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  <xsd:element abstract="true" id="astc_SecuredPromissoryNote2019NoteMember" name="SecuredPromissoryNote2019NoteMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_SecuredPromissoryNote2020NoteMember" name="SecuredPromissoryNote2020NoteMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_SecuredPromissoryNotesOriginalNotesMember" name="SecuredPromissoryNotesOriginalNotesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_ShareRepurchaseProgramAuthorizedNovember2022Member" name="ShareRepurchaseProgramAuthorizedNovember2022Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_SubleasedFacilityMember" name="SubleasedFacilityMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-11-stockbased-compensation-restricted-stock-activity-details" name="statement-statement-note-11-stockbased-compensation-restricted-stock-activity-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-11-stockbased-compensation-stock-option-activity-summary-details" name="statement-statement-note-11-stockbased-compensation-stock-option-activity-summary-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-11-stockbased-compensation-stock-options-outstanding-details" name="statement-statement-note-11-stockbased-compensation-stock-options-outstanding-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-11-stockbased-compensation-tables" name="statement-statement-note-11-stockbased-compensation-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-2-investments-schedule-of-investments-details" name="statement-statement-note-2-investments-schedule-of-investments-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-2-investments-tables" name="statement-statement-note-2-investments-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-3-leases-schedule-of-balance-sheet-presentation-of-operating-and-finance-leases-details" name="statement-statement-note-3-leases-schedule-of-balance-sheet-presentation-of-operating-and-finance-leases-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-3-leases-schedule-of-future-minimum-lease-payments-details" name="statement-statement-note-3-leases-schedule-of-future-minimum-lease-payments-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-3-leases-schedule-of-other-information-details" name="statement-statement-note-3-leases-schedule-of-other-information-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-3-leases-tables" name="statement-statement-note-3-leases-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-4-property-and-equipment-net-tables" name="statement-statement-note-4-property-and-equipment-net-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-4-property-and-equipment-schedule-of-property-and-equipment-details" name="statement-statement-note-4-property-and-equipment-schedule-of-property-and-equipment-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-5-stockholders-equity-schedule-of-warrant-activity-details" name="statement-statement-note-5-stockholders-equity-schedule-of-warrant-activity-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-5-stockholders-equity-tables" name="statement-statement-note-5-stockholders-equity-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-6-net-loss-per-share-schedule-of-basic-and-diluted-earnings-per-share-details" name="statement-statement-note-6-net-loss-per-share-schedule-of-basic-and-diluted-earnings-per-share-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-6-net-loss-per-share-tables" name="statement-statement-note-6-net-loss-per-share-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-8-fair-value-measurement-schedule-of-fair-value-measurement-of-financial-instruments-details" name="statement-statement-note-8-fair-value-measurement-schedule-of-fair-value-measurement-of-financial-instruments-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-note-8-fair-value-measurement-tables" name="statement-statement-note-8-fair-value-measurement-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="astc_statement-statement-significant-accounting-policies-policies" name="statement-statement-significant-accounting-policies-policies" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
</xsd:schema>
