chromosomes 6 (LOD = 2.11 at 33.2 cM) and 14 (LOD = 2.13 at 51.0). The linkage evidence differed between the AA and EA samples (chromosome 6 P-value = 0.007 and chromosome 14 P-value = 0.004).

Adult↗
PubMed2005

Andreev reflection at high magnetic fields: evidence for electron and hole transport in edge states.

We have studied magnetotransport in arrays of niobium filled grooves in an InAs/Al(x)Ga(1-x)Sb heterostructure. The critical field of up to 2.6 T permits one to enter the quantum Hall regime. In the superconducting state, we observe strong magnetoresistance oscillations, whose amplitude exceeds the Shubnikov-de Haas oscillations by a factor of about 2, when normalized to the background. Additionally, we find that above a geometry-dependent magnetic field value the sample in the superconducting state has a higher longitudinal resistance than in the normal state. Both observations can be explained with edge channels populated with electrons and Andreev-reflected holes.

Journal Article↗
PubMed2005

Monitoring over-the-counter medication sales for early detection of disease outbreaks--New York City.

INTRODUCTION: Over-the-counter (OTC) medications are frequently used during the initial phase of illness, and increases in their sales might serve as an early indicator of communitywide disease outbreaks. Since August 2002, the New York City (NYC) Department of Health and Mental Hygiene (DOHMH) has tracked OTC medication sales to enhance detection of natural and intentional infectious disease outbreaks. OBJECTIVES: This report describes the surveillance system and presents results from retrospective analyses and a comparison between citywide trends in OTC medication sales and emergency department (ED) visits. METHODS: Sales data transmitted daily to DOHMH are categorized into two groups: influenza-like illness (ILI), which includes cough and influenza medications, and gastrointestinal illness (GI), which includes major brand and generic antidiarrheals. Cyclical, linear regression models were used to identify significant (p<0.05) increases in the daily ratio of ILI to analgesics sales (analgesics are used as a denominator in the absence of total sales). Daily and weekly average ratios of GI to analgesic sales were analyzed. Citywide trends in OTC ILI and GI medication sales were compared with ED visits for fever/influenza and diarrhea syndromes. RESULTS: Citywide ILI drug sales were highest during annual influenza epidemics and elevated during spring and fall allergy seasons, similar to trends in the ED fever/influenza syndrome. ILI sales did not consistently provide earlier warning than the ED system of communitywide influenza. GI drug sales increased during the fall and peaked during early winter and after the blackout of August 2003. Unlike ED diarrheal visits, GI medication sales did not substantially increase during late winter (February-March). CONCLUSION: Citywide OTC medication sales can provide indications of communitywide illness, including annual influenza epidemics. Antidiarrheal medication sales were more sensitive to increases in GI caused by norovirus and influenza than illness caused by rotavirus. OTC medication sales can be considered as an adjunct syndromic surveillance system but might not be as sensitive as ED systems.

Commerce↗
PubMed2005

Three years of emergency department gastrointestinal syndromic surveillance in New York City: what have we found?

BACKGROUND: Use of syndromic surveillance as a tool to detect outbreaks and potential biologic or chemical terrorist attacks is increasing. Evaluating health departments' use of syndromic surveillance is necessary to determine the value of this methodology. METHODS: Syndromic surveillance signals detected by the New York City Department of Health and Mental Hygiene (DOHMH) during November 2001-August 2004 were reviewed for diarrhea and vomiting syndromes, the methods used to investigate such signals, and results of these investigations to determine if any unreported outbreaks were detected. Gastrointestinal (GI) outbreaks reported to DOHMH also were reviewed to understand why they were not detected by DOHMH's Emergency Department (ED) syndromic surveillance system. RESULTS: During the study period, ED surveillance generated 98 citywide and 138 spatial GI signals. Multiple outbreaks suspected to be caused by norovirus and rotavirus were identified, as well as a citywide increase in diarrheal illness. Of 98 citywide signals detected, 73 (75%) occurred during seasonal outbreaks. During the same period, 49 GI outbreaks were reported to DOHMH; none was detected simultaneously by ED surveillance. CONCLUSION: Only substantial, citywide syndromic signals were identified as outbreaks and routinely reported. GI outbreaks did not generate syndromic signals. Syndromic surveillance signals occur frequently, are difficult to investigate satisfactorily, and should be viewed as a supplement to, rather than a replacement for, well-maintained traditional surveillance systems that rely on strong ties between clinicians and public health authorities.

Disease Outbreaks↗
PubMed2005

X-Ray storage luminescence of BaFCl:Eu2+ single crystals.

Temperature behaviors of X-ray luminescence (XL), photoluminescence (PL), photostimulated luminescence, and thermoluminescence (TL) were studied in BaFCl:Eu2+ single crystals from room temperature to liquid nitrogen temperature. Six emissions at 275, 315, 365, 385, 435, and 500 nm were observed in the XL spectra and are attributed to Cl excitons, V(k)(Cl2-), the 4f65d1 (2e(g)) --> 4f7 (8S(7/2)) transition of Eu2+, and oxygen vacancies, respectively. Three emission peaks at 315, 365, and 390 nm were observed in the PL and TL measurements. These three emissions are from the transitions of 4f7(6I(7/2)) --> 4f7(8S(7/2)), 4f7(6P(7/2)) --> 4f7(8S(7/2)), and 4f65d1 (2e(g)) --> 4f7(8S(7/2)) of Eu2+, respectively. In our measurements, we observed that the emission of Eu2+ increases in intensity upon beta-irradiation and did not see any signals related to Eu3+ ions, which indicates that Eu2+ ions might not be oxidized to Eu3+ upon X-ray or beta-irradiation. Instead, the color centers, Cl excitons, and oxygen defects are created and are stable at room temperature, and they might play a key role in the storage luminescence.

Barium Compounds↗
PubMed2005

Optimization of individual prestimulation in dairy cows.

The application of prestimulation results in enhanced milking performance compared with milking without prestimulation. In the present study oxytocin (OT) release and milking characteristics were investigated in 43 dairy cows after the application of various prestimulation routines by vibration stimulation lasting between 0 and 90 s. Additionally, different maximum pulsation vacuum settings during vibration stimulation were investigated. The actual degree of udder fill was calculated as a percentage of the estimated storage capacity. The amplitude of OT release, total milk yield, and stripping milk yield did not differ between prestimulation routines. Increased maximum pulsation vacuum during vibration stimulation resulted in milk flow during prestimulation, but did not negatively influence milking characteristics. The lag time from the start of teat stimulation until the start of milk ejection was negatively correlated with the degree of udder fill. This relationship was the reason for variations in optimal duration of prestimulation. The optimal duration of prestimulation to receive immediate and continuous milk flow at the start of milking was 90 s in udders containing small amounts of milk, whereas the optimal duration was only 20 s in well-filled udders. A short prestimulation enhances milking stall capacity when milking full udders, and a prolonged prestimulation reduces the total vacuum load on the teat when milking udders that are not full.

Animals↗
PubMed2004

New York City syndromic surveillance systems.

New York City's first syndromic surveillance systems were established in 1995 to detect outbreaks of waterborne illness. In 1998, daily monitoring of ambulance dispatch calls for influenza-like illness began. After the 2001 World Trade Center attacks, concern about biologic terrorism led to the development of surveillance systems to track chief complaints of patients reporting to emergency departments, over-the-counter and prescription pharmacy sales, and worker absenteeism. These systems have proved useful for detecting substantial citywide increases in common viral illnesses (e.g., influenza, norovirus, and rotavirus). However, the systems have not detected more contained outbreaks earlier than traditional surveillance. Future plans include monitoring school health and outpatient clinic visits, augmenting laboratory testing to confirm syndromic signals, and conducting evaluation studies to identify which of these systems will be continued for the long term.

Bioterrorism↗
PubMed2004

Field investigations of emergency department syndromic surveillance signals--New York City.

INTRODUCTION: The New York City (NYC) Department of Health and Mental Hygiene (DOHMH) has operated a syndromic surveillance system based on emergency department (ED) chief-complaint data since November 2001. This system was created for early detection of infectious-disease outbreaks, either natural or intentional. However, limited documentation exists regarding epidemiologic field investigations conducted in response to syndromic surveillance signals. OBJECTIVE: DOHMH conducted field investigations to characterize syndromic surveillance signals by person, place, and time and to determine whether signals represented true infectious-disease outbreaks. METHODS: A DOHMH physician reviews ED-based syndromic surveillance results daily to look for signals. When necessary, field investigations are conducted and consist of a review of the patient line list, telephone interviews with hospital staff, chart reviews, interviews with patients, and collection and testing of specimens. RESULTS: In November 2002, a series of citywide signals for diarrhea and vomiting syndromes, which coincided with institutional outbreaks consistent with viral gastroenteritis, prompted DOHMH to send mass e-mail notification to NYC ED directors and institute collection of stool specimens. Three of four specimens collected were positive for norovirus. In December 2002, DOHMH investigated why an ED syndromic signal was not generated after 15 ill patients were transferred to a participating ED during a gastrointestinal outbreak at a nursing home. Field investigation revealed varying chief complaints, multiple dates of ED visits, and a coding error in a complementary DOHMH syndromic system, and confirmed a seasonal norovirus outbreak. During March 2003, the system generated a 4-day citywide respiratory signal and a simultaneous 1-day hospital-level fever signal in a predominantly Asian community. In those instances, epidemiologic investigation provided reassurance that severe acute respiratory syndrome was not present. CONCLUSION: Detailed field investigations of syndromic signals can identify the etiology of signals and determine why a given syndromic surveillance system failed to detect an outbreak captured through traditional surveillance. Validation of the utility of syndromic surveillance to detect infectious-disease outbreaks is necessary to justify allocating resources for this new public health tool.

Communicable Diseases, Emerging↗
PubMed2004

Fourier transform imaging of spin vortex eigenmodes.

Thin-circular lithographically defined magnetic elements with a spin vortex configuration are excited with a short perpendicular magnetic field pulse. We report the first images of excited magnetic eigenmodes up to third order, obtained by means of a phase sensitive Fourier transform imaging technique. Both axially symmetric and symmetry breaking azimuthal eigenmodes are observed. We observe strong oscillations of the magnetization in the central part of the magnetic elements. The experimental data are in good agreement with micromagnetic simulations.

Journal Article↗
PubMed2004

Experimental separation of Rashba and Dresselhaus spin splittings in semiconductor quantum wells.

The relative strengths of Rashba and Dresselhaus terms describing the spin-orbit coupling in semiconductor quantum well (QW) structures are extracted from photocurrent measurements on n-type InAs QWs containing a two-dimensional electron gas (2DEG). This novel technique makes use of the angular distribution of the spin-galvanic effect at certain directions of spin orientation in the plane of a QW. The ratio of the relevant Rashba and Dresselhaus coefficients can be deduced directly from experiment and does not relay on theoretically obtained quantities. Thus our experiments open a new way to determine the different contributions to spin-orbit coupling.

Journal Article↗
PubMed2004

Development of an ombrotrophic peat bog (low ash) reference material for the determination of elemental concentrations.

Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail.

Environmental Monitoring↗
PubMed2004

The acyclic period postpartum in automatic and conventional milking.

The acyclic postpartum period in cows is prolonged due to frequent suckling when compared with twice daily milking. In conventional milking systems twice daily milking is common, while in automatic milking systems (AMS) three or more milkings are performed in early lactation. In this study, the hypothesis was tested that an increased milking frequency in AMS causes a delay in resumption of ovarian cyclicity postpartum and increases days open in German Fleckvieh cows (n = 124). Calvings were equally distributed throughout the 1-year experimental period. All cows were housed in one barn. Sixty-three cows were milked in an AMS (AC) and 61 cows were twice daily milked in a conventional milking parlour (PC). Forty-two AC and 36 PC remained in the herd until conception. After parturition, milk samples were analysed for progesterone twice weekly to record the ovarian activity until pregnancy was diagnosed. The first and the second ovulation were determined by the progesterone profile of each individual cow. The mean milking frequency during the first 3 weeks after parturition was higher in AC (3.17 +/- 0.09 milkings/day) than in PC (milked twice daily). The individual mean milking frequency of AC for the first 3 weeks of lactation ranged from 2.0 to 5.9 daily milkings. The time span from parturition until the first and second ovulation did not differ between AC and PC. However, first ovulation was observed earlier in primiparous (23 +/- 1 days) than in multiparous cows (29 +/- 1 days, P < 0.05). Within AC no relationship between milking frequency and duration of the acyclic period was observed. Days open did not significantly differ between AC and PC and between primiparous and multiparous cows. In conclusion, the increased milking frequency in AMS did neither cause a delay in resumption of ovarian cyclicity postpartum nor did it increase days open.

Anestrus↗